Method and apparatus for forming optical elements by inducing changes in the index of refraction by utilizing electron beam radiation

The exposure of selected optical materials to large area electron beam irradiation can raise the refractive index of the optical material to allow the fabrication of waveguides, optical fibers, gradient index lenses, interference filters, antireflection coatings, heat reflective thermal control coatings and other optical elements.

This application is related to co-pending U.S. patent application No./“Optical Elements Formed By Inducing Changes In The Index Of Refraction By Utilizing Electron Beam Radiation”/“Method And Apparatus For Forming Optical Elements By Inducing Changes In The Index Of Refraction By Utilizing Electron Beam Radiation”/, filed on the same date as the present application, with the same inventors and commonly assigned to the same assignee as the present invention and herein incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to the optical elements having at least two optical material layers having different refractive indexes and more specifically to optical elements having at least two layers of the same optical material but with different refractive indexes and a method for fabricating optical elements by inducing changes in the index of refraction in optical materials utilizing large area electron beam radiation.

Various optical elements have a multiple layer structure of layers of different optical materials having different indexes of refraction or a multiple layer coating of layers of different optical materials having different indexes of refraction. These multiple layer optical elements have a variety of uses in total internal reflection, wavelength filters and diffraction.

An optical waveguide carries a light beam along a designated path within the waveguide. The optical waveguide is typically formed by utilizing materials of different refractive index. The inner waveguide is formed of a first optical material having a high index of refraction. The outer cladding layer around the inner waveguide is formed of a second different optical material having a second low index of refraction.

The inner waveguide material typically exhibits high optical transmission for a light beam to maximize the internal reflection of a light beam traveling along the inner layer of the waveguide and to minimize the signal loss of the light beam. The current state of the art of producing these waveguides and producing these materials of different index of refraction is to utilize two different materials, which are layered in an additive or subtractive process.

Similarly, the inner cylindrical core layer of an optical fiber will have a high index of refraction while the surrounding cylindrical cladding layer will have a low index of refraction to maximize the internal reflection of a light beam traveling along the inner core of the optical fiber.

An interference filter is formed by a first layer of high refractive index material on a substrate with a second layer of a low refractive index material on the first layer. The interference filter can be an antireflection coating to reduce reflected light by decreasing the refractive index difference between the substrate next to the first layer and the ambient atmosphere next to the second layer. The interference filter can be a heat reflective thermal control film, which transmits visible radiation while reflecting infrared radiation. The interference filter can also be used to reflect or transmit selected wavelengths of light or reflect or transmit ranges of wavelengths of light.

Alternating layers of high and low refractive index materials can be used as diffraction gratings or beamsplitters.

The index of refraction can vary within a layer or across multiple layers to form gradient index optical elements. Optical waveguides and optical fibers can have gradient indexes. A gradient index lens functions by diffraction from the layers of different refractive indexes, rather than the traditional refraction from the curved surface of a lens made from a single material having a single index of refraction.

The two different materials with different indexes of refraction are structurally and/or chemically distinct and are brought together during the assembly process for the optical element.

Typically, these optical elements are fabricated by chemical vapor deposition of the layers of different optical materials. However this limits the possible optical material layers since the layers must be compatible with fabrication by deposition and affinity for bonding with each other. Similarly, the optical materials may require different exposure times, temperatures, pressures and atmospheres which may alter the other optical material.

In waveguides and optical fibers in particular, an optical adhesive may be mandated to bond the layers of structurally and chemically distinct materials together. The adhesive layer will effect waveguiding in waveguides and optical fibers and also effect transmittance and reflectance if used in other optical elements.

The multiple layers of different materials create problems in fabrication as edge breakage and differential polishing rates between the glue and core/cladding materials must be taken into account as well as controlling appropriate glue thickness.

Separate from the fabrication issue is that the dissimilar optical materials may have different coefficients of thermal expansion which will cause the fabricated optical element to function differently or not at all at different temperatures.

It is an object of the present invention to provide different refractive indexes from the same optical material within an optical element.

SUMMARY OF THE INVENTION

According to the present invention, the exposure of selected optical materials to large area electron beam irradiation can raise the refractive index of the optical material to allow the fabrication of waveguides, optical fibers, gradient index lenses, interference filters, antireflection coatings, heat reflective thermal control coatings and other optical elements.

The selected starting optical material is deposited on a substrate. The optical material is then exposed with the electron beam at an energy and dose, while the substrate is heated to the appropriate temperature, to raise the refractive index of the selected optical material on the substrate. The optical material and substrate are preferably loaded into a vacuum chamber with a flood electron source to expose the top side of the substrate and a heating element to apply heat to the back-side of the substrate. The method utilizes a large area electron beam exposure system in a soft vacuum environment. By adjusting the process conditions, such as electron beam total dose and energy, temperature of the selected optical material, and ambient atmosphere, the refractive index of the optical material can be altered to become either a gradient index of refraction or a uniform index of refraction.

The electron beam can partially penetrate the single optical material layer. A single optical material layer can have a first index of refraction. Only the upper portion, or sub-layer, of the single layer is exposed to large beam electron beam radiation. After irradiation, the upper portion of the single layer has a higher index of refraction than the lower portion of the layer, also a sub-layer, which still has the first original index of refraction. The two sub-layers are integral and adjacent to each other. These alternating sub-layers of high and low indexes of refraction can be used as interference filters, an anti-reflection coating for an optical element, a heat reflective thermal control layer for an optical element or a wavelength sensitive reflectance/transmittance interference filter for an optical element. Multiple alternating sub-layers of high and low indexes of refraction can be used as diffraction gratings or beam-splitters.

The use of an aperture mask or an embossing structure controls and limits the electron beam exposure to certain specified areas or sections of the optical material layer. The optical material layer can have a first index of refraction. Only the portion of the optical material layer exposed through the aperture or embossed structure is exposed to the large beam electron beam radiation. After irradiation, the exposed areas or sections of the optical material layer have a higher index of refraction than the remaining unexposed portion of the optical material layer, which still has the first original index of refraction.

High index of refraction areas of the optical material on the low index of refraction optical material layer can form a microlens array, a diffraction grating or a beam-splitter. The high refraction areas of the optical material can form the core layer of a waveguide with the partially or completely surrounding low index of refraction optical material layer forming the cladding layer of the waveguide.

Alternating sections of optical material of high and low indexes of refraction can be used as diffraction gratings or beam-splitters. Layers of optical material of high index of refraction within the optical material layer of low index of refraction can form a binary diffractive optical element.

The electron beam apparatus and method can form an optical fiber for use as a waveguide having a core of a high refractive index surrounded by a cladding layer of a low refractive index formed of the same optical material.

DETAILED DESCRIPTION OF THE INVENTION

The exposure of selected optical materials to electron beam irradiation can convert the existing material into a new state which exhibits more desirable optical and mechanical properties not present in the un-irradiated material. An example of this can be seen inFIGS. 1 and 2which shows a plot of surface refractive index as a function of electron dosage and overall thickness respectively in a uniformly irradiated sample as a function of electron dosage for several amorphous fluoropolymers. The new optical material was created only by exposure to the electron beam. The introduction of extra bonds within, in this case, a high polymer results in a large refractive index change. This conversion can be done selectively in three dimensions in either a continuous or periodic manner in normally non-reactive material systems including oil, waxes, monomers, oligomers, and high polymers such that a number of optically useful devices can be easily fabricated.

Typically, the prior art method of forming a waveguide, optical fiber, gradient index lens, diffraction grating beam-splitter, or interference filter required the use of optical polymers containing photoinitiators, subtractive techniques such as reactive ion etching, or bonding dissimilar materials together with glue layers. In the first case, involving the use of photoinitiators because the wavelength of the radiation typically used to activate the photoinitiator systems creates near-field interference patterns (exhibiting textures on the order of the wavelengths trying to be propagated within the device) scattering losses results. These interference patterns are typically superimposed on the guiding structures used in splitters and other optical devices leading to bridging and striation within the films, all of which result in losses. The inventive use of electron beam processes eliminates interference effects since the equivalent wavelength (of the electron beam) is orders of magnitude less than typical optical exposure tools.

The electron beam imparts sufficient energy to the chemical bonds to create scissions, which leads to the formation of additional networking bonds as these reactive entities recombine within the material. The change in refractive index is due to the process of scission and reformation and (to a lesser extent) due to the extraction of low molecular weight components that are volatilized by the e-beam that are removed by the vacuum system. Due to this dual process, conditions can be created in which the index of refraction can be higher or lower than the index of refraction of the starting material cured using conventional means. This allows a wide range of new materials to be selectively created having improved properties for optical applications.

Examples of the optical starting materials that can be converted using this approach include spin-on glasses, polymers, monomers, oligomers, waxes, and oils. These materials do not outgas significantly in soft vacuum (10-50 millitorr). Other optically useful materials include composites and mixtures including inorganic/organic suspensions, polymers containing organometallics, and sol-gels. Since the formation of bonds does not require an additive such as a photoinitiator, the range of available material blends is large.

Preferred optical materials include the following: Typical spin-on glass materials include methylsiloxane, methylsilsesquioxane, phenylsiloxane, phenylsilsesquioxane, methylphenylsiloxane, methylphenylsilsesquioxane, and silicate polymers. Spin-on glass materials also include hydrogensiloxane polymers of the general formula (H0-1.0SiO1.5-2.0)xand hydrogensilsesquioxane polymers, which have the formula (HSiO1.5)x, where x is greater than about 8. Also included are copolymers of hydrogensilsesquioxane and alkoxyhydridosiloxane or hydroxyhydridosiloxane. Spin-on glass materials additionally include organohydridosiloxane polymers of the general formula (H0-1.0SiO1.5-2.0)n(R0-1.0SiO1.5-2.0)m, and organohydridosilsesquioxane polymers of the general formula (HSiO1.5)n(RSiO1.5)m, where m is greater than 0 and the sum of n and m is greater than about 8 and R is alkyl or aryl.

Typical polymer optical materials include halogenated polyalkylenes, preferred fluorinated an/or chlorinated polyalkylens, more preferred chlorofluoropolyalkylens, and most preferred are the fluorinated polyalkylenes among which are included: polytetrafluoroethane (ethylene), polytrifluoroethylene, polyvinylidene fluoride, polyvinylfluoride, copolymers of fluorinated ethylene or fluorinated vinyl groups with non-fluorinated ethylenesor vinyl groups, and copolymers of fluorinated ethylenes and vinyls with straight or substituted cyclic fluoroethers containing one or more oxygens in the ring. Also included in the most preferred polymers are poly(fluorinated ethers) in which each linear monomer may contain from one to four carbon atoms between the ether oxygens and these carbons may be perfluorinated, monofluorinated, or not fluorinated.

Also included in the most preferred polymer optical materials are copolymers of wholly fluorinated alkylenes with fluorinated ethers, partly fluorinated alkylenes with wholly fluorinated ethers, wholly fluorinated alkylenes with partly fluorinated ethers, partly fluorinated alkylenes with partly fluorinated ethers, non-fluorinated alkylenes with wholly or partly fluorinated ethers, and non-fluorinated ethers with partly or wholly fluorinated alkylenes.

Also included among the most preferred polymer optical materials are copolymers of alkylenes and ethers in which one kind of the monomers is wholly or partly substituted with chlorine and the other monomer is substituted with fluorine atoms. In all the above, the chain terminal groups may be similar to those in the chain itself, or different.

Also among the most preferred polymer optical materials are included substituted polyacrylates, polymethacrylates, polyitaconates, polymaleates, and polyfumarates, and their copolymers, in which their substituted side chains are linear with 2 to 24 carbon atoms, and their carbon atoms are fully fluorinated except for the first one or two carbons near the carboxyl oxygen atom such as Fluoroacrylate, Fluoromethacrylate and Fluoroitaconate.

Among the more preferred polymer optical materials, one includes fluoro-substituted polystyrenes, in which the ring may be substituted by one or more fluorine atoms, or alternatively, the polystyrene backbone is substituted by up to 3 fluorine atoms per monomer. The ring substitution may be on ring carbons No. 4, 3, 2, 5, or 6, preferably on carbons No. 4 or 3. There may be up to 5 fluorine atoms substituting each ring.

Among the more preferred polymer optical materials, one includes aromatic polycarbonates, poly(ester-carbonates), polyamids and poly(esteramides), and their copolymers in which the aromatic groups are substituted directly by up to four fluorine atoms per ring one by one on more mono or trifluoromethyl groups such as shown inFIGS. 3A,3B,3C,3D and3E.

Among the more preferred polymer optical materials, are fluoro-substituted poly(amic acids) and their corresponding polyimides, which are obtained by dehydration and ring closure of the precursor poly(amic acids). The fluorine substitution is effected directly on the aromatic ring. Fluoro-substituted copolymers containing fluoro-substituted imide residues together with amide and/or ester residues are included.

Also among the more preferred polymer optical materials are parylenes, fluorinated and non-fluorinated poly(arylene ethers), for example the poly(arylene ether) available under the tradename FLARE™ from AlliedSignal Inc., and the polymeric material obtained from phenyl-ethynylated aromatic monomers and oligomers provided by Dow Chemical Company under the tradename SiLK™, among other materials.

In all the above, the copolymers may be random or block or mixtures thereof.

The method of creating optical materials with changed refractive indexes from these conventional spin-on glass and polymer materials, according to the present invention, is depicted inFIGS. 4 and 5. A substrate127is placed in a vacuum chamber120at a pressure of 15 to 40 millitorr and underneath an electron source at a distance from the source sufficient for the electrons to generate ions in their transit between the source and the substrate surface. The electrons can be generated from any type of source that will work within a soft vacuum (15 to 40 milliTorr) environment. A source particularly well suited for this is described in U.S. Pat. No. 5,003,178, the disclosure of which is hereby incorporated into this specification by reference. This is a large uniform and stable source that can operate in a soft vacuum environment. The cathode122emits electrons. The electrons are accelerated by the field between the cathode and anode126. The potential between these two electrodes is generated by the high voltage supply129applied to the cathode122and the bias voltage supply130applied to the anode126. The electrons irradiate the starting optical material layer128coated on the substrate127. The starting optical material layer128may be any of the materials previously mentioned or the spin-on glass or polymer materials described above. An electron energy is selected to either fully penetrate or partially penetrate the full thickness of starting optical material layer128. For example, a large area electron beam energy of 9 keV is used to penetrate a 6000 Angstrom thick film. Infrared quartz lamps136irradiate the bottom side of the substrate providing heating independent from the electron beam. A variable leak valve or mass flow controller, identified by reference132, is utilized to leak in a suitable gas to maintain the soft vacuum environment.

Referring toFIG. 5, electrons145traversing the distance146between the anode126and the substrate127ionize the gas molecules located in region138generating positive ions. These positive ions143are then attracted back to the anode126where they can be accelerated, as indicated at142, toward the cathode to generate more electrons. The starting optical material layer128on the substrate127is an insulator and will begin to charge negatively, as indicated at147, under electron bombardment. However, the positive ions near the substrate surface will be attracted to this negative charge and will then neutralize it. The lamps136(FIG. 4) irradiate and heat the starting optical material layer or substrate thereby controlling its temperature. Since the starting optical material layer is in a vacuum environment and thermally isolated, the starting optical material layer can be heated or cooled by radiation. If the lamps are extinguished, the starting optical material layer will radiate away its heat to the surrounding surfaces and gently cool. In one embodiment of the invention, the starting optical material layer is simultaneously heated by the infrared lamps and irradiated by the electron beam throughout the entire process.

In the present method, a solution containing a spin-on glass or polymer material is deposited on substrate127by conventional means such as spin-coating or, alternatively, spray-coating or dip-coating to form starting optical material layer128. Substrate127represents any layer or stack of layers on a multiple-optical layer device. The coated substrate is continuously irradiated with electrons until a sufficient dose has accumulated to attain the desired change in the material and affect starting optical material layer properties such as refractive index. A total dose of between 10 and 100,000 microCoulombs per square centimeter (μC/cm2) may be used. Preferably, a dose of between 100 and 10,000 μC/cm2is used, and most preferably a dose of between about 2,000 and 5,000 μC/cm2is used. The electron beam is delivered at an energy of between 0.1 and 100 keV, preferably at an energy between 0.5 and 20 keV, and most preferably at an energy between 1 and 10 keV. The electron beam current ranges between 0.1 and 100 mA, and more preferably between 0.25 and 30 mA. The entire electron dose may be delivered at a single voltage. Alternatively, particularly for starting optical material layers thicker than about 0.25 μm, the dose is divided into steps of decreasing voltage, which provides a “uniform dose” process in which the material is irradiated from the bottom up. The higher energy electrons penetrate deeper into the starting optical material layer. In this way, the depth of electron beam penetration is varied during the electron exposure process resulting in a uniform energy distribution throughout the starting optical material layer. The variation allows for volatile components, such as solvent residues, to leave the starting optical material layer without causing any damage such as pinholes or cracks. This also attains uniform refractive index throughout the layer exposed. Alternatively, the electron energy can be varied to achieve a precise dose and refractive index change spatially within the material.

During the electron beam exposure process, the starting optical material layer is kept at a temperature between 10 degrees Celsius and 1000 degrees Celsius. Preferably, the wafer temperature is between 30 degrees Celsius and 500 degrees Celsius. For some waxes and other low melting point materials low temperatures are utilized (25 degrees to 175 degrees Celsius). The infrared quartz lamps36are on continuously until the starting optical material layer temperature reaches the desired process temperature. The lamps are turned off and on at varying duty cycle to control the starting optical material layer temperature. Typical background process gases in the soft vacuum environment include nitrogen, argon, oxygen, ammonia, forming gas, helium, methane, hydrogen, silane, and mixtures thereof. For many starting optical materials, a non-oxidizing processing atmosphere is used. For other applications, an oxidizing atmosphere would be appropriate. The optimal choice of electron beam dose, energy, current, processing temperature, and process gas depends on the composition of the starting optical material, spin-on glasses or polymer material.

The optical starting material may be deposited onto a suitable substrate. Typical substrates include glass, silicon, metal, and polymer films. Substrates can also be porous, textured or embossed. Deposition on substrates may be conducted via conventional spin coating, dip coating, roller coating, spraying, embossing, chemical vapor deposition methods, or meniscus coating methods, which are well known in the art. Spin coating on substrates is most preferred. Multiple layers of the same optical materials are also preferred. Layer thicknesses typically range from 0.01 to 20 microns. 1 to 10 microns is preferred. In another embodiment of the invention, the optical starting material is formed into a supported film similar to pellicles used in semiconductor applications. In this case, starting optical material layers may be formed by casting, spin coating, and dip coating, lifted off the substrate and attached to a frame for handling. In addition, extruded starting optical material layers can be attached to a frame, all of which are well known in the art. Casting, with lift-off and frame attachment is preferred. Single starting optical material layers exhibit thicknesses ranging from 1 micron to 10 microns. Once the article has been formed, the exposure equipment needs to be selected.

Exposure of the starting optical material layer can be done with any type of low energy electron source, preferably in the range of 1 to 50 keV. Soft vacuum (15 to 40 milliTorr) is also preferred for removal of volatiles and usage of low keV electrons. In the preferred embodiment of this invention, the starting optical material, either on a substrate or as supported film, is selectively exposed to the electron beam and heated using the IR lamps. Selective heating is also preferred. The IR lamps typically operate from room temperature to 400 degrees Celsius. Most optical materials exhibit different e-beam irradiation responses depending on the temperature of the material. In-situ monitoring of the exposure process is included in this invention such as monitoring grating spectral response concerning side lobes during exposure. Other functions such as transmission loss, polarization sensitivity, and back reflections can all be monitored during exposure and used in a feedback loop to the exposure parameters. In-situ feedback during exposure is an embodiment of this invention. Various gases can be introduced during the irradiation process. It has been shown that these gases can be reacted into the starting optical material layer depending on the material and exposure conditions. Introduction of a reactive or non-reactive gas into the starting optical material layer during exposure is a further embodiment of this invention. Radial exposure conditions, as well as other non-flat configurations, are embodiments of this invention as well as modification of the electron field using external means such as magnetic fields. Once the equipment is selected, the exposure conditions are selected.

Typically the starting optical material layer is exposed to a sequential series of kinetic energies generating a particular distribution of bond densities within the optically useful material. Based on the optical material's particular e-beam response, temperature distribution within the material, kinetic energy distribution of the electrons, and density of the material, a range of refractive index changes can be generated. Preferred starting optical material layer change includes 3 dimensional complex index of refraction. Exposure can be done through an aperture mask as known in the art or by embossing or forming an absorptive mask directly on the starting optical material layer or on a thin carrier film support above the starting optical material layer. In the case of starting optical material layers, dual sided processing can be used. The mask can be either sacrificial or permanent depending on the application. In this embodiment of the invention, rather than forming a binary system a gradient of exposure can be generated.

As shown inFIG. 6, a variety of starting optical material layer structures can be formed using embossing or photolithography steps known in the art. During exposure the areas covered by the mask would proportionally absorb electrons as a function of the embossed thickness. As stated earlier, both the dosage and energy distribution is affected by this approach. But it has been demonstrated that a variety of gradient structures can be generated using this patterning technique and a number of the examples include this approach. In addition, because the starting optical material layer or a thin membrane supports the mask, multiple sequential masks are not required. In the case of embossed or textured starting materials, the need for a mask can be totally eliminated. The embossed structure is irradiated such that the penetration depth is less than feature height. The result is a region of higher refractive index on pedestal after overcoating the resulting waveguide structure appears. In addition, a waveguide can be created on a grating surface. Because the irradiation condition determines the penetration depth, the resulting waveguide will follow the rapid modulation in the grating. Multiple layered configurations are also embodiments of this invention and will be shown in some of the following examples as will the use of this technique to couple closely spaced waveguides and other optical devices. A further embodiment involves the use of the proximity effect to directly form tapered waveguides. Due to spreading as a function a depth that occurs, an array of micro-optical waveguides can be formed in a film. Once the sample is exposed, fabrication into a device can commence.

The electron beam apparatus and method can be used to change the refractive index for an entire layer of optical material.

As shown inFIG. 7A, the substrate200has an upper surface202and a lower surface204. The starting optical material layer206has an upper surface208and a lower surface210. The lower surface210of the starting optical material layer is deposited, bonded, coated, or otherwise positioned on the upper surface202of the substrate. The starting optical material layer206will have an original index of refraction n0.

As shown inFIG. 7B, a large area electron beam212is incident at a perpendicular angle to the upper surface208of the optical material layer206and irradiates the optical material layer. Infrared radiation beams214will heat the substrate200through the lower surface204and, by heat transfer through the substrate, will heat the starting optical material206. The electron beam212fully penetrates the depth or thickness218of the optical material layer to the lower surface210of the optical material layer206and the upper surface202of the substrate200.

As shown inFIG. 7C, the entire optical material layer206, after electron beam irradiation and heating, will have a uniform index of refraction n1, which is higher than the original index of refraction n0of the starting optical material layer, through the full thickness218of the optical material layer.

Alternately, the electron beam irradiation can form a gradient index of refraction from n0.1to n1within the optical material layer206. The index of refraction will increase from the lower surface210to the upper surface208. The temperature of the substrate supporting the starting optical material, the voltage of the electron beam, the dose of the electron beam, the duration and number of steps of the electron beam, the use of oxidizing or non-oxidizing gases in the low vacuum atmosphere, can each separately, or in combination, be varied to fabricate a gradient index of refraction within the starting optical material.

The optical material layer can be removed from the substrate by conventional chemical, etching or physical means. Alternately, a release layer (not shown in this Figure) can be deposited on the substrate and the starting optical material layer can be deposited on the release layer. The electron beam radiation and heat radiation will pass through the release layer without effecting the release layer or the transformation of the starting optical material layer. After the transformation process, the optical material layer can be lifted off the substrate by dissolving the release layer.

The electron beam apparatus and method can provide a layer of one refractive index integral and adjacent to a layer of another refractive index with both layers formed of the same optical material.

As shown inFIG. 8A, the substrate300has an upper surface302and a lower surface304. The starting optical material layer306has an upper surface308and a lower surface310. The lower surface310of the starting optical material layer is deposited, bonded, coated, or otherwise positioned on the upper surface302of the substrate. The starting optical material layer306will have an original index of refraction n0and a thickness312.

As shown inFIG. 8B, a large area electron beam314is incident at a perpendicular angle to the upper surface308of the optical material layer306and irradiates the optical material layer. Infrared radiation beams316will heat the substrate300through the lower surface304and, by heat transfer through the substrate, will heat the starting optical material306. The electron beam314partially penetrates the optical material layer to a depth or thickness318from the upper surface308between the upper surface308and the lower surface310of the optical material layer. The penetration depth318is less than the thickness312of the optical material layer.

As shown inFIG. 8C, the partial penetration of the electron beam irradiation divides the optical material into a first sub-layer and a second sub-layer. The optical material layer306has a second or upper sub-layer320having an upper surface308and a lower surface322and a first or lower sub-layer324having an upper surface326and a lower surface310. The lower surface322of the upper sub-layer is on the upper surface326of the lower sub-layer. The lower surface310of the lower sub-layer is on the upper surface302of the substrate. Since the starting optical material layer is one layer, after electron beam irradiation, the second sub-layer is integral and positioned adjacent and on top of the first sub-layer within the optical material layer.

The second or upper optical material sub-layer320will have an index of refraction n1, which is higher than the original index of refraction n0of the starting optical material layer306. The lower surface322of the upper sub-layer is at the irradiation penetration depth318of the electron beam. The upper sub-layer will have a thickness equivalent to the penetration depth of the electron beam.

The first or lower optical material sub-layer324, which was not irradiated by the electron beam, has the original index of refraction n0of the starting optical material306. The lower sub-layer will have a thickness328equivalent to the original thickness312of the starting optical material less the thickness318of the upper sub-layer.

The optical material layer will have a second sub-layer with a high refractive index on top of a first sub-layer with a lower refractive index without fabrication by deposition, without an intervening adhesive layer between the two sub-layers, and with both sub-layers being formed from the same optical material.

The depth of the penetrating electron beam and the resulting thickness of the altered refractive index layer are determined by the dose, voltage and duration of the electron beam and accordingly can vary from the upper surface of the starting optical material layer to the lower surface of the starting optical material layer.

The second or upper sub-layer320can alternately have a gradient index of refraction. The temperature of the substrate supporting the starting optical material, the voltage of the electron beam, the dose of the electron beam, the duration and number of steps of the electron beam, the use of oxidizing or non-oxidizing gases in the low vacuum atmosphere, can each separately, or in combination, be varied to fabricate a gradient index of refraction within the starting optical material.

As shown inFIG. 8D, the optical material layer306can be removed from the substrate by conventional chemical, etching or physical means. Alternately, a release layer (not shown in this Figure) can be deposited on the substrate and the starting optical material layer can be deposited on the release layer. The electron beam radiation and heat radiation will pass through the release layer without effecting the release layer or the transformation of the starting optical material layer. After the transformation process, the optical material layer can be lifted off the substrate by dissolving the release layer.

The optical material layer306will be inverted and deposited, bonded or positioned on the surface350of an optical element352. The upper surface308of the second sub-layer will be attached to the upper surface350of the optical element. The lower surface310of the first sub-layer will be the outer surface of then optical material on the optical element. The second sub-layer324is adjacent to the optical element350with the first sub-layer320being on the outside.

The sequence will be optical element350, the second sub-layer320with a high refractive index and the first sub-layer324with a low refractive index. If the optical thickness318of the second sub-layer320and the optical thickness328of the first sub-layer324are in quarter-wavelengths or whole number multiples of quarter wavelengths for the light transmitted through or reflected from the optical element, the two sub-layers of the optical material will form an interference filter which can be an anti-reflection coating for the optical element or a heat reflective thermal control layer for the optical element or a wavelength sensitive reflectance/transmittance interference filter for the optical element352.

An interference filter is formed by a high refractive index material layer on a substrate with a low refractive index material layer on the high refractive index material layer. The antireflection coating reduces reflected light by decreasing the refractive index difference between the optical element next to the adjacent high refractive layer and the ambient atmosphere next to the low refractive index layer. The heat reflective thermal control film transmits visible radiation while reflecting infrared radiation. The wavelength sensitive reflectance/transmittance interference filter can reflect or transmit selected wavelengths of light or reflect or transmit ranges of wavelengths of light.

The electron beam apparatus and method of the present invention allows the thickness of the low refractive sub-layer of the optical material and the thickness of the high refractive sub-layer of the same optical material to be individually selected for use in an optical element. The thicknesses can be fractions of wavelengths or ratios to each other.

As shown inFIG. 9A, a first starting optical material layer400is bonded, deposited, coated or positioned on a substrate402. A large area electron beam (not shown) irradiates the first starting optical material layer while infrared beams (also not shown) heat the substrate and first starting optical material layer. The first optical material layer400will form a low refractive index sub-layer404and a high refractive index sub-layer406.

A second starting optical material layer408is bonded, deposited, coated or positioned on the high refractive index sub-layer406of the first starting optical material layer400. A large area electron beam (not shown) irradiates the second starting optical material layer while infrared beams (also not shown) heat the second starting optical material layer. The second optical material layer408will form a low refractive index sub-layer410and a high refractive index sub-layer412.

As shown inFIG. 9B, the first and second starting optical material layers400and408with the sub-layers can be removed from the substrate by the use of a release layer or by conventional chemical, etching or physical means and inverted to form an optical element414.

The resulting optical element414has alternating layers of high and low refractive index materials. The optical element can have multiple optical material layers with multiple alternating layers of high and low refractive index materials formed by the electron beam apparatus and method of the present invention.

The starting optical material layers for the optical element can be the same with the low refractive sub-layers sharing the same original index of refraction. The high refractive sub-layers can have the same or different indexes of refraction. The electron beam apparatus and method can form different indexes of refraction for the same optical material based on the temperature of the substrate supporting the starting optical material, the voltage of the electron beam, the dose of the electron beam, the duration and number of steps of the electron beam, and the use of oxidizing or non-oxidizing gases in the low vacuum atmosphere.

As noted earlier, the thicknesses of the layers of high and low refractive index materials can be individually selected for each sub-layer in the optical element. The optical element can have layers of the original starting optical material without its refractive index changed and solid layers (without sub-layers) of optical material with a raised refractive index like the optical material206ofFIG. 7.

The starting optical material layers in the optical element can be different optical materials providing different refractive indexes for the alternating layer of high and low refractive index materials.

The optical element of multiple optical material layers with multiple alternating layers of high and low refractive index materials, with a range of refractive indexes and thicknesses and optical materials, can be used as a conventional diffraction grating, a conventional interference filter, or a conventional beam-splitter, as is known in the art.

The optical element of multiple optical material layers with multiple alternating layers of high and low refractive index materials can be used as an interference filter, which can be an anti-reflection coating or a heat reflective thermal control layer or a wavelength sensitive reflectance/transmittance interference filter.

The temperature of the substrate supporting the starting optical material, the voltage of the electron beam, the dose of the electron beam, the duration and number of steps of the electron beam, the use of oxidizing or non-oxidizing gases in the low vacuum atmosphere, can each separately, or in combination, be varied to fabricate a gradient index of refraction within the optical material.

The electron beam apparatus and method can provide adjacent integral multiple layers of different increasing refractive indexes with the multiple layers formed of the same optical material.

As shown inFIG. 10A, the substrate500has an upper surface502and a lower surface504. The starting optical material layer506has an upper surface508and a lower surface510. The lower surface510of the starting optical material layer is deposited, bonded, coated, or otherwise positioned on the upper surface502of the substrate. The starting optical material layer506will have an original index of refraction n0and a thickness512.

As shown inFIG. 10B, a first large area electron beam514is incident at a perpendicular angle to the upper surface508of the optical material layer506and irradiates the optical material layer. Infrared radiation beams516will heat the substrate500through the lower surface504and, by heat transfer through the substrate, will heat the starting optical material506. The first electron beam514partially penetrates the optical material layer to a depth or first thickness518from the upper surface508between the upper surface508and the lower surface510of the optical material layer. The first penetration depth518is less than the thickness512of the optical material layer.

As shown inFIG. 10C, the partial penetration of the electron beam irradiation divides the optical material into a first sub-layer and a transitional sub-layer. The optical material layer506has a transitional or upper sub-layer520having an upper surface508and a lower surface522and a first or lower sub-layer524having an upper surface526and a lower surface510. The lower surface522of the transitional sub-layer is on the upper surface526of the lower sub-layer. The lower surface510of the lower sub-layer is on the upper surface502of the substrate.

The transitional sub-layer520will have an index of refraction n1, which is higher than the original index of refraction of the starting optical material layer506. The lower surface522of the transitional sub-layer is at the first irradiation penetration depth518of the electron beam. The first sub-layer524, which was not irradiated by the electron beam, has the original index of refraction n0of the starting optical material506.

As shown inFIG. 10D, a second large area electron beam528is incident at a perpendicular angle to the upper surface508of the transitional sub-layer520and irradiates the optical material in the transitional sub-layer. Infrared radiation beams530will heat the substrate500through the lower surface504and, by heat transfer through the substrate500and the first sub-layer524, will heat the transitional sub-layer520.

The second electron beam528partially penetrates the optical material of the transitional sub-layer layer520to a depth or second thickness532from the upper surface508between the upper surface508of the transitional sub-layer526and the upper surface of the first sub-layer524. The second irradiation penetration depth532is less than the thickness of the optical material512and is less than the first irradiation penetration depth518. The second electron beam528does not penetrate the first sub-layer524, only partially penetrating the transitional sub-layer520.

As shown inFIG. 10E, the partial penetration of the second electron beam irradiation divides the transitional sub-layer of optical material into a second sub-layer and a third sub-layer. The optical material will have a third or upper sub-layer534having an upper surface508and a lower surface536and a second or middle sub-layer538having an upper surface540and a lower surface522. The lower surface536of the third sub-layer534is on the upper surface540of the second sub-layer538. The lower surface522of the second sub-layer538is on the upper surface526of the first sub-layer524.

Since the starting optical material layer is one layer, after electron beam irradiation, the third, second and first sub-layer are integral with third sub-layer positioned adjacent to and on top of the second sub-layer and the second sub-layer positioned adjacent to and on top of the first sub-layer within the optical material layer.

The third sub-layer534will have an index of refraction n2, which is higher than the index of refraction n1of the second sub-layer538, and higher than the index of refraction n0of the first sub-layer524and the starting optical material layer506. The lower surface536of the third sub-layer534is at the second irradiation penetration depth518of the electron beam. The third sub-layer534has been exposed to the first and second electron beam. The second sub-layer538has only been exposed to the first electron beam. The first sub-layer524, which was not irradiated by the second electron beam nor the first electron beam, has the original index of refraction n0of the starting optical material506.

The third sub-layer534will have a thickness equivalent to the second penetration depth532of the second electron beam. The second sub-layer538will have a thickness equivalent to the first penetration depth518of the first electron beam less the second penetration depth532of the second electron beam. The first sub-layer524will have a thickness equivalent to the original thickness512of the starting optical material less the thickness of the second and third sub-layers (or equivalent to the original thickness of the starting optical material512less the thickness of the first penetration depth518).

The optical material506has a first or lower sub-layer524with a first index of refraction, a second or middle sub-layer538with a second index of refraction higher than the first index of refraction and a third or upper sub-layer534with a third index of refraction higher than the second index of refraction and higher than the first index of refraction.

The optical material layer506has sub-layers of progressively higher indexes of refraction without fabrication by deposition, without an intervening adhesive layer between the layers, and with all the layers being formed from the same material.

The optical material layer506can be removed from the substrate by conventional chemical, etching, physical means or the use of a release layer, as discussed previously. After release, the optical material layer can be inverted. The inverted optical material layer506has sub-layers of progressively lower indexes of refraction without fabrication by deposition, without an intervening adhesive layer between the layers, and with all the layers being formed from the same material.

The optical material layer506can be used as an interference filter, as discussed previously or formed into multiple alternating layers to be used as a diffraction grating or beam-splitter, also as discussed previously.

The temperature of the substrate supporting the starting optical material, the voltage of the electron beam, the dose of the electron beam, the duration and number of steps of the electron beam, the use of oxidizing or non-oxidizing gases in the low vacuum atmosphere, can each separately, or in combination, be varied to fabricate a gradient index of refraction within the starting optical material.

Alternately, the multiple electron beam irradiation can form multiple sub-layers of increasing uniform or gradient indexes of refraction with each sub-layer having an index of refraction greater than the original index of refraction n0of the starting optical material. There would be no sub-layers of just the original starting optical material. Every sub-layer would be irradiated with electron beams to increase its index of refraction.

As shown inFIG. 11A, the substrate600has an upper surface602and a lower surface604. The starting optical material layer606has an upper surface608and a lower surface610. The lower surface610of the starting optical material layer is deposited, bonded, coated, or otherwise positioned on the upper surface602of the substrate. The starting optical material layer606will have an original index of refraction n0.

As shown inFIG. 11B, a large area electron beam612is incident at a perpendicular angle to the upper surface608of the optical material layer606and irradiates the optical material layer. Infrared radiation beams614will heat the substrate600through the lower surface604and, by heat transfer through the substrate, will heat the starting optical material606. The electron beam612fully penetrates the depth or thickness618of the optical material layer to the lower surface610of the optical material layer606and the upper surface602of the substrate600.

The electron beam provides precisely controlled electron doses at selected energies at differing relative depths causing an unequal distribution of electron energy along the depth of the starting optical material which results in varying indexes of refraction along the depth of the material.

As shown inFIG. 11C, the entire optical material layer606, after electron beam irradiation and heating, will have a gradient index of refraction which varies from n1to n2by depth, with the upper refractive index n2closer to the upper surface being higher than the lower refractive index n1closer to the lower surface. Both refractive indexes n1to n2are higher than the original index of refraction n0, through the full depth618of the optical material layer.

The refractive index of the optical material606ofFIG. 8can vary by progressions other than straight line gradient, such as exponential or logarithmic, which are illustrative examples but not an exhaustive list of examples.

An embossing structure can be used with the electron beam apparatus and method to pattern the refractive index areas within the same optical material layer.

As shown inFIG. 12A, the substrate700is a support ring with an upper surface702and a lower surface704. The starting optical material layer706has an upper surface708and a lower surface710. A small portion712of the lower surface710of the starting optical material layer is deposited, bonded, coated, or otherwise positioned on the upper surface202of the substrate support ring. A large portion714of the lower surface710of the starting optical material layer remains exposed. The support ring can substitute for a substrate layer in this and other embodiments of the present invention. The starting optical material layer706will have an original index of refraction n0and a thickness716.

As shown inFIG. 12B, an embossed structure718is formed of photoresist and has a series of concave surfaces720on its upper surface722. The lower surface724of the embossed structure718is flat and deposited or positioned on the upper surface708of the starting optical material706.

A large area electron beam726is incident at a perpendicular angle to the upper surface722of the embossed structure718and irradiates the embossed structure718and the optical material layer706. Infrared radiation beams728will heat the starting optical material706through the exposed portion714of the lower surface710of the starting optical material layer706.

The electron beam726fully penetrates the embossed structure718and partially penetrates the starting optical material layer706between the between the upper surface708and the lower surface710of the optical material layer.

As shown inFIG. 12C, the embossing structure718of photoresist is removed by conventional means. The optical material layer706is removed from the substrate support rings700by conventional chemical, etching, physical means or the use of a release layer, as discussed previously.

The partial penetration of the electron beam irradiation forms semi-circular concave areas730having a varying thickness732from the upper surface708extending into the optical material706. These areas730will have an index of refraction of either n2to n1or n1, which is higher than the original index of refraction n0of the starting optical material layer706. The lower surface734of the areas is at the irradiation penetration depth of the electron beam through the embossing structure and into the optical material layer. The varying thickness of the areas is in inverse proportion to the upper surface of the embossed structure.

The surrounding optical material sub-layer706, which was not irradiated by the electron beam, has the original index of refraction n0of the starting optical material layer. The lower sub-layer will have a thickness736equivalent to the original thickness716of the starting optical material less the thickness732of the areas730.

Since the starting optical material layer is one layer, after electron beam irradiation, the areas730of high refractive index are integral and positioned adjacent to the surrounding optical material sub-layer706within the optical material layer.

The areas730of high refractive index form a microlens structure in the optical material layer706. The microlens structure is in inverse image of the embossing structure.

The optical material layer with a lower refractive index will have a microlens structure with a high refractive index without fabrication by deposition, without an intervening adhesive layer between the structure and layer, and with both structure and layer being formed from the same optical material.

The depth of the penetrating electron beam and the resulting thickness of the altered refractive index layer are determined by the dose, voltage and duration of the electron beam and accordingly can vary from the upper surface of the starting optical material layer to the lower surface of the microlens structure.

The electron beam can provide a uniform refractive index n1to the resulting irradiated optical material of the microlens structure, as discussed inFIG. 8, to form a binary diffractive lens. Or the electron beam can provide a gradient refractive index n2to n1to the resulting irradiated optical material of the microlens structure, as discussed inFIG. 11, to form a gradient index (GRIN) lens. The gradient refractive index lens will have a refractive index which varies from n1to n2by depth, with the upper refractive index n2closer to the upper surface of the optical material being higher than the lower refractive index n1closer to the lower surface of the optical material. Both refractive indexes n1to n2are higher than the original index of refraction n0, of the starting optical material layer. The GRIN array and the optical material layer can be lifted off the substrate by dissolving the release layer.

As shown in an alternate embossed structure embodiment ofFIG. 13A, a wax embossed structure800of 120 degree included angle prisms802at a regular pitch interval is deposited on the upper surface804of the starting optical material806. The starting optical material806is positioned on a substrate support ring808. The electron beam apparatus and method are the same as inFIG. 9.

A large area electron beam810is incident at a perpendicular angle to the upper surface812of the embossed structure800and irradiates the embossed structure800and the optical material layer806. Infrared radiation beams814will heat the starting optical material806through the exposed portion816of the lower surface818of the starting optical material layer806.

The electron beam810fully penetrates the embossed structure800and partially penetrates the starting optical material layer806between the between the upper surface804and the lower surface818of the optical material layer.

As shown inFIG. 13B, the embossing structure800of wax is removed by conventional means. The optical material layer806is removed from the substrate support rings808by conventional chemical, etching, physical means or the use of a release layer, as discussed previously.

The partial penetration of the electron beam irradiation forms a refractive index gradient patterned area820, triangular in cross-section, from the upper surface804extending into the optical material806. These triangular areas820will have a varying refractive index from n1to n2by depth, with the upper refractive index n2closer to the upper surface804being higher than the lower refractive index n1closer to the lower surface818. Both refractive indexes n1to n2are higher than the original index of refraction n0. The lower surface822of the triangular areas is at the irradiation penetration depth of the electron beam through the embossing structure and into the optical material layer. The varying thickness of the areas is in inverse proportion to the upper surface812of the embossed structure. The index gradient is in inverse image of the embossing structure.

The surrounding optical material sub-layer806, which was not irradiated by the electron beam, has the original index of refraction n0of the starting optical material layer.

Since the starting optical material layer is one layer, after electron beam irradiation, the areas820of high refractive index are integral and positioned adjacent to the surrounding optical material sub-layer806within the optical material layer.

The index gradient820can be used as a diffraction grating or a beam-splitter. Light propagating within the alternating sections of low and varying high refractive index in the resulting optical material layer will be extracted by the index gradient.

The electron beam can provide a uniform refractive index n1to the resulting irradiated optical material of the index gradient structure, as discussed inFIG. 11, to form a refractive lens.

An aperture mask can be used with the electron beam apparatus and method to provide a section of one refractive index integral and adjacent to a section of another refractive index with both sections formed of the same optical material.

As shown inFIG. 14A, the substrate900has an upper surface902and a lower surface904. The starting optical material layer906has an upper surface908and a lower surface910. The lower surface910of the starting optical material layer is deposited, bonded, coated, or otherwise positioned on the upper surface902of the substrate. The starting optical material layer906will have an original index of refraction n0and a thickness912.

As shown inFIG. 14B, an aperture mask914is positioned between the electron beam source (not shown in this Figure) and the starting optical material layer906. The mask914has an upper surface916and apertures918.

A large area electron beam920is incident at a perpendicular angle to the upper surface908of the optical material layer906through the apertures918of the mask914and irradiates the optical material layer through the mask apertures918. The electron beam920will be absorbed, or otherwise blocked, by the surface916of the mask914but will be transmitted through the apertures918. Infrared radiation beams922will heat the substrate900through the lower surface904and, by heat transfer through the substrate, will heat the starting optical material906.

The electron beam920fully penetrates the depth or thickness912of the optical material layer906to the lower surface910of the optical material layer906and the upper surface902of the substrate900in the first sections922of the optical material layer906exposed to the electron beam through the apertures918. Second sections924of the optical material layer906was not exposed to the electron beam920because the mask914absorbed or blocked the electron beam.

As shown inFIG. 14C, the aperture mask914is removed. The optical material layer906is removed from the substrate900by conventional chemical, etching, physical means or the use of a release layer, as discussed previously.

After heating and electron beam irradiation through the mask aperture, the first section922of the optical material layer906will have an index of refraction n1, which is higher than the original index of refraction n0of the starting optical material layer, through the full thickness912of the optical material layer. The second section924of the optical material layer906, which was not exposed to the electron beam irradiation, will have the original index of refraction n0of the starting optical material layer. Since the starting optical material layer is one layer, after electron beam irradiation, the first section is integral and positioned adjacent to the second section within the optical material layer.

The mask serves to restrict the electron beam spatially limiting its irradiation to the apertured sections of the optical material layer.

The optical material layer will have adjacent sections of different refractive indexes but formed from the same optical material and can be used as a diffraction grating or interference filter.

The optical material layer will have adjacent sections of different refractive indexes without fabrication by deposition, without an intervening adhesive layer between the structure and layer or between adjacent sections, and with both adjacent sections being formed from the same optical material.

The depth of the penetrating electron beam and the resulting thickness of the altered refractive index layer are determined by the dose, voltage and duration of the electron beam and accordingly can vary from the upper surface of the starting optical material layer to the lower surface of the microlens structure.

The electron beam can provide a uniform refractive index n1to the resulting irradiated optical material with adjacent sections of different refractive indexes, as discussed inFIG. 8, to form a refractive lens. Or the electron beam can provide a gradient refractive index n2to n1to the resulting irradiated optical material adjacent sections of different refractive indexes, as discussed inFIG. 11, to form a gradient index (GRIN) lens.

Multiple masking steps can provide multiple sections with multiple different refractive indexes in the same optical material layer formed from the same optical material. The multiple sectioned optical material layer with multiple different refractive indexes can be used as a fresnel lens.

The electron beam can be incident at an angle to the aperture mask and the surface of the starting optical material layer to form a tilted refractive index gradient.

As shown in the alternate embodiment ofFIG. 15A, the starting optical material layer1000is positioned on the substrate layer1002. The electron beam apparatus and method ofFIG. 15are the same as inFIG. 14.

A mask1004with multiple apertures1006is positioned between the electron beam source (not shown in this Figure) and the starting optical material layer1000. The starting optical material layer1006will have an original index of refraction n0and a thickness1008. The mask, starting optical material layer and substrate are all parallel.

A large area electron beam1010is incident at a 15 degree angle to the mask1004and starting optical material1000. The electron beam irradiates the exposed angled sections1012of the starting optical material layer through the apertures1006of the mask1004. The electron beam1010will be absorbed, or otherwise blocked, by the mask1004but will be transmitted through the apertures1006. Infrared radiation beams1014will heat the substrate1002and, by heat transfer through the substrate, will heat the starting optical material1000.

As shown inFIGS. 15A and 15B, the electron beam1010fully penetrates the cross-sectional depth or thickness1016of the optical material layer1000to the lower surface1018of the optical material layer1000and the upper surface1020of the substrate1002in the first exposed sections1012of the optical material layer1000through the apertures1006.

The exposed sections will have a varying gradient index of refraction from n1to n2by depth, with the upper refractive index n2closer to the upper surface1022being higher than the lower refractive index n1closer to the lower surface1018through the full thickness1008of the optical material layer1000. Both refractive indexes n1to n2are higher than the original index of refraction n0in the alternating section.

The second section1024of the optical material layer100, which was not exposed to the electron beam irradiation due to the blocking or absorbing by the mask1004, will have the original index of refraction n0of the starting optical material layer.

As shown inFIG. 15B, the aperture mask1004is removed. The optical material layer1000is removed from the substrate1002by conventional chemical, etching, physical means or the use of a release layer, as discussed previously.

The alternating first sections1012of high refractive index and the second sections1024of low refractive index are parallel to each other but are at a 15 degree angle to the upper surface1022and lower surface1018of the optical material layer1000and will form a tilted refractive index gradient. Since the starting optical material layer is one layer, after electron beam irradiation, the first section is integral and positioned adjacent to the second section within the optical material layer.

The tilted index gradient can be used as an output coupling device, a diffraction grating or a beam-splitter. Light propagating within the alternating sections of low and varying high refractive index in the resulting optical material layer will be extracted by the tilted gradient.

The mask serves to restrict the electron beam spatially limiting its irradiation to the apertured sections of the optical material layer.

The depth of the penetrating electron beam and the resulting thickness of the altered refractive index layer are determined by the dose, voltage and duration of the electron beam and accordingly can vary from the upper surface of the starting optical material layer to the lower surface of the gradient index structure.

The electron beam can provide a uniform refractive index n1to the resulting irradiated optical material with adjacent sections of different refractive indexes, as discussed inFIG. 8, to form a diffraction grating or beam-splitter.

Multiple masking steps can provide multiple sections for the tilted index gradient with multiple different refractive indexes in the same optical material layer formed from the same optical material.

The electron beam with multiple masking steps can form a binary diffractive optical element of the same optical material.

As shown inFIG. 16A, the substrate1100is a support ring with an upper surface1102and a lower surface1104. The starting optical material layer1106has an upper surface1108and a lower surface1110.

A small portion1112of the lower surface1110of the starting optical material layer is deposited, bonded, coated, or otherwise positioned on the upper surface1102of the substrate support ring. A large portion1114of the lower surface1110of the starting optical material layer remains exposed.

The starting optical material layer1106will have an original index of refraction n0and a first or full thickness1116.

As shown inFIG. 16B, a first aperture mask1118is positioned between the electron beam source (not shown in this Figure) and the starting optical material layer1106. The first mask1118has an upper surface1120and a single first aperture1122.

A first large area electron beam1124is incident at a perpendicular angle to the upper surface1108of the optical material layer1106through the first aperture1122of the first mask1118and irradiates the optical material layer through the first mask aperture1122. The first electron beam1124will be absorbed, or otherwise blocked, by the surface1120of the first mask1118but will be transmitted through the first mask aperture1122. First infrared radiation beams1126will heat the exposed portion1114of the lower surface1110of the starting optical material1106.

As shown inFIG. 16C, the first electron beam1124fully penetrates the first depth or thickness1126of the optical material layer1106to the lower surface1110of the optical material layer1106in a first section1128of the optical material layer1106.

The remaining section1130of the optical material layer1106was not exposed to the electron beam1124because the mask1118absorbed or blocked the electron beam.

The first section1128of the optical material layer1106will have an index of refraction n1, which is higher than the original index of refraction n0of the starting optical material layer, through the full first thickness1116of the optical material layer. The remaining section1130of the optical material layer1106, which was not exposed to the electron beam irradiation, will have the original index of refraction n0of the starting optical material layer.

The first aperture mask1118is removed.

As shown inFIG. 16D, a second aperture mask1132is positioned between the electron beam source (not shown in this Figure) and the optical material layer1106. The second mask1132has an upper surface1134and a single second aperture1136. The second aperture1136in the second aperture mask is wider than the first aperture122in the first aperture mask.

A second large area electron beam1138is incident at a perpendicular angle to the upper surface1108of the optical material layer1106through the second aperture1136of the second mask1132and irradiates the optical material layer through the second mask aperture1136. The second electron beam1138will be absorbed, or otherwise blocked, by the surface1134of the second mask1132but will be transmitted through the second mask aperture1136. Second infrared radiation beams1140will heat the exposed portion1114of the lower surface1110of the starting optical material1106.

As shown inFIG. 16E, the second aperture mask1132is removed. The optical material layer1106is removed from the substrate1100by conventional chemical, etching, physical means or the use of a release layer, as discussed previously.

The second electron beam1138partially penetrates to a second depth or thickness1142of the optical material layer1106between the upper surface1108and the lower surface1110of the optical material layer1106in a second section1144of the optical material layer1106. The remaining section1146of the optical material layer1106was not exposed to the electron beam1138because the mask1132absorbed or blocked the electron beam.

The second section1144of the optical material layer1106will have an index of refraction n2, which is higher than the original index of refraction n0of the starting optical material layer. The remaining section1146of the optical material layer1106, which was not exposed to the electron beam irradiation, will have the original index of refraction n0of the starting optical material layer.

The second section1144of high refractive index is wider than the first section1128of high refractive index. The second section1144of high refractive index has a shallower depth than the first section1128of high refractive index. The second section1144of high refractive index overlaps in one area1148the first section1128of high refractive index. The overlap area1148will have an index of refraction n3, which is higher than the original index of refraction n0of the starting optical material layer1006.

The two beam exposure through two different size apertures forms a binary diffractive optical element1150. The binary diffractive optical element1150is a two level diffractive element structure. The binary diffractive optical element has a first level1152of the first section1128of high refractive index and a second level1154of the second section1144of high refractive index including the overlap area1148of high refractive index within the remaining section1146of low refractive index of the optical material layer1106.

Multiple masks and multiple electron beam exposure of the starting optical material will provide multiple refractive index sections for a multiple level diffractive structure for the binary diffractive optical element optical element. The binary or multiple level diffractive optical element can be used as a diffraction grating or a beam-splitter.

An aperture mask can be used with the electron beam apparatus and method to provide a waveguide having a core of a high refractive index surrounded or partially surrounded by a cladding layer of a low refractive index of the same optical material.

As shown inFIG. 17A, the substrate1200has an upper surface1202and a lower surface1204. The starting optical material layer1206has an upper surface1208and a lower surface1210. The lower surface1210of the starting optical material layer is deposited, bonded, coated, or otherwise positioned on the upper surface1202of the substrate. The starting optical material layer1206will have an original index of refraction n0and a thickness1212.

As shown inFIG. 17B, an aperture mask1214is positioned between the electron beam source (not shown in this Figure) and the starting optical material layer1206. The mask1214has an upper surface1216and multiple apertures1218.

A large area electron beam1220is incident at a perpendicular angle to the upper surface1208of the optical material layer1206through the apertures1218of the mask1214and irradiates the optical material layer through the mask apertures1218. The electron beam1220will be absorbed, or otherwise blocked, by the surface1216of the mask1214but will be transmitted through the apertures1218. Infrared radiation beams1222will heat the substrate1200through the lower surface1204and, by heat transfer through the substrate, will heat the starting optical material1206.

As shown inFIGS. 17B and 17C, the electron beam1220partially penetrates the depth or thickness1212of the optical material layer1206to a depth or thickness1224between the upper surface1208and the lower surface1210of the optical material1206in the first sections1226exposed to the electron beam through the aperture1218. Another second sections1228of the optical material layer1206were not exposed to the electron beam1220because the mask1214absorbed or blocked the electron beam.

As shown inFIG. 17C, the aperture mask1214is removed. The optical material layer1206is removed from the substrate1200by conventional chemical, etching, physical means or the use of a release layer, as discussed previously.

After heating and electron beam irradiation through the mask aperture, the first sections1226of the optical material layer1206will have an radial gradient index of refraction n2to n1, which is higher than the original index of refraction n0of the starting optical material layer, through the thickness1224of the optical material layer. The second sections1228of the optical material layer1206, which were not exposed to the electron beam irradiation, will have the original index of refraction n0of the starting optical material layer. Since the starting optical material layer is one layer, after electron beam irradiation, the first sections are integral and positioned adjacent to the second sections within the optical material layer.

The first sections1226of high refractive index form a waveguide core layer in the surrounding second sections1228of low refractive index starting optical material layer which functions as a waveguide cladding layer. The waveguide1230extends from the surface1208of the optical material layer1206with its core layer1226partially surrounded by the cladding layer1228.

As shown inFIG. 17D, a second layer1232of starting optical material can be deposited, bonded, coated, or otherwise positioned on the upper surface1208on the core layer1226and the first starting optical material1206to completely surround the high refractive index core layer with a low refractive index cladding layer to form the waveguide1234.

The temperature of the substrate supporting the starting optical material, the voltage of the electron beam, the dose of the electron beam, the duration and number of steps of the electron beam, the use of oxidizing or non-oxidizing gases in the low vacuum atmosphere, can each separately, or in combination, be varied to fabricate a uniform index of refraction for the core layer of the waveguide.

As shown inFIG. 18A, the substrate1300has an upper surface1302and a lower surface1304. The starting optical material layer1306has a stepped pattern upper surface with alternating high upper surfaces1308and low upper surfaces1310across the width of the starting optical material layer. The flat surfaces1308and1310are offset from each other by a first depth1312. The starting optical material layer1306has a flat lower surface1314. The lower surface1314of the starting optical material layer is deposited, bonded, coated, or otherwise positioned on the upper surface1302of the substrate. The starting optical material layer1306will have an original index of refraction n0and a thickness1316.

As shown inFIG. 18B, a first large area electron beam1318is incident at a perpendicular angle to the upper surfaces1308and1310of the optical material layer1306and irradiates the optical material layer. Infrared radiation beams1320will heat the substrate1300through the lower surface1304and, by heat transfer through the substrate, will heat the starting optical material1306.

The electron beam1318partially penetrates the optical material layer to a second depth or thickness1322from the upper surfaces1308and1310into the optical material layer1306. The penetration depth1322is less than the thickness1316of the optical material layer.

As shown inFIG. 18C, the optical material layer1306is removed from the substrate1300by conventional chemical, etching, physical means or the use of a release layer, as discussed previously.

The electron beam irradiation and heating forms first sections1324of refractive index change extending from the high upper surfaces1308into the optical material layer1306to a depth1322and second sections1326of refractive index change extending from the low upper surfaces1310into the optical material layer1306to a depth1322. The first sections1324and second sections1326are identical except for the relative difference in first depth1312into the optical material1306. The first and second sections1324and1326of refractive index change each have an index of refraction have an radial gradient index of refraction n2to n1, which is higher than the original index of refraction n0of the starting optical material layer, through the thickness1322of the optical material layer1306.

A third section1328of the optical material layer1306which were not exposed to the electron beam irradiation, will have the original index of refraction n0of the starting optical material layer.

Since the starting optical material layer is one layer, after electron beam irradiation, the first section is integral and positioned adjacent to the third section within the optical material layer and the second section is integral and positioned adjacent to the third section within the optical material layer.

The first sections1324of high refractive index form a waveguide core layer in the surrounding third section1328of low refractive index starting optical material layer which functions as a waveguide cladding layer. The waveguide1330extends from the surface1308of the optical material layer1306with its core layer1324partially surrounded by the cladding layer1328.

The second sections1326of high refractive index form a waveguide core layer in the surrounding third section1328of low refractive index starting optical material layer which functions as a waveguide cladding layer. The waveguide1330extends from the surface1308of the optical material layer1306with its core layer1326partially surrounded by the cladding layer1328.

As shown inFIG. 18D, a second layer1332of starting optical material can be deposited, bonded, coated, or otherwise positioned on the upper surface1308on the core layers1324and1326and the first starting optical material1306to completely surround the high refractive index core layer with a low refractive index cladding layer to form the waveguides1334.

The variable depths of the upper surface allow for precise positioning of the core layer of the waveguide in the cladding layer. The variable spacing between the waveguides allows for precise positioning relative to each other.

The temperature of the substrate supporting the starting optical material, the voltage of the electron beam, the dose of the electron beam, the duration and number of steps of the electron beam, the use of oxidizing or non-oxidizing gases in the low vacuum atmosphere, can each separately, or in combination, be varied to fabricate a uniform index of refraction for the core layer of the waveguide.

As shown inFIG. 19A, the substrate1400is a support ring with an upper surface1402and a lower surface1404. A first optical material layer1406has an upper blazed surface1408and a lower surface1410. A small portion1412of the lower surface1410of the starting optical material layer is deposited, bonded, coated, or otherwise positioned on the upper surface1402of the substrate support ring. A large portion1414of the lower surface1410of the starting optical material layer remains exposed.

A second optical material layer1416has a blazed upper surface1418and a blazed lower surface1420. A third optical material layer1422has an upper surface1424and a blazed lower surface1426.

The lower blazed surface1420of the second optical material layer1416is deposited, bonded, coated, or otherwise positioned on the upper blazed surface1408of the first optical material layer1406. The lower blazed surface1426of the third optical material layer1422is deposited, bonded or otherwise positioned on the upper blazed surface1418of the second optical material layer1416. The second optical material layer1406will have an original index of refraction n0. The first and third optical material layers will be formed of different material than the second optical material layer but will also have an index of refraction of n0.

As shown inFIG. 19B, an aperture mask1428is positioned between the electron beam source (not shown in this Figure) and the third optical material layer1422. The mask1428has an upper surface1430and a single aperture1432.

A large area electron beam1434is incident at a perpendicular angle to the upper surface1424of the third optical material layer1422through the aperture1432of the mask1428and irradiates the third optical material layer1422and the underlying second optical material layer1416through the mask aperture1432. The electron beam1434will be absorbed, or otherwise blocked, by the surface1430of the mask1428but will be transmitted through the aperture1432. Infrared radiation beams1436will heat the first optical material layer1406through the exposed portion1414of the lower surface1410and, by heat transfer through the first optical material layer1406, will heat the second optical material layer1416.

The electron beam1434fully penetrates the third optical material layer1422and fully penetrates the second optical material layer1416to the upper surface1408of the first optical material layer1406in the first section1438of the second optical material layer1426exposed to the electron beam through the aperture1432. A second section1440of the second optical material layer1416was not exposed to the electron beam1434because the mask1428absorbed or blocked the electron beam. The electron beam irradiation will not effect the third optical material layer1422. The electron beam irradiation will effect the second optical material layer1416, which is formed of a different optical material than the third and first optical material layers.

As shown inFIG. 19C, the substrate1400is removed from the first optical material layer1406by conventional chemical, etching, physical means or the use of a release layer, as discussed previously.

After heating and electron beam irradiation through the mask aperture, the first section1438of the second optical material layer1416will have a radial gradient index of refraction n2to n1, which is higher than the original index of refraction n0of the second optical material layer1416and higher than the index of refraction n0of the first and third optical material layers1406and1422, through the thickness1442of the second optical material layer1416. The second section1440of the second optical material layer1406, which was not exposed to the electron beam irradiation, will have the original index of refraction n0of the second optical material layer1416.

The first section1438of high refractive index forms a waveguide core layer in the surrounding second optical material layer1416, first optical material layer1406and third optical material layer1422of low refractive index which function as a waveguide cladding layer.

The waveguide1444extends from the upper surface grating1446from the upper blazed surface1418to the lower surface grating1448from the lower blazed surface1420with its core layer1438partially surrounded by the cladding layers1416,1406, and1422.

The temperature of the substrates supporting the starting optical material, the voltage of the electron beam, the dose of the electron beam, the duration and number of steps of the electron beam, the use of oxidizing or non-oxidizing gases in the low vacuum atmosphere, can each separately, or in combination, be varied to fabricate a uniform index of refraction for the core layer of the waveguide.

As shown inFIG. 20A, the substrate1500is a support ring with an upper surface1502and a lower surface1504. The starting optical material layer1506has an upper surface1508and a lower surface1510. A small portion1512of the lower surface1510of the starting optical material layer1506is deposited, bonded, coated, or otherwise positioned on the upper surface1502of the substrate support ring1500. A large portion1514of the lower surface1510of the starting optical material layer1506remains exposed. The starting optical material layer1506will have an original index of refraction n0and a thickness1516.

As shown inFIG. 20B, a first embossed wax structure1518has a concave curved upper surface1520and a flat lower surface1522. The lower surface1522of the first embossed structure1518is deposited on the upper surface1508of the starting optical material layer1506. A second embossed wax structure1524has a concave curved lower surface1526and a flat upper surface1528. The upper surface1528of the second embossed structure1524is deposited on the lower surface1510of the starting optical material layer1506. The first and second embossed wax structures are identical in shape and aligned in mirror image fashion on opposite surfaces of the starting optical material layer.

A first large area electron beam1530is incident at a perpendicular angle to the upper surface1520of the first embossed structure1518and irradiates the first embossed structure1518and the starting optical material layer1506. Infrared radiation beams1532will heat the starting optical material1506from an angle to the lower surface1510of the starting optical material layer1506.

The first electron beam1530fully penetrates the first embossed structure1518and partially penetrates the starting optical material layer1506through its upper surface1508between the upper surface1508and the lower surface1510of the optical material layer.

A second large area electron beam1534is incident at a perpendicular angle to the lower surface1526of the second embossed structure1524and irradiates the second embossed structure1524and the starting optical material layer1506. Infrared radiation beams1536will heat the starting optical material1506from an angle to the upper surface1508of the starting optical material layer1506.

The second electron beam1534fully penetrates the second embossed structure1524and partially penetrates the starting optical material layer1506through its lower surface1510between the lower surface1510and the upper surface1508of the optical material layer.

The first electron beam and the second electron beam can irradiate the starting optical material layer simultaneously.

As shown inFIG. 20C, the first embossing structure1518and the second embossing structure1524are removed from the optical material layer1506by conventional means. The substrate1500is removed from the first optical material layer1506by conventional chemical, etching, physical means or the use of a release layer, as discussed previously.

The partial penetration of the first electron beam will form a first section1538in the optical material layer1506having a radial gradient index of refraction n2to n1, which is higher than the original index of refraction n0of the optical material layer. The first section1538extends from the upper surface1508into the optical material layer1506past the midpoint1540of depth1516towards the lower surface1510in a semi-curved area1542. The semi-curved area is in proportion to the electron beam irradiation through the curved surface of the embossed structure.

The partial penetration of the second electron beam will form a second section1544in the optical material layer1506having a radial gradient index of refraction n2to n1, which is higher than the original index of refraction n0of the optical material layer. The first section extends from the lower surface1510into the optical material layer1506past the midpoint1540of depth1516towards the upper surface in a semi-curved area1546. The semi-curved area is in proportion to the electron beam irradiation through the curved surface of the embossed structure.

A third section1548of the surrounding optical material layer1506, which was not exposed to the electron beam irradiation, will have the original index of refraction n0of the starting optical material layer.

The first high refractive index section1538and second high refractive index section1544will overlap in an overlapping section1550in the optical material layer1506. The overlap section1550will be exposed to irradiation from both the first and second electron beams. The overlap section will have a radial gradient index of refraction n4to n3, which is higher than the radial gradient index of refraction n2to n1of the first and second sections1538and1544and higher than the original index of refraction n0of the optical material layer.

The high refractive index overlap section1550forms a waveguide core layer with the first section1538, second section1544and third section1548of lower refractive indexes being the cladding layer of the waveguide surrounding the core layer.

The waveguide1552extends through the midpoint1540of the optical material layer1506completely surrounded by cladding layers1538,1544and1548.

Since the starting optical material layer is one layer, after electron beam irradiation, the first section is integral and positioned adjacent to the third section within the optical material layer, the second section is integral and positioned adjacent to the third section and the overlapping section is integral and positioned adjacent to the first section, second section and third section within the optical material layer.

Alternately, only one heating source will heat the starting optical material layer with infrared radiation beams1532from below the starting optical material layer or infrared radiation beams1536from above the starting optical material layer.

Also alternately, the formation of the waveguide can be a two step process with the first step being positioning the first embossing structure and the first electron beam irradiation from above the optical material layer and the second step of the positioning of the second embossing structure and the second electron beam irradiation from below the optical material layer.

As shown inFIG. 20D, the first and second wax structures (not shown in this Figure) can be slightly out of alignment. The first section1554of high refractive index will form a first waveguide core layer on the upper surface1508with the partially surrounding starting optical material layer1506being the cladding layer of the first waveguide. The second section1556of high refractive index will form a second waveguide core layer on the lower surface1510with the partially surrounding starting optical material layer1506being the cladding layer of the second waveguide. In this instance, the first section1554of high refractive index and the second section1556of high refractive index do not overlap in the optical material layer1506.

The embossed structures can be varied in the shape of the surfaces. The waveguides formed by the embossed structures cane be overlapping or isolated depending upon the alignment or nonalignment of the embossed structures on opposite surfaces of the optical material layer.

The temperature of the substrates supporting the starting optical material, the voltage of the electron beam, the dose of the electron beam, the duration and number of steps of the electron beam, the use of oxidizing or non-oxidizing gases in the low vacuum atmosphere, can each separately, or in combination, be varied to fabricate a uniform index of refraction for the core layer of the waveguide.

The use of masks in the electron beam apparatus and method allows the fabrication of optical interconnects in complex three dimensional optical elements by providing narrow waveguides and waveguides that can align between layers as shown inFIG. 21.

As shown inFIG. 21, a first waveguide1600in the upper layer1602is patterned to divide into a first branch waveguide1604and a second branch waveguide1606. The first branch waveguide1604continues on in the upper layer1602. The second branch waveguide1606interconnects in a mating pattern to a second waveguide1608in the lower layer1610.

A laser diode1612is mounted such that an emitted light beam1614is coupled into the upper top layer1602while the lower bottom layer1610acts as a spacer to physically set the upper top layer1602at the appropriate height from a substrate1616. The light beam1614emitted by the laser diode1612couples into the first waveguide1610as is illustrated by the dashed lines in the top layer. Halfway through the upper layer1602, the first waveguide1610splits into two branches1604and1606. A first branch waveguide1604continues to guide the light beam164within the upper top layer1602. A second branch waveguide1606continues to guide the light beam1614and transitions into the lower bottom layer1610and a second waveguide1608. This transition can be created by varying the penetration depth.

These optical material layers can be used as overlays on active components such as microprocessors, Vertical Cavity Simulated Emission Lasers (VCSELs), laser diodes, and Micro-Electro-Mechanical Systems (MEMS) devices. Lift off techniques using soluble or meltable temporary attachment means are also embodied in this invention. A lifted off optical material layers or a supported optical material layers can be attached to non-flat substrates and incorporated into or on a printed circuit board. These optical material layers can be combined with optical components such as prisms, gratings, waveplates and optical amplifiers.

The electron beam apparatus and method can form an optical fiber for use as a waveguide having a core of a high refractive index surrounded by a cladding layer of a low refractive index formed of the same optical material.

As shown inFIG. 22A, a cylindrical strand1700of starting optical material has an outer surface1702and a center1704. The starting optical material strand1700will have an original index of refraction n0and a diameter1706. The strand is supported and mounted between a first roller1708and a second roller1710. The first and second rollers1708and1710rotate in the same direction, driven by a conventional motor (not shown in this Figure), as is known in the art. The strand1700rotates along its length as the rollers rotate.

As shown inFIG. 22B, a large area electron beam1712is incident at a perpendicular angle to the outer surface1702of the optical material strand1700and irradiates the optical material strand. Infrared radiation beams1714will heat the starting optical material1700through the outer surface1702on the side of the strand away from the electron beam irradiation. The strand rotates during electron beam irradiation and heating.

The electron beam1712partially penetrates optical material strand1700to a depth or thickness1716through the outer surface1702past the center1704of the strand.

As shown inFIG. 22C, the electron beam1712irradiates the cylindrical strand1700of optical material unevenly across its diameter1706. The first electron beam irradiation area1718at 0 degrees of rotation extends past the center1704of the strand1700. The second electron beam irradiation area1720at 120 degrees of rotation extends past the center1704of the strand1700. The third electron beam irradiation area1722at 240 degrees of rotation extends past the center1704of the strand1700.

An inner cylindrical section1724of the cylindrical strand1700having a diameter1726around the center1704receives constant overlapping electron beam irradiation during rotation of the strand. An outer section1728near the outer surface1702of the cylindrical strand between the diameter1726of the inner cylindrical section and diameter1706of the cylindrical strand receives intermittent electron beam irradiation during an angular range of degrees of rotation. The electron beam will irradiate the cylindrical strand though a full 360 degrees of rotation. The areas at 0 degrees, 120 degrees and 240 degrees are merely illustrative examples.

As shown inFIG. 22D, after heating and electron beam irradiation, the outer section1728near the outer surface1702of the cylindrical strand1700will have a radial gradient index of refraction n2to n1from diameter1726to the outer surface1702which is higher than the original index of refraction n0of the starting optical material.

The inner cylindrical section1724of the cylindrical strand1700will have a radial gradient index of refraction n4to n3from center1704to diameter1726which is higher than the original index of refraction n0of the starting optical material layer and which is higher than the gradient index of refraction n2to n1of the outer section.

Since the starting optical material strand is one strand, after electron beam irradiation, the inner section is integral and positioned adjacent to the outer section within the optical material.

The inner section1724of the cylindrical strand1700forms the high refractive index core layer of a waveguide1730. The outer section1728of the cylindrical strand1700forms the low refractive index cladding layer of a waveguide1730. The cladding layer surrounding the core layer forms a waveguiding optical fiber1730of the same optical material.

To provide uniform exposure of the cylindrical optical material1700along its cross-sectional diameter, the strand1700may rotate under the electron beam1712as seen inFIG. 22Bor the electron beam1712may rotate around the strand1700(not shown in this Figure) or both the strand1700and electron beam1712may rotate in opposite directions or at differing speeds in the same direction (not shown in this Figure).

The temperature of the substrate supporting the starting optical material, the voltage of the electron beam, the dose of the electron beam, the duration and number of steps of the electron beam, the use of oxidizing or non-oxidizing gases in the low vacuum atmosphere, can each separately, or in combination, be varied to fabricate a uniform index of refraction for the cladding layer or the core layer of the optical fiber.

While there has been described herein the principles of the invention, it is to be clearly understood to those skilled in the art that this description is made only by way of example and not as a limitation to the scope of the invention. Accordingly, it is intended, by the appended claims, to cover all modifications of the invention which fall within the true spirit and scope of the invention.