Optical switches and logic gates employing same

An optical switch including a light passageway having a changeable cross-sectional area, an activation light responsive piezoelectric element associated with the light passageway, the activation light responsive piezoelectric element being operative to change its shape in response to activation light impinging thereon and a conductive element operatively associated with the piezoelectric element for enhancing activation light responsiveness thereof, the activation light responsive piezoelectric element being associated with the light passageway and being operative such that changes in the shape of the piezoelectric element cause changes in the changeable cross-sectional area of the light passageway sufficient to govern the passage of light along the light passageway. Logic gates and logic functionality employing an optical switch are also described.

FIELD OF THE INVENTION

The present invention relates to light activated switches and logic gates generally.

BACKGROUND OF THE INVENTION

The U.S. Patents of the present inventor, Dr. Gary Neal Poovey, U.S. Pat. Nos. 7,072,536 and 7,283,698, the disclosures of which are hereby incorporated by reference, together with the publications listed hereinbelow, the disclosures of which are hereby incorporated by reference, are believed to represent the current state of the art:

SUMMARY OF THE INVENTION

The present invention seeks to provide improved optical switches, logic gates and logic functionality.

There is thus provided in accordance with a preferred embodiment of the present invention an optical switch including:

a light passageway having a changeable cross-sectional area;

an activation light responsive piezoelectric element associated with the light passageway, the activation light responsive piezoelectric element being operative to change its shape in response to activation light impinging thereon; and

a conductive element operatively associated with the piezoelectric element for enhancing activation light responsiveness thereof,

the activation light responsive piezoelectric element being associated with the light passageway and being operative such that changes in the shape of the piezoelectric element cause changes in the changeable cross-sectional area of the light passageway sufficient to govern the passage of light along the light passageway.

Preferably, the light passageway, the piezoelectric element and the conductive element are configured and operative such that impingement of activation light within a first range of threshold levels on the piezoelectric element causes the light passageway to prevent passage of light of a first range of wavelengths therethrough and impingement of activation light within a second range of threshold levels, lying outside of the first range of threshold levels, on the piezoelectric element causes the light passageway to allow passage of light of a first range of wavelengths therethrough.

In accordance with a preferred embodiment of the present invention, the conductive element comprises a layer of a conductive material extending along a surface of the piezoelectric element.

Preferably, the piezoelectric element comprises at least two layers of piezoelectric material having different piezoelectric characteristics.

In accordance with a preferred embodiment of the present invention, the at least two layers of piezoelectric material have different crystal orientations.

Preferably, the conductive element is disposed between two layers of the piezoelectric element.

In accordance with a preferred embodiment of the present invention, there is also provided a light coupler operative to direct the activation light and signal light into the light pathway, at least one characteristic of the activation light governing whether the signal light passes through the passageway.

Additionally in accordance with a preferred embodiment of the present invention there is provided an optical switch including:

a light passageway having a changeable cross-sectional area; and

an activation light responsive piezoelectric element associated with the light passageway, the activation light responsive piezoelectric element being operative to change its shape in response to activation light impinging thereon,

the activation light responsive piezoelectric element including at least two layers of piezoelectric material having different piezoelectric characteristics, the piezoelectric element being associated with the light passageway and being operative such that changes in the shape of the piezoelectric element cause changes in the changeable cross-sectional area of the light passageway sufficient to govern the passage of light along the light passageway.

Preferably, the light passageway and the piezoelectric element are configured and operative such that impingement of activation light within a first range of threshold levels on the piezoelectric element causes the light passageway to prevent passage of light of a first range of wavelengths therethrough and impingement of activation light within a second range of threshold levels, lying outside of the first range of threshold levels, on the piezoelectric element causes the light passageway to allow passage of light of a first range of wavelengths therethrough.

Additionally in accordance with a preferred embodiment of the present invention there is provided a logic gate including at least one gate having at least one of NOT, AND, OR, NAND and NOR functionality including at least one optical switch actuated by light, the at least one optical switch including:

a signal light passageway having a changeable cross-sectional area; and

an activation light responsive piezoelectric element associated with the light passageway, the activation light responsive piezoelectric element being operative to change its shape in response to activation light impinging thereon;

the activation light responsive piezoelectric element being associated with the light passageway and being operative such that changes in the shape of the piezoelectric element cause changes in the changeable cross-sectional area of the light sufficient to govern the passage of signal light along the light passageway.

Preferably the logic gate also includes light conduits supplying the activation light to the at least one optical switch and which carry signal light which carries digital information to and from the at least one light switch.

In accordance with a preferred embodiment of the present invention, the signal light has a wavelength which is greater than that of the activation light.

Preferably, the signal light has a wavelength which is approximately twice that of the activation light.

In accordance with a preferred embodiment of the present invention, the signal light has a wavelength of 1500 nm. and the activation light has a wavelength of approximately 750 nm.

There is additionally provided in accordance with a preferred embodiment of the present invention a logic gate providing NOT functionality and wherein the at least one optical switch comprises a single optical switch and wherein the signal light has a wavelength of approximately twice that of the activation light.

There is additionally provided in accordance with a preferred embodiment of the present invention a logic gate providing AND functionality and wherein the at least one optical switch comprises a single optical switch and wherein the signal light has a wavelength greater than that of the activation light, the logic gate also including:

first and second logic inputs receiving signal light;

a first light conduit receiving a first portion of the signal light received at the first logic input;

a second light conduit receiving a second portion of the signal light received at the first logic input;

a third light conduit receiving a first portion of the signal light received at the second logic input;

a fourth light conduit receiving a second portion of the signal light received at the second logic input;

a first wavelength modifier operative to decrease the wavelength of the light along the second light conduit to the wavelength of the activation light;

a second wavelength modifier operative to decrease the wavelength of the light along the fourth light conduit to the wavelength of the activation light;

a first phase matcher operative to match the phase of the light along the second light conduit to that the activation light;

a second phase matcher which matches the phase of the light along the fourth light conduit to the activation light; and

a phase shifter operative to cause wavelength reduced and phase matched light along the second and fourth light conduits to be mutually out of phase by 180 degrees,

light along the first and third light conduits being supplied as a signal light input to the optical switch; and

wavelength reduced and phase matched light along the second and fourth light conduits being supplied together with additional activation light as activation light to the optical switch.

There is additionally provided in accordance with a preferred embodiment of the present invention a logic gate providing NAND functionality and wherein the first optical switch comprises a first optical switch and a second optical switch and wherein the signal light has a wavelength greater than that of the activation light, the logic gate also including:

first and second logic inputs receiving signal light inputs;

a first wavelength modifier operative to decrease the wavelength of signal light at the first input to the wavelength of the activation light;

a second wavelength modifier operative to decrease the wavelength of signal light at the second input to the wavelength of the activation light;

a third wavelength modifier operative to decrease the wavelength of signal light from the first optical switch;

a first light conduit supplying part of the light from the first wavelength modifier to a first light absorber;

a second light conduit supplying part of the light from the first wavelength modifier to the first optical switch;

a third light conduit supplying part of the light from the second wavelength modifier to a second light absorber;

a fourth light conduit supplying part of the light from the second wavelength modifier to the first optical switch;

a fifth light conduit supplying signal light from the first optical switch to the third wavelength modifier; and

a sixth light conduit supplying light wavelength modified light from the third wavelength modifier to the second optical switch as activation light.

There is additionally provided in accordance with a preferred embodiment of the present invention a logic gate providing OR functionality and wherein the at least one optical switch comprises a single optical switch and wherein the signal light has a wavelength greater than that of the activation light, the logic gate also including:

first and second logic inputs receiving signal light inputs;

a first wavelength modifier operative to decrease the wavelength of the light along the first light input to the wavelength of the activation light;

a second wavelength modifier operative to decrease the wavelength of the light along the second light input to the wavelength of the activation light;

a first phase matcher operative to match the phase of wavelength modified light from the first wavelength modifier to match the phase of actuation light;

a second phase matcher operative to match the phase of the light from the second wavelength modifier to match the phase of the actuation light;

a first light conduit supplying part of the light from the first phase matcher to a first light absorber;

a second light conduit supplying part of the light from the second phase matcher to a second light absorber;

a first phase shifter;

a second phase shifter;

a third light conduit supplying part of the light from the first phase matcher to the first phase shifter, thereby to cause light from the first phase matcher to be out of phase with the activation light; and

a fourth light conduit supplying part of the light from the second phase matcher to a second phase shifter, thereby to cause light from the first phase matcher to be out of phase with the supplied activation light,

a fifth light conduit supplying light from the first phase shifter to the optical switch; and

a sixth light conduit supplying light from the second phase shifter to the optical switch,

the optical switch receiving the activation light and signal light from the fifth and sixth light conduits.

There is additionally provided in accordance with a preferred embodiment of the present invention a logic gate providing OR functionality and wherein the at least one optical switch comprises first and second optical switches and wherein the signal light has a wavelength greater than that of the activation light, the logic gate also including:

first and second logic inputs receiving signal light inputs;

a first wavelength modifier operative to decrease the wavelength of the light along the first light input to the wavelength of the activation light;

a second wavelength modifier operative to decrease the wavelength of the light along the second light input to the wavelength of the activation light;

first and second light conduits supplying wavelength modified light from the first and second wavelength modifiers;

a power limiter receiving light from the first wavelength modifier and second wavelength modifier via the respective first and second light conduits and being operative to maintain light output therefrom at a predetermined power level;

a third light conduit supplying power limited light from the power limiter to the first optical switch;

a third wavelength modifier receiving signal light from the first optical switch and being operative to decrease the wavelength of the light to the wavelength of the activation light; and

a fourth light conduit supplying light from the third wavelength modifier to the second optical switch.

There is still further provided in accordance with a preferred embodiment of the present invention a logic gate providing OR functionality and wherein the at least one optical switch comprises a single optical switch and wherein the signal light has a wavelength greater than that of the activation light, the logic gate also including:

first and second logic inputs receiving signal light;

a first light conduit receiving a first portion of the signal light received at the first logic input;

a second light conduit receiving a second portion of the signal light received at the first logic input;

a third light conduit receiving a first portion of the signal light received at the second logic input;

a fourth light conduit receiving a second portion of the signal light received at the second logic input;

a first wavelength modifier operative to decrease the wavelength of the light along the second light conduit to the wavelength of the activation light;

a second wavelength modifier operative to decrease the wavelength of the light along the fourth light conduit to the wavelength of the activation light; and

a phase shifter operative to cause wavelength modified light from the first wavelength modifier to be out of phase by 180 degrees with respect to the light from the second wavelength modifier,

the optical switch receiving light from the first and third light conduits, the second wavelength modifier and the phase shifter.

Additionally there is provided a logic gate wherein the at least one optical switch is constructed as described hereinabove and logic functionality employing or more logic gates as described hereinabove.

Further in accordance with a preferred embodiment of the present invention there is provided an optical switch including:

a signal channel configured to guide a signal light;

a piezoelectric element adjacent to the signal channel; and

a conductive layer adjacent to the piezoelectric element;

wherein passage of the signal light through the signal channel is controlled by the application of an activation light to the piezoelectric element and wherein the conductive layer enhances an electrical field applied to the piezoelectric element in response to the activation light.

Preferably, the conductive layer is adhered to a surface of the piezoelectric element.

In accordance with a preferred embodiment of the present invention, application of the activation light to the piezoelectric element causes the shape of the piezoelectric element to change such that the signal light is not able to pass through the signal channel.

Preferably, the signal channel comprises a chamber that is filled with a compressible material.

Preferably, the piezoelectric element forms a portion of the chamber.

In accordance with a preferred embodiment of the present invention, the piezoelectric element comprises at least two layers that have different piezoelectric characteristics.

Preferably, the conductive layer is adhered between two layers of the piezoelectric element.

There is additionally provided in accordance with a preferred embodiment of the present invention a method for operating an optical switch, the method including:

applying a signal light to an optical switch that comprises a piezoelectric element and at least one conductive layer adjacent to the piezoelectric element; and

applying an activation light to the piezoelectric element to change the state of the optical switch;

wherein the conductive layer enhances an electrical field applied to the piezoelectric element in response to the applied activation light.

Preferably, applying the activation light to the piezoelectric element causes the shape of the piezoelectric element to change such that the signal light is not able to pass through the optical switch.

Preferably, applying the activation light comprises applying two light signals, which are out of phase with each other, to the piezoelectric element and then removing one of the light signals, leaving the remaining light signal as the activation light.

There is additionally provided a method for operating an optical switch, the method including:

applying a signal light to a signal channel, the signal channel being adjacent to a piezoelectric element that is adjacent to at least one conductive layer; and

applying an activation light to the piezoelectric element to change the shape of the piezoelectric element such that the signal light is prevented from passing through the signal channel,

wherein the conductive layer enhances an electrical field applied to the piezoelectric element in response to the applied activation light.

Additionally there is provided an optical switch including:

a signal channel configured to guide a signal light;

a piezoelectric element adjacent to the signal channel;

a conductive layer adjacent to the piezoelectric element; and

means for applying an activation light to the piezoelectric element to change the shape of the piezoelectric element such that the signal light is prevented from passing through the signal channel;

wherein the conductive layer enhances an electrical field applied to the piezoelectric element in response to the applied activation light.

There is additionally provided a method for operating an optical switch, the method including:

applying a signal light to an optical switch that comprises a piezoelectric element, the piezoelectric element including at least two layers of piezoelectric material that have different piezoelectric characteristics; and

applying an activation light to the piezoelectric element to change the state of the optical switch.

Preferably, applying the activation light to the piezoelectric element causes the shape of the piezoelectric element to change such that the signal light is not able to pass through the optical switch.

Preferably, the change in the shape of the piezoelectric element causes a change in a dimension of a signal channel of the optical switch.

In accordance with a preferred embodiment of the present invention, applying the activation light comprises applying two light signals, which are out of phase with each other, to the piezoelectric element and then removing one of the light signals, leaving the remaining light signal as the activation light.

In accordance with a preferred embodiment of the present invention, the conductive layer adjacent to the piezoelectric element enhances an electrical field applied to the piezoelectric element in response to the applied activation light.

There is also provided an optical switch including:

a signal channel configured to guide a signal light; and

a piezoelectric element adjacent to the signal channel, the piezoelectric element including at least two layers of piezoelectric material that have different piezoelectric characteristics;

wherein passage of the signal light through the signal channel is controlled by the application of an activation light to the piezoelectric element.

Preferably, application of the activation light to the piezoelectric element causes the shape of the piezoelectric element to change such that the signal light is not able to pass through the signal channel.

There is also provided a method for operating an optical switch, the method including:

applying a signal light to a signal channel, the signal channel being adjacent to a piezoelectric element that has at least two layers of piezoelectric material that have different piezoelectric characteristics; and

applying in activation light to the piezoelectric element to change the shape of the piezoelectric element such that the signal light is prevented from passing through the signal channel.

Additionally there is provided an optical switch including:

a signal channel configured to guide a signal light;

a piezoelectric element adjacent to the signal channel, the piezoelectric element including at least two different layers that have different piezoelectric characteristics; and

means for applying an activation light to the piezoelectric element to change the shape of the piezoelectric element such that the signal light is prevented from passing through the signal channel.

DETAILED DESCRIPTION OF THE INVENTION

Light actuated optical switches are used to construct AND, OR, and NOR logic gates. Light signals coming into the logic gates are processed so that the output of the logic gates conforms to the needed specification for each kind of gate. The light signals are all that are used to operate the logic gates, and no external battery is required using light actuated optical switches, the logic gates will have dimensions that will fit within semiconductor logic design dimensions.

Computers will be able to be made that function on light signals instead of electrical signals. Transistors of transistor based logic gates switch in 10E−9 seconds, and this limits the speed of transistor based logic gates. Light can travel three microns in 10E−14 seconds. Logic gates based on light actuated switches can be much faster than transistor based logic gates.

An optical switch includes a signal channel and a piezoelectric element that is adjacent to the signal channel. The piezoelectric element changes shape in response to an activation light and the piezoelectric element is configured relative to the signal channel such that the change in shape of the piezoelectric element causes a change in a dimension of the signal channel. For example, the change in shape of the piezoelectric element causes a dimension of the signal channel to be reduced far enough that a signal light is no longer able to pass through the signal channel. Using this phenomenon, the state of the optical switch is controlled by controlling the application of the activation light to the piezoelectric element. In an embodiment, the optical switch allows a signal light to pass through the signal channel when the activation light is not applied to the piezoelectric element and blocks the signal light from passing through the signal channel when the activation light is applied to the piezoelectric element. Because the shape of the piezoelectric element determines whether or not light passes through the signal channel, the function of the optical switch depends on the ability of the piezoelectric element to change shape.

In accordance with an embodiment of the invention, the piezoelectric element has at least two layers of piezoelectric material with each layer having different piezoelectric characteristics. The piezoelectric characteristics of the layers are selected to enhance the performance of the piezoelectric element and ultimately to enhance the performance of the optical switch. In an embodiment, the piezoelectric characteristics of the layers are selected to produce a piezoelectric element that exhibits sufficient shape change in response to an activation light to block a signal light from passing through a signal channel.

FIG. 1Adepicts an optical switch100that includes a signal channel102and a piezoelectric element104and that is controlled by an activation light. The signal channel guides the transmission of light within a confined area along a defined path. The signal channel is formed by a light guiding structure, or combination of structures, which can guide light within a confined area along a defined path. Structures that can form the signal channel include, for example, an optical fiber, substrates such as lithium niobate or other transparent piezoelectric materials that include a signal channel, an optical waveguide, and a chamber for holding a compressible material. In the embodiment ofFIG. 1A, the signal channel is formed by a monolithic light guiding element.

The piezoelectric element104is formed of piezoelectric material. Examples of piezoelectric material that can be used to form the piezoelectric element include crystalline piezoelectric material such as quartz (SiO2), lithium niobate (LiNbO3), lead zirconate (PbZrO3), lead titanate (PbTiO3), and lead zirconate titanate. Examples of piezoelectric materials that can be oriented in a magnetic field are lead zirconate and lead titanate or lead zicronate titanate. Quartz and lithium niobate are examples of transparent piezoelectric materials.

The piezoelectric element104has at least two layers106and108of piezoelectric material having different piezoelectric characteristics. The different piezoelectric characteristics of the different layers may include, for example: 1) different degrees of expansion and/or shrinkage in response to the same electrical field; 2) different responses to the same electrical field, for example, one of the layers expands in response to an electrical field having a first orientation and the other layer expands in response to an electrical field having a second orientation that is perpendicular to the first orientation; 3) different polarities; 4) different strains; 5) different hysteresis; 6) different capacitances; 7) different impedances; 8) different resistivities; 9) different thermal histories; and 10) different electromagnetic histories.

The piezoelectric characteristics of a piezoelectric material are a function of, for example: 1) the type of piezoelectric material; 2) the crystal orientation of the piezoelectric material; 3) doping levels within the piezoelectric material; 4) the density of the piezoelectric material; 5) the void density of the piezoelectric material; 6) the chemical constituency of the piezoelectric material; 7) the thermal history of the piezoelectric material; 8) the electromagnetic history of the piezoelectric material. The desired piezoelectric characteristic of each layer of piezoelectric material can be achieved by, for example, manipulating one or more of the above-identified parameters.

In an embodiment, layers of piezoelectric material that exhibit different degrees of expansion and/or shrinkage in response to the same electrical field are integrated into a piezoelectric element to cause the piezoelectric element to change shape or bend in response to the activation light. For example, if two adjacent layers of a piezoelectric element, which are adhered to each other into a monolithic element, expand different amounts in response to the same activation light, the piezoelectric element will bend. In an embodiment, the piezoelectric element includes at least two layers of piezoelectric material, having different piezoelectric characteristics, which are formed as a monolithic element. For example, the piezoelectric element is formed by building layers of piezoelectric material on top of each other using semiconductor processing techniques, e.g., crystal growth, deposition, sputtering, ion implantation, etc. In an embodiment, the layers of the piezoelectric element have different crystal orientations so that the two layers respond differently to the same electrical field. For example, the two layers have crystal orientations that are perpendicular to each other. In another embodiment, at least one of the layers of the piezoelectric element is made of an organic material.

Using a piezoelectric element with layers of piezoelectric material having different piezoelectric characteristics, the response of the piezoelectric element can be selected to optimize on/off switching. For example, the piezoelectric characteristics of the layers can be selected to: 1) maximize the shape change of the piezoelectric element in response to the activation light; 2) minimize hysteresis; 3) reduce the amount of power required to change the shape of the piezoelectric element; and 4) reduce the amount of heat generated by the switching technique.

Operation of the optical switch100depicted inFIG. 1Ais now described with reference toFIGS. 1A and 1B.FIG. 1Aillustrates the piezoelectric element104in a non-activated state. In the non-activated state, the shape of the piezoelectric element is unchanged from its normal state, where the normal state of the piezoelectric element is the state of the element in the absence of an activation light. In the embodiment ofFIG. 1A, the piezoelectric element is basically flat in the non-activated state. The flat shape of the piezoelectric element allows a signal light110to pass through the signal channel104as indicated by the signal light entering and exiting the signal channel.

FIG. 1Billustrates the piezoelectric element104in an activated state that results from the application of an activation light112to the piezoelectric element. In the embodiment ofFIG. 1B, the activation light is applied to the piezoelectric element by directing the activation light into the signal channel102in parallel with the signal light110. The activation light supplies an electrical field that effects the piezoelectric material. In the activated state, the shape of the piezoelectric element changes shape enough that the signal light is blocked from passing through the signal channel. The blocking of the signal light is indicated by the lack of the signal light exiting the signal channel. Once the activation light is removed from the signal channel, the piezoelectric element returns to its normal shape and the signal light is able once again to pass through the signal channel.

As described above, activation of the piezoelectric element104in response to the activation light112causes the shape of the piezoelectric element to change, thereby causing at least one dimension of the signal channel102to change.FIG. 2Ais a cross-sectional view of the signal channel and the piezoelectric element ofFIG. 1Awhen the piezoelectric element is in a non-activated state.FIG. 2Bis a cross-sectional view of the signal channel and the piezoelectric element ofFIG. 1Bwhen the piezoelectric element is in an activated state. In the activated state, the piezoelectric element extends into the signal channel and reduces at least one dimension of the signal channel. As illustrated inFIGS. 2A and 2B, the cross-sectional area of the signal channel is smaller in the activated state (FIG. 2B) than it is in the non-activated state (FIG. 2A).

As seen in the embodiment ofFIGS. 1A-2B, there is still an opening in the signal channel102even when the piezoelectric element104is in the activated state. Although there is still an opening in the signal channel even when the piezoelectric element is in the activated state, the opening in the signal channel is small enough that the signal light110is blocked from passing through the signal channel. The ability of a signal light to pass through the signal channel is a function of the dimensions of the signal channel and of the wavelength of the signal light. In general, light having a shorter wavelength is able to pass through a signal channel with a smaller dimension than light having a longer wavelength.

FIG. 3depicts a graph of optical signal attenuation vs. a dimension of a signal channel. As illustrated inFIG. 3, the optical signal attenuation changes rapidly once the signal channel dimension reaches a certain dimension, referred to herein as the cutoff dimension. For example, at a dimension smaller than the cutoff dimension (e.g., about 5 angstroms), the attenuation rapidly rises and at a dimension larger than the cutoff dimension, the attenuation rapidly falls. The sharp response to a change in the signal channel dimension around the cutoff dimension, as indicated inFIG. 3, enables fast on/off switching by toggling the activation light such that a dimension of the signal channel switches between being larger or smaller than the cutoff dimension.

As described above, the state of the optical switch100is activated by applying an activation light112to the piezoelectric element104. Activation light can be applied to the piezoelectric element using different techniques. Some exemplary techniques for applying activation light to the piezoelectric element are described with reference toFIGS. 4A-5B.

FIGS. 4A and 4Billustrate a technique for changing the state of optical switch100that involves applying an activation light112having a shorter wavelength than the signal light110. Referring toFIG. 4A, the optical switch100is in an on state when no activation light is applied to the piezoelectric element104and the signal light110passes through the signal channel102. As illustrated inFIG. 4B, activation light112is applied to the piezoelectric element104to change the state of the optical switch100from on to off. In the off state, the activation light112causes the piezoelectric element104to change shape and block the passage of the signal light110through the signal channel102. In this example, the activation light112has a shorter wavelength than the signal light110. In particular, the wavelength of the activation light112is short enough that the activation light112is still able to pass through the signal channel even when the optical switch100is in an off state.FIG. 4Billustrates the case in which the activation light112, which has a shorter wavelength than the signal light110, is able to pass through the signal channel102even when the optical switch100is in the off state.

FIGS. 5A and 5Billustrate a technique for changing the state of an optical switch100in which applying the activation light involves providing two light signals112A and112B, which are out of phase with each other, to the piezoelectric element104and then removing one of the light signals, light signal112A in the illustrated embodiment, leaving the remaining light signal, light signal112B in the illustrated embodiment, as the activation light. In this embodiment, the two signals112A and112B are out of phase with each other such that their electrical fields effectively cancel each other out (e.g., 180 degrees out of phase). Because the two out of phase signals cancel each other out, while the two out of phase signals are simultaneously applied to the piezoelectric element104, the piezoelectric element104is not activated. Once one of the light signals is removed, the electrical field of the remaining light signal is no longer canceled out and the remaining light signal activates the piezoelectric element.FIG. 5Aillustrates the signal light110and both components of the out of phase light signals112A and112B passing through the signal channel102. As described above, the piezoelectric element104is not activated in this case because the two out of phase light signals cancel each other out. InFIG. 5B, one of the out of phase light signals112A is removed, leaving the remaining light signal112B as the activation light. The activation light activates the piezoelectric element104and blocks the passage of the signal light110(and the activation light in this case) through the signal channel. In another embodiment, the power of one of the two light signals can be increased above the other light signal to overcome the canceling effect thereby providing the activation light.

Another technique for optimizing the performance of a light activated optical switch is to enhance the electrical field that is applied to the piezoelectric element in response to the activation light. In accordance with an embodiment of the invention, at least one conductive layer is located adjacent to the piezoelectric element of a light activated optical switch to enhance the electrical field that is applied to the piezoelectric element in response to the activation light. The conductive layer has free electrons or electron holes that are drawn to and collect at a surface adjacent to the piezoelectric element when the activation light is applied to the piezoelectric element. The collection of free electrons near the piezoelectric element enhances the electrical field that is applied to the piezoelectric element in response to the activation light. The enhanced electrical field can be used to enhance the performance of the piezoelectric element and ultimately to enhance the performance of the optical switch. For example, the enhanced electrical field contributed from the adjacent conductive layer enables the piezoelectric element to be activated with lower power and/or quicker than is possible when there is not a conductive layer adjacent to the piezoelectric element.

Without the conductive layer the electric field of the activation light alone activates the piezoelectric element. When a conductive layer is used, the conductive layer supplies charges that are gathered or dispersed by the electric field of the activation light. The electric field of the gathered charges adds to the electric field of the activation light. In this case, the piezoelectric element is acted upon by the electric field of the activation light and the electric field of the gathered charges. In the case of dispersed charges, matter is composed of positive and negative charges so when one is dispersed the other is expressed. In this case the electric field of the expressed charges adds to the electric field of the activation light and the effect on the piezoelectric element is enhanced. Electrons move in metal conductors, but positive holes can move in a semiconductor.

FIG. 6Adepicts an embodiment of a light activated optical switch120that includes a signal channel122, a piezoelectric element124, and a conductive layer126adjacent to the piezoelectric element124. The signal channel122and piezoelectric element124are similar to those described above, although the piezoelectric element124does not necessarily include different layers of piezoelectric material having different piezoelectric characteristics. The conductive layer126is a highly conductive material such as lead, tungsten, other metals, silicon doped with boron, silicon doped with arsenic, doped gallium arsenide, and/or other semiconductor materials. In an embodiment, the conductive layer126is adhered to a surface of the piezoelectric element124. For example, the conductive layer126may be deposited on a major surface of the piezoelectric element124using a metal deposition technique. In an alternative embodiment, the conductive layer126is formed of a semiconductor material with positive or negative charges that move instead of only negative charges.

Operation of the optical switch120depicted inFIG. 6Ais now described with reference toFIGS. 6A and 6B.FIG. 6Aillustrates the piezoelectric element124in a non-activated state. In the non-activated state, the shape of the piezoelectric element124is unchanged from its normal state, where the normal state of the piezoelectric element124is the state of the element in the absence of an activation light. In the embodiment ofFIG. 6A, the piezoelectric element124is basically flat in the non-activated state. The flat shape of the piezoelectric element allows a signal light128to pass through the signal channel122as indicated by the signal light128entering and exiting the signal channel122.

FIG. 6Billustrates the piezoelectric element124in an activated state that results from the application of an activation light129to the piezoelectric element124. In the embodiment ofFIG. 6B, the activation light129is applied to the piezoelectric element124by directing the activation light129into the signal channel122in parallel with the signal light128. When the activation light129is applied to the piezoelectric element, free electrons are drawn to the surface of the conductive layer126that is nearest the piezoelectric element124. In the activated state, the shape of the piezoelectric element124changes shape enough that the signal light128is blocked from passing through the signal channel122. The blocking of the signal light128is indicated by the lack of the signal light128exiting the signal channel122. The additional electrons near the piezoelectric material, which are associated with the conductive layer126, cause an increase in the electric field that is applied to the piezoelectric material of piezoelectric element124. The increase in the electrical field that is associated with the conductive layer126provides benefits that include, for example, increasing the magnitude of the change in shape of the piezoelectric element124, increasing the speed at which the piezoelectric element124changes shape, and/or reducing the amount of activation light required to achieve the desired shape change.

FIG. 7illustrates the action of an electrical field130of the activation light129on the electrons of the conductive layer126ofFIGS. 6A and 6B. InFIG. 7, surface132is the surface of the conductive layer126nearest the activation light129and the surface134is the surface of the conductive layer126farthest from the activation light129. The comb-like structure inFIG. 7represents the electrical field under the influence of the conductive layer126. Each tooth136of the comb-like structure represents a portion of the electrical field and some of the teeth have wide extensions138at their ends. These wide extensions138represent the larger field that is contributed by the charges that move in the conductive layer126that is adjacent to the piezoelectric element124. The charges that move in response to the electric field of the activation light129are represented by dashed lines140. When the electric field is negative the charges in the conductive layer126are driven away from the near surface132of the conductive layer and enhance the negative field. When the electric field is positive the charges in the conductive layer come to the near surface132of the conductive layer and enhance the electric field. If the conductive layer126is not present, no charges would move because piezoelectric materials are not conductors but dielectric materials. Referring toFIG. 7, if the conductive layer126was removed leaving only a piezoelectric element (not shown), the teeth136on the comb like structure would have no extensions138on them.

FIG. 8depicts an optical switch system150that includes a light activated optical switch152as described above with reference toFIGS. 1A-7. The optical switch system150ofFIG. 8also includes an activation light system154, which includes an activation light source156and an activation light controller158. The optical switch system150is optically connected to a signal light source160to receive a signal light161. In the embodiment ofFIG. 8, the signal light161is provided to the optical switch152via a signal light path162and an activation light163is provided to the optical switch152via an activation light path164and the signal light path162. The signal light161and activation light163are combined at a coupler166. The output of the optical switch152goes through an output path168.

The activation light system154controls the application of activation light163to the piezoelectric element (not shown) of the optical switch152. In the embodiment ofFIG. 8, the activation light source156is a light source such as a light emitting diode (LED) or a laser that generates an activation light with the desired characteristics, e.g., the desired wavelength, intensity, phase of the activation light in relation to the other light in the signal channel, and polarization, and the activation light controller158controls the transmission of the activation light163from the activation light system. In an embodiment, the intensity of the activation light163must be great enough to sufficiently change the shape of the piezoelectric element of the optical switch152and in an embodiment, the intensity of the activation light163is greater than the intensity of the signal light161. The wavelength of the activation light163can be shorter or longer than the wavelength of the signal light161. As described above, if the wavelength of the activation light163is short enough, the activation light163may pass through the signal channel even when the piezoelectric element is activated and the signal light163is blocked.

The activation light system154can be configured to provide the activation light163to the optical switch152in many different ways. For example, in one embodiment, the activation light163is switched on and off by a second light activated optical switch, in another embodiment the angle of a mirror is changed to provide the activation light163, in another embodiment, an LED or laser is turned on/off, and in other embodiments, other switches may be employed to control the activation light163. The signal light source160generates the signal light161that is switched on and off by the optical switch152(i.e., allowed to pass through the optical switch152and blocked from passing through the optical switch152). In an embodiment, the signal light source160is an optical transmitter that transmits digital data by modulating an optical signal (e.g., frequency or amplitude modulation). In an embodiment, the signal light161that is output by the signal light source160is an optical signal that communicates digital data in some way (e.g., amplitude or frequency modulation, logic, etc.) while the activation light163that is output by the activation light source156does not communicate digital data. For example, the signal light161may carry digital data in a modulated light format while the activation light163is not modulated to carry digital data.

In operation, the signal light161is provided to the optical switch152via the signal light source160and the application of the activation light163to the piezoelectric element of the optical switch152is controlled by the activation light system154. In one embodiment, the signal light161passes through the optical switch152when the activation light system154does not provide an activation light163to the optical switch152and is blocked from passing through the optical switch152when the activation light system154does provide an activation light163to the optical switch152.

In the optical switches described with reference toFIGS. 1A-6B, the signal light and activation light are transmitted in the same signal channel. Various techniques can be used to combine the signal light and the activation light into the same signal channel.FIG. 9depicts an embodiment of an optical switch152and an optical coupler166that is used to couple the signal light161and the activation light163into the same signal channel122. In the embodiment ofFIG. 9, the signal light161travels in signal light path162, such as a signal fiber, and the activation light163travels in activation light path164, such as an activation fiber. The signal light161and activation light163are coupled into the signal channel122by the optical coupler166. It is appreciated that, although in the illustrated embodiment ofFIG. 9an optical coupler is shown, other suitable techniques for coupling the signal light161and the activation light163into the same signal channel122can be used.

FIGS. 10A-10Edepict different embodiments of the light activated optical switches described above with reference toFIGS. 1A-9.FIG. 10Adepicts an embodiment of a light activated optical switch170in which the piezoelectric element172has more than two layers174of piezoelectric material with different piezoelectric characteristics. In the illustrated embodiment ofFIG. 10, the piezoelectric element172has four layers174of piezoelectric material. In one embodiment, the different layers174of piezoelectric material each have a different piezoelectric characteristic and in another embodiment, the different layers of piezoelectric material have alternating piezoelectric characteristics. It should be understood that the number and arrangement of piezoelectric layers174can include many different variations.

FIG. 10Bdepicts an embodiment of a light activated optical switch176in which a conductive layer178is sandwiched between two layers180of a piezoelectric element182. This embodiment allows the piezoelectric element182to be oriented by placing charges on the conductive layer178and causes the change in shape of each layer180of the piezoelectric element182to be enhanced because of the proximity of the piezoelectric layers180to the conductive layer178.

FIG. 10Cdepicts an embodiment of a light activated optical switch184in which multiple conductive layers185are sandwiched between multiple different layers186of the piezoelectric element187. In this example, the conductive layers185are alternately adhered between different layers186of the piezoelectric element187. The multiple layers185of conductive material between the piezoelectric layers186allow each layer186of piezoelectric material to be polarized individually to different orientations by applying a charge to the conductive layers185. This enables the action of the piezoelectric layers186working against each other to accentuate the change in shape of the piezoelectric element187.

In general, the multiple conductive layers allow the hysteresis of the piezoelectric element to be managed. The multiple conductive layers allow a reduction in the temperature that the piezoelectric element must be raised to in order to change the orientation of the piezoelectric material. The multiple conductive layers allow the change in shape of the piezoelectric element to be enhanced. The multiple conductive layers allow the management of many mechanical, electrical, thermal, and other physical characteristics of the optical switch to be managed to make the optical switch easier to be constructed, maintained, and used. In an embodiment, the different layers of piezoelectric material and the conductive layers are formed in a monolithic stack structure. The monolithic stack structure can be formed, for example, using known semiconductor processing techniques, e.g., crystal growth, metal deposition, sputtering, ion implantation, etc.

In some cases, the hysteresis of a piezoelectric element can limit how quickly a light activated optical switch, which is made with a piezoelectric element, can be changed from one state to another. In an embodiment, a 3000 angstroms thick layer of lead zirconate titonate (PZT) is deposited on a substrate. The layer of PZT has a given percentage of lead and a given percentage of zirconium and titanium. Next, a 3000 angstrom layer of PZT is deposited on the first layer, with this layer having more lead and zirconium while reducing the percentage of titanium on top of that. Using these layers, the hysteresis that the resulting piezoelectric element displays is reduced in comparison to a piezoelectric element that does not include similar layers. If more alternating layers are deposited to build up a piezoelectric element, a quickly responding piezoelectric element can be fabricated. If all of this is deposited upon a conductive layer, the electric field of the activation light is enhanced to make a light activated optical switch that responds even faster.

FIG. 10Ddepicts an embodiment of a light activated optical switch188that includes a multilayer piezoelectric element189on one side of the signal channel190and conductive layers191on two sides of signal channel190. The response of the switch is enhanced by a multiplicity of conductive layers191.

FIG. 10Edepicts an embodiment of a light activated optical switch192that includes a multilayer piezoelectric element194and a conductive layer196on two sides of a signal channel198. In an embodiment,FIG. 10Erepresents a cross-sectional view of an optical fiber that includes a piezoelectric element and a conductive layer formed in a band entirely around the circumference of the optical fiber. In this embodiment, the fiber is a compressible material.

FIG. 11Adepicts an embodiment of a light activated optical switch200that includes a signal channel202, a piezoelectric element204, and a conductive layer206, where a portion of the signal channel includes a chamber208that is filled with a compressible material. The compressible material may be, for example, a gas such as argon or nitrogen or a material such as a petroleum distillate or a silicon rubber. The chamber208filled with the compressible material is adjacent to the piezoelectric element204such that the piezoelectric element204can expand into the chamber208when activated by an activation light. In an embodiment, the piezoelectric element204forms a portion of the chamber208. In an embodiment, at least a portion of the chamber204is formed by a transparent material.

Operation of the optical switch200depicted inFIG. 11Ais now described with reference toFIGS. 11A and 11B.FIG. 11Aillustrates the piezoelectric element204in a non-activated state. In the non-activated state, the shape of the piezoelectric element204is unchanged from its normal state, where the normal state of the piezoelectric element204is the state of the element in the absence of an activation light. In the embodiment ofFIG. 11A, the piezoelectric element204is basically flat in the non-activated state and does not protrude into the chamber208. The flat shape of the piezoelectric element204allows a signal light210to pass through the signal channel202(including the chamber208) as indicated by the signal light210entering and exiting the signal channel202.

FIG. 11Billustrates the piezoelectric element204in an activated state that results from the application of an activation light212to the piezoelectric element204. In the embodiment ofFIG. 11B, the activation light212is applied to the piezoelectric element204by directing the activation light212into the signal channel202in parallel with the signal light210. When the activation light212is applied to the piezoelectric element204, the piezoelectric element204protrudes into the chamber208, thereby compressing the compressible material within the chamber. In the activated state, the shape of the piezoelectric element204changes enough that the signal light210is blocked from passing through the signal channel202. The blocking of the signal light210is indicated by the lack of the signal light210exiting the signal channel202. When the activation light212is removed from the signal channel202, the piezoelectric element204returns to its normal state allowing the signal light210to pass. In the absence of the activation light212, the pressure of the compressed material within the chamber208helps to return the piezoelectric element204to its normal state.

FIG. 12Adepicts an embodiment of a light activated optical switch220that includes a signal channel222, a piezoelectric element224, and a conductive layer226adjacent to the piezoelectric element in which the signal channel222is an optical fiber and the piezoelectric element224and conductive layer226are formed in a band entirely around the circumference of the optical fiber.FIG. 12Aillustrates the piezoelectric element224in a non-activated state. In the non-activated state, the shape of the piezoelectric element224is unchanged from its normal state, where the normal state of the piezoelectric element224is the state of the element in the absence of an activation light. In the embodiment ofFIG. 12A, the piezoelectric element224is basically flat in the non-activated state. The flat shape of the piezoelectric element224allows a signal light230to pass through the signal channel222as indicated by the signal light230entering and exiting the signal channel222.FIG. 12Billustrates the piezoelectric element224in an activated state that results from the application of an activation light232to the piezoelectric element224. In the embodiment ofFIG. 12B, the activation light232is applied to the piezoelectric element224by directing the activation light232into the signal channel222in parallel with the signal light230. In the activated state, the shape of the piezoelectric element224changes enough that the signal light230is blocked from passing through the signal channel222. For example, the change in shape of the piezoelectric element224has the effect of squeezing the optical fiber like a belt to choke the passage of the signal light230. The blocking of the signal light230is indicated by the lack of the signal light230exiting the signal channel222. Once the activation light232is removed from the signal channel222, the piezoelectric element224returns to its normal shape and the signal light230is able once again to pass through the signal channel222.

FIG. 13Adepicts an embodiment of a light activated optical switch240that includes a signal channel242, a piezoelectric element244, and a conductive layer246adjacent to the piezoelectric element244in which the piezoelectric element244is made of a transparent material and forms at least a portion of the signal channel242.FIG. 13Aillustrates the piezoelectric element244in a non-activated state. In the non-activated state, the shape of the piezoelectric element244is unchanged from its normal state, where the normal state of the piezoelectric element244is the state of the element in the absence of an activation light. In the embodiment ofFIG. 13A, the piezoelectric element244is basically flat in the non-activated state. The flat shape of the piezoelectric element244allows a signal light250to pass through the signal channel242as indicated by the signal light250entering and exiting the signal channel242.FIG. 13Billustrates the piezoelectric element244in an activated state that results from the application of an activation light252to the piezoelectric element. In the embodiment ofFIG. 13B, the activation light252is applied to the piezoelectric element244by directing the activation light252into the signal channel242in parallel with the signal light250. In the activated state, the shape of the piezoelectric element244changes enough that the signal light250is blocked from passing through the signal channel242. For example, the change in shape of the piezoelectric element244has the effect of squeezing the signal channel242like a belt to choke the passage of the signal light250. The blocking of the signal light250is indicated by the lack of the signal light250exiting the signal channel242. Once the activation light252is removed from the signal channel242, the piezoelectric element244returns to its normal shape and the signal light250is able once again to pass through the signal channel242.

In an embodiment, the piezoelectric element and the signal channel are configured relative to each other such that application of the activation light changes the state of the optical switch from off (light is blocked) to on (light passes through the signal channel) instead of from on to off.

Some piezoelectric materials have a crystal orientation that must be aligned with the electric field that will cause it to change shape. Other piezoelectric materials can be heated up in a magnetic field and oriented to respond in the desired direction to the electric field that will be applied. In constructing a light activated optical switch, the orientation of the crystal or the magnetic orientation of the piezoelectric material should be directed to have the maximum shape change at right angles (that is perpendicular) to the direction of the signal light in the signal channel. In an embodiment, the electric field that triggers the switching is at right angles (that is perpendicular) to the path of the light in the light channel.

A description of a desired interaction follows. The electric field in volts needed to activate a light activated optical switch is calculated using the power in watts of the light in the channel. The Poynting vector equation which is written E=(2μoc P)1/2is used to make this calculation. Where μois 4 pi×10E−7 Weber/amp-meter, c is 3×10E+8 meters/second, E is the electric field in volts, and P is power in watts. Using this relation, it is found that the voltage developed by a 150-milliwatt signal in a fourth of a micron channel is 10 volts. In an embodiment, this voltage is employed to activate a light triggered optical switch to turn on or off the switch (e.g., allow the signal light to pass through the signal channel or to block the signal light from passing through the signal channel). An example of the size change that 10 volts could cause is as follows: In a channel that is 2065 angstroms in height, 10 volts will change that size by 40 angstroms when lead zicronate titonate is used. Lead zicronate titonate has a piezoelectric strain coefficient of 3.90 times 10E−10 meters/volt. 818 nm light (8180 angstroms), commonly used for fiber optics, will be able to travel in a channel just bigger than 2045 angstroms and will not travel down a channel smaller. When the 2065 angstroms channel changes to 2014 angstroms, the signal light will be blocked. Light of 8056 angstroms wavelength or shorter could still pass through the signal channel. The light activated optical switch can be turned on or off at a rate in 10E−11 seconds or faster. It makes use of effects that the electric and magnet fields of the light have on the medium through which the light travels. The equation for the attenuation (A) of the signal inside a wave-guide, which will give the decibels of attenuation per mile of travel for the signal is as follows:
A=(K/a3/2)((1/2)(f/fo)3/2+(f/fo)−1/2)/((f/fo)2−1)−1/2eq. (1)

The K is a constant for the material that the walls of the channel are made of; the value of K is 821.3 for lead. Since in an embodiment, only one wall of the optical switch is mostly lead, the optical switch may not follow exactly the graph ofFIG. 3, but the graph is given for illustrative purposes. The lower case “a” in the equation is the length of a side of the wave-guide. The frequency (f) of the signal being considered is in ratio against the cutoff frequency (fo) in the channel. This equation is for the TE0,1mode of wave propagation. In an embodiment, the sizes of the waveguides are chosen so that this is the only mode possible. As this relation is studied for shrinking waveguide dimensions for a given signal, the attenuation increases as the size of the signal channel shrinks and proceeds to infinity as the cutoff frequency is reached. This equation is on page 263 of Radio Engineers' Handbook written by Frederick Terman, and published by McGraw-Hill Book Company, Inc, 1943.

Reference is now made toFIG. 14A, which illustrates an optical switch300that includes a signal channel302and a plurality of piezoelectric elements which are preferably unevenly spaced along the length of the signal channel302. In the illustrated embodiment three generally rectangular piezoelectric elements304,305and306are distributed along the length of the signal channel302with non-uniform spacing therebetween. The shape of the piezoelectric elements304,305and306is controlled by an activation light. The signal channel302guides the transmission of light within a confined area along a defined path. The signal channel302is formed by a light guiding structure, or combination of structures, which can guide light within a confined area along a defined path. Structures that can form the signal channel include, for example, an optical fiber, substrates such as lithium niobate or other transparent piezoelectric materials that include a signal channel, an optical waveguide, and a chamber for holding a compressible material. In the embodiment ofFIG. 14A, the signal channel302is preferably formed by a monolithic light guiding element.

The piezoelectric elements304,305and306are preferably formed of piezoelectric material. Examples of piezoelectric material that can be used to form the piezoelectric elements include crystalline piezoelectric material such as quartz (SiO2), lithium niobate (LiNbO3), lead zirconate (PbZrO3), lead titanate (PbTiO3), and lead zirconate titanate. Examples of piezoelectric materials that can be oriented in a magnetic field are lead zirconate and lead titanate or lead zicronate titantae. Quartz and lithium niobate are examples of transparent piezoelectric materials.

The piezoelectric elements304,305and306preferably each include at least two layers307and308of piezoelectric material having different piezoelectric characteristics. The different piezoelectric characteristics of the different layers307and308may include, for example: 1) different degrees of expansion and/or shrinkage in response to the same electrical field; 2) different responses to the same electrical field, for example, one of the layers expands in response to an electrical field having a first orientation and the other layer expands in response to an electrical field having a second orientation that is perpendicular to the first orientation; 3) different polarities; 4) different strains; 5) different hysteresis; 6) different capacitances; 7) different impedances; 8) different resistivities; 9) different thermal histories; and 10) different electromagnetic histories.

Operation of the optical switch300depicted inFIG. 14Ais now described with additional reference toFIG. 14B.FIG. 14Aillustrates the piezoelectric elements304,305and306in a non-activated state. In the non-activated state, the shape of the piezoelectric elements304,305and306is unchanged from its normal state, where the normal state of the piezoelectric elements304,305and306is the state of the element in the absence of an activation light. In the embodiment ofFIG. 14A, the piezoelectric elements304,305and306are basically flat in the non-activated state. The flat shape of the piezoelectric elements304,305and306allows a signal light310to pass through the signal channel302as indicated by the signal light310entering and exiting the signal channel302.

FIG. 14Billustrates the piezoelectric elements304,305and306in an activated state that results from the application of an activation light312to the piezoelectric elements304,305and306. In the embodiment ofFIG. 14B, the activation light312is applied to the piezoelectric elements304,305and306by directing the activation light312into the signal channel302in parallel with the signal light310. The activation light312supplies an electrical field that effects the piezoelectric material. In the activated state, the shape of the piezoelectric elements304,305and306changes enough so that the signal light310is blocked from passing through the signal channel302. The blocking of the signal light310is indicated by the lack of the signal light310exiting the signal channel302. Once the activation light312is removed from the signal channel302, the piezoelectric elements304,305and306return to normal shape and the signal light310is able once again to pass through the signal channel302.

As described above, activation of the piezoelectric elements304,305and306in response to the activation light312causes the shape of the piezoelectric elements304,305and306to change, thereby causing at least one dimension of the signal channel302to change.FIG. 15Ais a cross-sectional view of the signal channel302and the piezoelectric element305ofFIG. 14Awhen the piezoelectric element305is in a non-activated state.FIG. 15Bis a cross-sectional view of the signal channel302and the piezoelectric element305ofFIG. 14Bwhen the piezoelectric element305is in an activated state. In the activated state, the piezoelectric element305extends into the signal channel302and reduces at least one dimension of the signal channel302. As illustrated inFIGS. 15A and 15B, the cross-sectional area of the signal channel302is smaller in the activated state (FIG. 15B) than it is in the non-activated state (FIG. 15A).

As seen in the embodiment ofFIGS. 14A-15B, there is still an opening in the signal channel302even when the piezoelectric elements304,305and306are in the activated state. Although there is still an opening in the signal channel302even when the piezoelectric elements304,305and306are in the activated state, the opening in the signal channel302is small enough that the signal light310is blocked from passing through the signal channel302. The ability of a signal light310to pass through the signal channel302is a function of the dimensions of the signal channel302and of the wavelength of the signal light310. In general, light having a shorter wavelength is able to pass through a signal channel302having a smaller dimension than light having a longer wavelength.

Reference is now made toFIG. 16Awhich illustrates an optical switch400that includes a signal channel402and a plurality of piezoelectric elements which are preferably unevenly spaced along the length of the signal channel402. In the illustrated embodiment, four generally circular cylindrical piezoelectric elements404,405,406and407are distributed along the length of the signal channel402with non-uniform spacing therebetween. The shape of the piezoelectric elements404,405,406and407is controlled by an activation light. The signal channel402guides the transmission of light within a confined area along a defined path. The signal channel is formed by a light guiding structure, or combination of structures, which can guide light within a confined area along a defined path. Structures that can form the signal channel include, for example, an optical fiber, substrates such as lithium niobate or other transparent piezoelectric materials that include a signal channel, an optical waveguide, and a chamber for holding a compressible material. In the embodiment ofFIG. 16A, the signal channel402is preferably formed by a monolithic light guiding element.

The piezoelectric elements404,405,406and407are preferably formed of piezoelectric material. Examples of piezoelectric material that can be used to form the piezoelectric element include crystalline piezoelectric material such as quartz (SiO2), lithium niobate (LiNbO3), lead zirconate (PbZrO3), lead titanate (PbTiO3), and lead zirconate titanate. Examples of piezoelectric materials that can be oriented in a magnetic field are lead zirconate and lead titanate or lead zicronate titantae. Quartz and lithium niobate are examples of transparent piezoelectric materials.

The piezoelectric elements404,405,406and407preferably each include at least two layers408and409of piezoelectric material having different piezoelectric characteristics. The different piezoelectric characteristics of the different layers may include, for example: 1) different degrees of expansion and/or shrinkage in response to the same electrical field; 2) different responses to the same electrical field, for example, one of the layers expands in response to an electrical field having a first orientation and the other layer expands in response to an electrical field having a second orientation that is perpendicular to the first orientation; 3) different polarities; 4) different strains; 5) different hysteresis; 6) different capacitances; 7) different impedances; 8) different resistivities; 9) different thermal histories; and 10) different electromagnetic histories.

Operation of the optical switch400depicted inFIG. 16Ais now described with additional reference toFIG. 16B.FIG. 16Aillustrates the piezoelectric elements404,405,406and407in a non-activated state. In the non-activated state, the shape of the piezoelectric elements404,405,406and407is unchanged from its normal state, where the normal state of the piezoelectric elements404,405,406and407is the state of the element in the absence of an activation light. In the embodiment ofFIG. 16A, the piezoelectric elements404,405,406and407are basically flat in the non-activated state. The flat shape of the piezoelectric elements404,405,406and407allows a signal light410to pass through the signal channel402as indicated by the signal light410entering and exiting the signal channel402.

FIG. 16Billustrates the piezoelectric elements404,405,406and407in an activated state that results from the application of an activation light412to the piezoelectric elements404,405,406and407. In the embodiment ofFIG. 16B, the activation light412is applied to the piezoelectric elements404,405,406and407by directing the activation light412into the signal channel402in parallel with the signal light410. The activation light412supplies an electrical field that effects the piezoelectric material. In the activated state, the shape of the piezoelectric elements404,405,406and407changes enough so that the signal light410is blocked from passing through the signal channel402. The blocking of the signal light410is indicated by the lack of the signal light410exiting the signal channel402. Once the activation light412is removed from the signal channel402, the piezoelectric elements404,405,406and407return to normal shape and the signal light410is able once again to pass through the signal channel402.

As described above, activation of the piezoelectric elements404,405,406and407in response to the activation light412causes the shape of the piezoelectric elements404,405,406and407to change, thereby causing at least one dimension of the signal channel402to change.FIG. 17Ais a cross-sectional view of the signal channel402and the piezoelectric element406ofFIG. 16Awhen the piezoelectric element406is in a non-activated state.FIG. 11Bis a cross-sectional view of the signal channel402and the piezoelectric element406ofFIG. 16Bwhen the piezoelectric element406is in an activated state. In the activated state, the piezoelectric element406extends into the signal channel402and reduces at least one dimension of the signal channel402. As illustrated inFIGS. 17A and 17B, the cross-sectional area of the signal channel402is smaller in the activated state (FIG. 17B) than it is in the non-activated state (FIG. 17A).

As seen in the embodiment ofFIGS. 16A-17B, there is still an opening in the signal channel402even when the piezoelectric elements404,405,406and407are in the activated state. Although there is still an opening in the signal channel402even when the piezoelectric elements404,405,406and407are in the activated state, the opening in the signal channel402is small enough that the signal light410is blocked from passing through the signal channel402. The ability of a signal light410to pass through the signal channel402is a function of the dimensions of the signal channel402and of the wavelength of the signal light410. In general, light having a shorter wavelength is able to pass through a signal channel having a smaller dimension than light having a longer wavelength.

Reference is now made toFIG. 18A, which illustrates an optical switch500that includes a signal channel502and a plurality of piezoelectric element which are preferably unevenly spaced along the length of the signal channel502. In the illustrated embodiment three generally oval cylindrical piezoelectric elements504,505and506are distributed along the length of the signal channel502with non-uniform spacing therebetween. The shape of the piezoelectric elements504,505and506is controlled by an activation light. The signal channel502guides the transmission of light within a confined area along a defined path. The signal channel502is formed by a light guiding structure, or combination of structures, which can guide light within a confined area along a defined path. Structures that can form the signal channel include, for example, an optical fiber, substrates such as lithium niobate or other transparent piezoelectric materials that include a signal channel, an optical waveguide, and a chamber for holding a compressible material. In the embodiment ofFIG. 18A, the signal channel502is preferably formed by a monolithic light guiding element.

The piezoelectric elements504,505and506are preferably formed of piezoelectric material. Examples of piezoelectric material that can be used to form the piezoelectric element include crystalline piezoelectric material such as quartz (SiO2), lithium niobate (LiNbO3), lead zirconate (PbZrO3), lead titanate (PbTiO3), and lead zirconate titanate. Examples of piezoelectric materials that can be oriented in a magnetic field are lead zirconate and lead titanate or lead zicronate titantae. Quartz and lithium niobate are examples of transparent piezoelectric materials.

The piezoelectric element504,505and506preferably each include at least two layers507and508of piezoelectric material having different piezoelectric characteristics. The different piezoelectric characteristics of the different layers507and508may include, for example: 1) different degrees of expansion and/or shrinkage in response to the same electrical field; 2) different responses to the same electrical field, for example, one of the layers expands in response to an electrical field having a first orientation and the other layer expands in response to an electrical field having a second orientation that is perpendicular to the first orientation; 3) different polarities; 4) different strains; 5) different hysteresis; 6) different capacitances; 7) different impedances; 8) different resistivities; 9) different thermal histories; and 10) different electromagnetic histories.

The piezoelectric characteristics of a piezoelectric material are a function of, for example: 1) the type of piezoelectric material; 2) the crystal orientation of the piezoelectric material; 3) doping levels within the piezoelectric material; 4) the density of the piezoelectric material; 5) the void density of the piezoelectric material; 6) the chemical constituency of the piezoelectric material; 7) the thermal history of the piezoelectric material; 8) the electromagnetic history of the piezoelectric material. The desired piezoelectric characteristic of each layer of piezoelectric material can be achieved by, for example, manipulating one or more of the above-identified parameters.

Preferably, layers of piezoelectric material that exhibit different degrees of expansion and/or shrinkage in response to the same electrical field are integrated into a piezoelectric element to cause the piezoelectric element to change shape or bend in response to the activation light. For example, if two adjacent layers of a piezoelectric element, which are adhered to each other into a monolithic element, expand different amounts in response to the same activation light, the piezoelectric element will bend. In an embodiment, the piezoelectric element includes at least two layers of piezoelectric material, having different piezoelectric characteristics, which are formed as a monolithic element. For example, the piezoelectric element is formed by building layers of piezoelectric material on top of each other using semiconductor processing techniques, e.g., crystal growth, deposition, sputtering, ion implantation, etc. In an embodiment, the layers of the piezoelectric element have different crystal orientations so that the two layers respond differently to the same electrical field. For example, the two layers have crystal orientations that are perpendicular to each other. In another embodiment, at least one of the layers of the piezoelectric element is made of an organic material.

By using a piezoelectric element with layers of piezoelectric material having different piezoelectric characteristics, the response of the piezoelectric element can be selected to optimize on/off switching. For example, the piezoelectric characteristics of the layers can be selected to: 1) maximize the shape change of the piezoelectric element in response to the activation light; 2) minimize hysteresis; 3) reduce the amount of power required to change the shape of the piezoelectric element; and 4) reduce the amount of heat generated by the switching technique.

Operation of the optical switch500depicted inFIG. 18Ais now described with additional reference toFIG. 18B.FIG. 18Aillustrates the piezoelectric elements504,505and506in a non-activated state. In the non-activated state, the shape of the piezoelectric elements504,505and506is unchanged from its normal state, where the normal state of the piezoelectric elements504,505and506is the state of the element in the absence of an activation light. In the embodiment ofFIG. 18A, the piezoelectric elements504,505and506are basically flat in the non-activated state. The flat shape of the piezoelectric elements504,505and506allows a signal light510to pass through the signal channel502as indicated by the signal light510entering and exiting the signal channel502.

FIG. 18Billustrates the piezoelectric elements504,505and506in an activated state that results from the application of an activation light512to the piezoelectric elements504,505and506. In the embodiment ofFIG. 18B, the activation light512is applied to the piezoelectric elements504,505and506by directing the activation light512into the signal channel502in parallel with the signal light510. The activation light512supplies an electrical field that effects the piezoelectric material. In the activated state, the shape of the piezoelectric elements504,505and506change enough so that the signal light510is blocked from passing through the signal channel502. The blocking of the signal light510is indicated by the lack of the signal light510exiting the signal channel502. Once the activation light512is removed from the signal channel502, the piezoelectric elements504,505and506return to normal shape and the signal light510is able once again to pass through the signal channel502.

As described above, activation of the piezoelectric elements504,505and506in response to the activation light512causes the shape of the piezoelectric elements504,505and506to change, thereby causing at least one dimension of the signal channel502to change.FIG. 19Ais a cross-sectional view of the signal channel502and the piezoelectric element505ofFIG. 18Awhen the piezoelectric element505is in a non-activated state.FIG. 19Bis a cross-sectional view of the signal channel502and the piezoelectric element505ofFIG. 18Bwhen the piezoelectric element505is in an activated state. In the activated state, the piezoelectric element505extends into the signal channel502and reduces at least one dimension of the signal channel502. As illustrated inFIGS. 19A and 19B, the cross-sectional area of the signal channel502is smaller in the activated state (FIG. 19B) than it is in the non-activated state (FIG. 19A).

As seen in the embodiment ofFIGS. 18A-19B, there is still an opening in the signal channel502even when the piezoelectric elements504,505and506are in the activated state. Although there is still an opening in the signal channel502even when the piezoelectric elements504,505and506are in the activated state, the opening in the signal channel502is small enough that the signal light510is blocked from passing through the signal channel502. The ability of a signal light510to pass through the signal channel502is a function of the dimensions of the signal channel502and of the wavelength of the signal light510. In general, light having a shorter wavelength is able to pass through a signal channel having a smaller dimension than light having a longer wavelength.

It is appreciated that all computer logic can be done with three logic gates. These are the AND, OR, and NOR logic gates. These handle digital signals in specific ways that are described using a truth table. The truth table gives the signal that will be output from the gate when specified signals are input into the gate.

Table 1 is a truth table for the logical AND gate. The ones in the A and B input columns indicate that a digital signal pulse is entering the gate. The inputs can come in on the A input or the B input. Only when an input signal is found on both the A input and B input does an output pulse result from the AND gate.

Table 2 is a truth table for the logical OR gate. When an input signal is found on either the A input and B input or both an output pulse results from the OR gate.

Table 3 is a truth table for the logical NOR gate. Only when an input signal is not found on both the A input and B input does an output pulse result from the NOR gate. A NOR gate is often explained as an OR gate with a NOT gate on its output.

The logical NOT gate takes a signal and transforms it into its opposite. When there is a signal coming in, no signal is sent out, and when no signal is coming in, then a signal is sent out.

In present computer circuits, three transistors may be used to make a logical AND or A logical OR gate for electrical digital signals. In present computer circuits, four transistors may be used to make a logical NOR gate. Transistors switch in 10E−9 seconds. This determines how fast a computer can be made to function. Present computers function on the flow of electronic digital signals not light signals. Light signals are also called optical or photonic signals.

The present invention includes AND, OR and NOR logic gates based upon fiber optical switches that are actuated by light and not actuated by an electrical signal or transistor circuit. They require no battery, and if the correct switch is chosen, the gates can be made small enough for semiconductor size constraints. One example of a light activated optical switch is disclosed in U.S. Pat. No. 7,072,536, which incorporated by reference herein. Although one example of a light activated optical switch is identified, the logic gates can be formed using other type of light actuated optical switches.

In an embodiment of the present invention, the light that carries the digital information for the logic is a 1500 nm wavelength signal as in commonly used in present fiber optic channels. This signal can be changed into a 750 nm signal by using a Periodically Poled Lithium Niobate (PPLN) crystal that will double the frequency of the input signal. This frequency doubling makes the wavelength of the signal half of the original wavelength. The change to half of the wavelength is merely an example, as is PPLN. Other wave lengths and means could be used.

With a different configuration PPLN crystals can also produce 1500 nm wavelength light out of 750 nm light. Generally a PPLN element functions only for specific wavelengths and not for others at the same time. During these conversions, power is lost, but optical amplifiers can be used to boost the signal back up to necessary levels. For the present disclosure, the power boosting that is needed, will be included in the frequency doubling function.

Light can be in a fiber optic channel with light that is 180 degrees out of phase, and the electric field of the light will not be expressed. The light that is 180 degrees out of phase with it cancels the power of the light.

Reference is now made toFIG. 20, which is a schematic of a logical NOT gate600for fiber optic systems. InFIG. 20, an optical channel601, such as an optical fiber, brings in a 1500 nm signal that is needed by the logic gate600. An optical channel603, such as an optical fiber, that brings in the 1500 nm signal that will be changed by the logical NOT gate600. A wavelength reducer605doubles the frequency of the incoming signal so that it will be converted to a 750 nm signal, and it has incorporated in it any optical amplification function needed to prepare the signal to be useful after the frequency conversion is accomplished. Optical channel601joins with the output of wavelength reducer605and enters optical switch607. Optical switch607is a light activated optical switch as described above. Optical switch607will allow the 1500 nm signal to be output until a 750 nm signal comes from the wavelength reducer605. When a 750 nm signal comes from wavelength reducer605, no signal is output from optical switch607. Optical channel609provides the output signal from the logical NOT gate600. An output signal is only provided when no signal is input on optical channel603, thus providing a logical NOT gate.

Reference is now made toFIG. 21, which is a schematic of a logical AND gate610. An optical channel611, such as an optical fiber, supplies a higher frequency wave length signal to an optical switch612to actuate switch612. Optical channel611joins with the other fiber optic channels to enter optical switch612after the phase of the light in optical channel611is matched to the light entering a first logical input provided to the logical AND gate610along an optical channel614, by phase matcher616. Optical channel614divides, with half of the light going into a wavelength reducer618, then to phase matcher616and then joins with other optical channels to provide inputs to the optical switch612. The other half of the light in optical channel614is input directly into optical switch612.

A second logical input is provided to the logical AND gate610along an optical channel620. Optical channel620divides, with half of the light going into a wavelength reducer622, then to phase matcher624and then joins with other optical channels to provide inputs to the optical switch612. The other half of the light in optical channel614is input directly into optical switch612.

An optical channel626joins with the other fiber optic channels to provide inputs to optical switch612after the phase of the light in optical channel626is matched to the light of second logical input on optical channel620by phase matcher624. The output of the logical AND gate610is provided along optical channel628, and provides AND functionality as shown in Table 1.

A phase shifter629is provided so that inputs from optical channels614and620will be mutually out of phase by 180 degrees. Thus, optical switch612will open and provide an output signal when light is input along both optical channels614and620and will be closed and no output signal will be provided when light is only input on one of channels614and620. It is appreciated that no output signal will be provided when there is no light input on either of channels614and620.

Thus, the present invention provides a logical AND gate wherein digital signal lights coming into the first and second data inputs are divided into two channels one of which the wavelength is shortened and the phase is matched to switch activation signals. Additionally, a logical AND gate is provided where in the activation light that is phase matched to the shortened wavelength signal that goes into the optical switch and only opens to let a data signal out of the gate when a data signal is received into both inputs thereby satisfying the requirements of a logical AND gate.

Reference is now made toFIG. 22, which is a schematic illustration of a logical AND gate630that uses two light activated optical switches632and634to handle the digital light signal data. A first logical input signal of 1500 nm light is provided to the logical AND gate630along an optical channel636and a second logical input signal of 1500 nm light is provided to the logical AND gate630along an optical channel638. A first optical channel640, such as an optical fiber, supplies an actuation signal of 1500 nm light to optical switch632and a second optical channel642supplies an actuation signal of 1500 nm light to optical switch634.

A first and second wavelength reducer642and646double the frequency of the 1500 nm light so that it becomes 750 nm light. The power is also boosted up to the level needed to activate a light activated optical switch after the frequency is doubled. Optical switches have been designed to activate with an activation light power of 150 milliwatts. One half of the digital light signal output by wavelength reducers642and646along an optical channel647is provided to a light absorber648The other half of the light signal output from wavelength reducers642and646joins with the optical signal input on optical channel640, which is needed to make the logical AND gate630work. Optical switch632will allow the 1500 nm signal on optical channel640to pass through it until a 750 nm signal strong enough to close it is input to an optical channel650. This will occur when a 1500 nm signal comes in to the gate on optical channels636and638. An optical channel652provides the output signal from switch632to a wavelength reducer654. Wavelength reducer654doubles the frequency of the 1500 min signal output by optical switch632along optical channel652.

Optical channel642provides a 1500 nm signal into the logical AND gate630and joins it with the output of wavelength reducer654. Optical switch634will allow the 1500 nm signal from optical channel642to exit the switch as long as no signal is output from optical switch632via wavelength reducer654.

When there is only a signal entering on one of optical channels636and638, the 750 nm signal input into optical switch632is not sufficient to make switch632close and stop the flow of 1500 nm light from optical channel640. When a signal is provided on both optical channels636and638, the signal is sufficient to turn off the 1500 nm signal from optical channel640.

As long as the signal from optical channel640is output from switch632there will be no signal provided from optical switch634.

Only when a 1500 nm signal is provided on both optical channels636and638does the source light from optical channel640get turned off by optical switch632and only then is the input provided by optical channel642output from switch634, thus providing a logical AND gate, with an output of 1500 nm light only when a 1500 nm signal is provided on both optical channels636and638. This logical AND gate operates as in Table 1.

It is appreciated that the change to half of the wavelength is provided merely as an example. Other wave lengths and means could be used.

Thus, the present invention provides a logical AND gate wherein the wavelength of the two input signals are immediately shortened and divided to provide light for the activation of optical switches. Also provided is a logical AND gate wherein light with the wavelength shortened actuates a switch once a data signal enter both inputs of the gate that sends a data wavelength signal that is supplied to a second optical switch. The wavelength of the output signal is increased to be an actuating signal for second optical switch assuring that a data signal only leaves the logical AND gate when two inputs come into the two data ports of the gate there by satisfying the requirements of an logical AND gate.

Reference is now made toFIG. 23, which is a schematic illustration of a logical OR gate700. A first logical input signal of 1500 nm light is provided to the logical OR gate700along an optical channel702and a second logical input signal of 1500 nm light is provided to the logical AND gate700along an optical channel704. An optical channel706provides a source of 750 nm light that feeds an optical switch708. Optical switch708will remain closed and no output 1500 nm signal will be provided unless the 750 nm signal from optical channel706is canceled.

A first and second wavelength reducer710and712double the frequency of the 1500 mm signals provided along optical channels702and704so they become 750 nm signals. An optical amplifier integrated into the device boosts the power lost in the change of the frequency up again to a useful level.

Optical channel714carries the 750 nm signal output from wavelength reducer710to a phase matcher716. The phase matcher716makes the phase of the 750 nm signal from along optical channel714to be in phase with the source signal of 750 nm light along optical channel706.

An optical channel718provides the output from wavelength reducer712to a phase matcher720. The phase matcher720makes the phase of the signal along optical channel718to be in phase with the source signal of 750 nm light along optical channel706.

Optical channels722and724provide half of the light from the phase matchers716and720, respectively, to light absorbers726and728. Phase shifters730are half wave length paths that put the signals from optical channels702and704180 degrees out of phase with the light along optical channel;706that they have been specifically phase matched with. When they mix with the light along optical channel706they will cancel half of it out.

An optical channel732carries the 750 nm source light from phase matcher720, and joins it with the signals from phase shifters730and an optical channel740, which is a source of 1500 nm light that will flow out of switch708until a signal of sufficient power comes from optical channel706to shut it off. The signal is output from switch708along an optical channel742, thus providing a logical OR gate.

As long as the source of 750 nm light from optical channel706is fed into switch708no signal from source of 1500 nm light from optical channel740will be allowed to come out of the logical OR gate, but if a signal comes into either optical channel702or704then the light from optical channel706will be canceled to half power and a 1500 nm signal will be allowed to come out of the logical OR gate.

In addition, if a signal is provided on both optical channels702and704they will be of sufficient power together to totally cancel the source of 750 nm light from optical channel706, resulting in an output signal being provided by the logical OR gate700.

The last paragraph explained how the logical OR gate disclosed herein fulfills the requirements of the logical OR gate truth table seen in Table 2. When a signal is provided along optical channel702or704or both then a 1500 nm signal comes out of the logical OR gate700.

By providing a Logical NOT gate, as described inFIG. 20, on the output of a logical OR gate, described inFIG. 23, a logical NOR gate is made, which will function as the truth table shone in Table 3.

Reference is now made toFIG. 24, which is an alternative logical OR gate800. Lines802and804are optical channels or fibers that provide the optical digital signals A and B coming into the gate. These are 1500 nm light signals. Lines806and807are sources of 1500 nm light for the function of the logical OR gate.

Wavelength reducers808and810are frequency doublers that also boost the power of the light to levels that can activate a light activated optical switch after the frequency is doubled. Line812is a network of optical channels or fibers that carry the signals A and B from wavelength reducers808and810and combine with the signal from line806and carry all this into power limiter814.

Power limiter814allows power levels to pass on that are below a certain maximum. Lines numbered818are optical channels or fibers that carry signals from power limiter814to switch816to wavelength reducer820. Switch816is a light activated optical switch. Wavelength reducer820doubles the frequency of the signal coming out of switch816.

Switch830is a light activated optical switch. Line807is an optical channel or fiber that brings a 1500 nm signal to combine with the output of wavelength reducer820and carry it on to switch830. As long as there is a signal from wavelength reducer820no signal will come out of Switch830.

When a 1500 nm signal enters from Line802(the A signal) it is converted to 750 nm light in reducer808and passes through power limiter814unchanged and turns off the 1500 nm signal from Line806in switch816. So, no signal goes on to turn off the signal from Line807and the OR gate sends out a signal. When a signal comes from Line804(the B signal) passing through reducer810(doubling the frequency), power limiter814to switch816, and no signal from806goes on to turn off switch830. This allows a signal to go from Line807out of the gate through switch830.

If signals come from both Lines802and804, then the double output of the reducers808and810is limited by limiter814to be appropriate for shutting off the signal from line806in switch816. This will allow the signal from Line807to exit the logical OR gate. When a signal comes in to A or B or both then a 1500 nm signal comes out of the logical OR gate. This then functions as truth table in Table 2 proscribes, which describes the function of a logical, OR gate.

A logic gate providing OR functionality and wherein the at least one optical switch includes first and second optical switches and wherein the signal light has a wavelength greater than that of the activation light, the logic gate also including first and second logic inputs receiving signal light inputs, a first wavelength modifier operative to decrease the wavelength of the light along the first light input to the wavelength of the activation light; a second wavelength modifier operative to decrease the wavelength of the light along the second light input to the wavelength of the activation light; first and second light conduits supplying wavelength modified light from the first and second wavelength modifiers; a power limiter receiving light from the first wavelength modifier and second wavelength modifier via the respective first and second light conduits and being operative to maintain light output therefrom at a predetermined power level; a third light conduit supplying power limited light from the power limiter to the first optical switch; a third wavelength modifier receiving signal light from the first optical switch and being operative to decrease the wavelength of the light to the wavelength of the activation light; and a fourth light conduit supplying light from the third wavelength modifier to the second optical switch.

Reference is now made toFIG. 25, which is a schematic of a logical OR gate900. Optical channel902provides a first input to the logical gate900. Optical channel is a fiber optic channel that carries the light signal into the logic gate where it is divided in half. Half of the light is taken to a frequency increasing device numbered905. From frequency increasing device905the light proceeds through a half wave path numbered906that makes the light from905out of phase with the light it will meet from frequency increasing device908. The light from the half wave path906then combines with the light of the logic gate to inter optical switch910. The other half of the light from line902, which is logical input A joins with the other light of the logic gate to enter optical switch910. Line904is input B to the logic gate. Line904is a fiber optic channel that carries the light signal into the logic gate where it is divided in half. Half of the light is taken into a frequency increasing device numbered908. The light from frequency increasing device numbered908then combines with the other light in the logic gate to inter the optical switch numbered910. The other half of the light from line904joins with the other light of the logic device to inter optical switch910. Line912is the output of the logical OR device.

A logic gate providing OR functionality and wherein the at least one optical switch includes a single optical switch and wherein the signal light has a wavelength greater than that of the activation light, the logic gate also including first and second logic inputs receiving signal light, a first light conduit receiving a first portion of the signal light received at the first logic input, a second light conduit receiving a second portion of the signal light received at the first logic input, a third light conduit receiving a first portion of the signal light received at the second logic input, a fourth light conduit receiving a second portion of the signal light received at the second logic input, a first wavelength modifier operative to decrease the wavelength of the light along the second light conduit to the wavelength of the activation light, a second wavelength modifier operative to decrease the wavelength of the light along the fourth light conduit to the wavelength of the activation light and a phase shifter operative to cause wavelength modified light from the first wavelength modifier to be out of phase by 180 degrees with respect to the light from the second wavelength modifier, the optical switch receiving light from the first and third light conduits, the second wavelength modifier and the phase shifter.

A logical NOR gate that functions as the truth table in Table 3 shows is made by putting the logical NOT gate ofFIG. 20on the output of the logical OR gate ofFIG. 24or25. Although some examples of logic gates, which utilize light activated optical switches, are described, other embodiments of AND, OR, NOR and NOT logic gates can be produced using light activated optical switches.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the invention includes both combinations and subcombinations of various features described hereinabove as well as modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not in the prior art.