Distributing clock signals using metamaterial-based waveguides

Various embodiments of the present invention are directed to global interconnects that employ metamaterial-based waveguides to distribute clock signals to IC internal components. In one embodiment of the present invention, a global interconnect includes an electromagnetic radiation source that radiates electromagnetic waves. The global interconnect also includes a metamaterial-based waveguide that directs a transverse magnetic field mode of the electromagnetic wave to antennae of the internal components in order to induce an oscillating current within the internal components that serves as the clock signal.

TECHNICAL FIELD

The present invention relates to integrated circuits, and, in particular, to waveguides composed of metamaterials that can be used to distribute clock signals to integrated circuit internal components.

BACKGROUND OF THE INVENTION

During the past fifty years, the electronics and computing industries have steadily increased the speed of digital computing devices and made remarkable progress in reducing the size and speed of computing device internal components, such as logic circuits and memory. Internal components are typically integrated on a single substrate and referred to as a “chip or “integrated circuit” (“IC”). Networks of electrical interconnections, referred to as “global interconnects,” link these internal components, such as interconnections that link logic and memory. Global interconnects are composed of signal lines that transmit data between internal components and distribute power and clock signals to internal components.

Clock signals are electrical signals that cycle between a high electrical state and a low electrical state at a specific rate. Typical ICs use a clock signal to synchronize the operation of different internal components. Internal components receiving a clock signal may become active on either the rising edge or the falling edge of each cycle of the clock signal. The rate at which the clock signal cycles between a high electronic state and a low electronic state is called the “clock rate.” The clock rate, measured in cycles per second (“Hz”), is the rate at which an IC performs its most basic operations, such as transmitting data between internal components. As the clock rate is increased, the internal components generally transmit data and carry out instructions more quickly.

In order to decrease the amount of time needed to transmit data between internal components, ICs are typically designed so that the distances between internal components exchanging large amounts of data are shorter than the distances between internal components exchanging small amounts of data. However, a clock signal is typically distributed from a single clock signal source to each internal component over a single global interconnect. As a result, clock signals traverse the longest signal line distances, and operate at the highest speeds of any signal, either control or data, transmitted within the IC. The clock signal source may include a crystal, such as a quartz crystal, that generates the clock signal by oscillating at a predictable rate within the megahertz (“MHz”) or gigahertz (“GHz”) frequency ranges. For example, crystal-based clock rates as high as 3 GHz have been achieved.

FIGS. 1A-1Billustrate an exemplary global interconnect that distributes a clock signal to numerous internal components of a hypothetical IC. InFIG. 1A, IC101is composed of a number of internal components identified by rectangles. For example, rectangles102-104represent random access memory and rectangle105represents a central processing unit. A clock signal generated by clock signal source106is distributed to the internal components via a global interconnect comprising a network of signal lines, such as signal line107.FIG. 1Bis a plot of an exemplary clock signal distributed by clock signal source106. The internal components of IC101may each be activated on a rising edge of a clock cycle, such as clock cycle edge108. Because the global interconnect employs signal lines located between the internal components, internal components located farthest from clock signal source106, such as internal component102, may receive a clock cycle later than internal components located closer to clock signal source106. As a result, the internal components do not all receive the same clock signal at the same time. For example, stippled internal component105may receive clock cycle110at about the same time blank internal component109receives clock cycle111,

In spite of efforts to improve the design of IC architectures and the design of global interconnects to distribute clock signals, the percentage of a chip that can be reached within a few clock cycles has continued to decrease as the number of internal components integrated on a single chip has increased, and clock frequencies have increased. In addition, the global interconnects employed are rapidly approaching fundamental physical limits with respect to the information carrying capacity of metal wires. In general, as IC internal components and electronic interconnects shrink from microscale dimensions to nanoscale dimensions, intrinsic capacitance of the electronic interconnections greatly increases and exceeds that of the nanoscale internal components. As a result, the information carrying capacity of each wire in a global interconnect decreases, and closely spaced wires cannot be accessed at high speeds without creating interference, including inducing currents in adjacent wires. Thus, even though the internal component density can be increased by decreasing the size of IC internal components, the number of transistors that can be reached in one clock cycle of a clock signal may significantly decrease. Manufacturers, designers, and users of computing devices have recognized a need for new global interconnects that can uniformly distribute clock signals and can accommodate the ever increasing demand for higher clock rates.

SUMMARY OF THE INVENTION

Various embodiments of the present invention are directed to global interconnects that employ metamaterial-based waveguides to distribute clock signals to IC internal components. In one embodiment of the present invention, a global interconnect includes an electromagnetic radiation source that radiates electromagnetic waves. The global interconnect also includes a metamaterial-based waveguide that directs a transverse magnetic field mode of the electromagnetic wave to antennae of the internal components in order to induce an oscillating current within the internal components that serves as the clock signal.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments of the present invention are directed to global interconnects that employ metamaterial-based waveguides to distribute clock signals to internal components of an IC. An electromagnetic radiation source radiates electromagnetic waves of radiation. Metamaterial-based waveguides, composed of microstructures that confine and direct a transverse magnetic field mode having a frequency within a specific frequency range of the electromagnetic waves, are located near the internal components so that the transverse magnetic field mode transmitted through the waveguides from the electromagnetic radiation source can induce an oscillating current in antennae located on the internal components. The oscillating current induced in the antenna of an internal component serves as a clock signal that can be used to synchronize operation of each internal component.

The present invention is described below in the subsections: (1) metamaterials that interact with transverse magnetic field modes of electromagnetic waves, and (2) distributing clock signals using non-magnetic, capacitor-based metamaterials.

Metamaterials that Interact with Transverse Magnetic Field Modes of Electromagnetic Waves

Electromagnetic radiation propagating in free space can be characterized by electromagnetic waves that consist of oscillating electric field, {right arrow over (E)}, modes (“TE”) and corresponding magnetic field, {right arrow over (B)}, modes (“TM”) that are orthogonal to one another and transverse to the direction of propagation of the electromagnetic waves.FIG. 2illustrates an exemplary TE and an exemplary TM of an electromagnetic wave propagating in free space. InFIG. 2, the electromagnetic wave propagates in the z-direction, as indicated by wavevector kz, with a wavelength λ at the speed of light c. In general, for each TE of a propagating electromagnetic wave, there is a corresponding orthogonally directed TM. For example, inFIG. 2, a TE lying in the xz-plane has a corresponding orthogonal TM lying in the yz-plane.

Electromagnetic waves propagate in various kinds of materials when the wavelengths of the TEs and TMs are longer than the internal structure of the atoms or molecules comprising the materials. As a result, heterogeneous atomic structural details of a material can conceptually be replaced with a homogeneous material characterized by two macroscopic electromagnetic parameters, electric permittivity, ε0, and magnetic permeability, μ0. The electric permittivity ε0and magnetic permeability μ0relate the electric and magnetic field modes of an electromagnetic wave propagating in free space to an electric displacement field, {right arrow over (D)}, mode and a magnetic field, {right arrow over (H)}, mode for an electromagnetic wave propagating in a material as follows:

B→=μ0⁢H→E→=1ɛ0⁢D→
The electric permittivity ε0represents the ability of a material to store electrical potential energy under the influence of an electric field, and the magnetic permeability μ0represents the degree to which a material can modify the flux of a magnetic field.

The parameters ε0and μ0can be characterized for any material fabricated from a collection of objects having sizes and spacings that are much smaller than the wavelength λ. In other words, the wavelength λ can be used to determine whether a material fabricated from a collection of objects can be considered a homogeneous or heterogeneous material. Metamaterials are artificial materials that are fabricated from a collection of microscale objects that are larger than atoms and molecules. The microscale objects comprising a metamaterial can be arranged in a regular lattice identified by the simplest repeating unit called a “unit cell.” For example, a metamaterial unit cell can be body-centered cubic, face-centered cubic, or cubic, just to name a few.FIG. 3illustrates a cubic unit cell for a three-dimensional lattice of microscale objects comprising a metamaterial. InFIG. 3, the microscale objects comprising a metamaterial are identified by closed circles located at the corners of the unit cell, such as closed circle301. The constant a represents the space separating the objects. When the space between objects of a unit cell satisfies the wavelength condition:

a⁢⁢<<λ=2⁢⁢π⁢⁢cω,where ω is an angular frequency of a propagating electromagnetic wave,
the metamaterial can be characterized as a homogeneous material and the electromagnetic waves propagating through the metamaterial are not effected by the internal structure of the metamaterial. However, when the wavelength condition is not satisfied, the internal structure of the metamaterial can diffract as well as refract propagating electromagnetic waves.

The objects used to fabricate metamaterials can be non-magnetic conductors called “microstructures,” that, depending on the structure, dimensions, and arrangement of the microstructures, can affect the TMs of propagating electromagnetic waves, even though the dimensions of the metamaterial unit cell and the size of the microstructures satisfy the wavelength condition above. As a result, metamaterials composed of microstructures have an associated effective permeability parameter, μeff, that relates the average free space TMs to the average TMs for an electromagnetic wave propagating in a metamaterial of microstructures, as follows:
{right arrow over (B)}ave=μeffμ0{right arrow over (H)}ave
{right arrow over (B)}aveis the magnetic field averaged over local variations in the TMs. When the effective permeability μeffis greater than zero, the microstructures have little to no effect on the TMs of an electromagnetic wave propagating in a metamaterial. However, metamaterials can be fabricated with microstructures having dimensions and arrangements that result in an effective permeability μeffwith a negative value even though the wavelength condition is satisfied. As a result, certain metamaterials can be used to confine and direct the propagation of TMs of electromagnetic waves.

The effective permeability μeffof a metamaterial of microstructures can be determined by first determining the average free space {right arrow over (B)}aveand metamaterial {right arrow over (H)}avefields and then solving for μeff. The average fields can be determined for a unit cell, such as the cubic unit cell described above with reference toFIG. 3, using Maxwell's curl equations in integral form:

∫C⁢H→·ⅆl→=∂∂t⁢∫S⁢D→·ⅆS→∫C⁢E→·ⅆl→=-∂∂t⁢∫S⁢B→·ⅆS→where t is time, andC is a loop that encloses a surface area S of a face of the unit cell.
The components of {right arrow over (H)}aveare determined by averaging the {right arrow over (H)} field along each of the three axes of the unit cell. For example, for the cubic unit cell shown inFIG. 3, the components of {right arrow over (H)}aveare determined by:

(Have)x=1a⁢∫(0,0,0)(a,0,0)⁢H→·ⅆr→⁢(Have)y=1a⁢∫(0,0,0)(0,a,0)⁢H→·ⅆr→⁢(Have)z=1a⁢∫(0,0,0)(0,0,a)⁢H→·ⅆr→
The edges of a unit cell do not intersect with the microstructures located at the corners of the unit cell. As a result, parallel components of {right arrow over (H)}aveare continuous across the surface of the metamaterial.

The components of {right arrow over (B)}aveare determined by averaging the {right arrow over (B)} field over three faces of the unit cell. For example, for the cubic unit cell shown inFIG. 3, the components of {right arrow over (B)}aveare determined by:

After the components of the average {right arrow over (H)}aveand average {right arrow over (B)}avehave been determined, the effective permeability is given by:

Metamaterials can be identified by the number of directions in which the microstructures are periodic. For example, a planar lattice of microstructures that are periodic in two directions comprises a two-dimensional metamaterial.FIG. 4illustrates a metamaterial400comprising a two-dimensional square lattice of microstructures. InFIG. 4, each microstructure, such as microstructure401, is a coiled, non-magnetic, conductive metallic sheet that forms a cylindrical capacitor called a “Swiss roll.” The unit cell of metamaterial400is a square planar lattice of four Swiss rolls having spacing a.FIG. 5illustrates an enlargement of one of the Swiss rolls shown inFIG. 4. Each Swiss roll has a radius r and a distance d separating each coil.

The effect a metamaterial comprising Swiss rolls can have on the TM of electromagnetic waves depends on the radius r, the distance d, the spacing a, and the number of coils N, as indicated by the functional form of the effective permeability for a a square unit cell of Swiss rolls given by:

μeff=1-π⁢⁢r2a21+2⁢⁢σ⁢⁢iω⁢⁢r⁢⁢μ0⁡(N-1)-d⁢⁢c22⁢⁢π2⁢r3⁡(N-1)⁢ω2where σ is the resistance of the coiled sheets,i is √{square root over (−1)}, andω is the angular frequency of electromagnetic radiation applied to the metamaterial.

FIG. 6is a plot of Re(μeff) versus angular frequency ω for a square unit cell of Swiss rolls. InFIG. 6, horizontal line601is the angular frequency axis, and vertical line602is the effective permeability axis. Point603identifies the frequency at which μeffdiverges and is given by:

ω0=d⁢⁢c22⁢⁢π2⁢r3⁡(N-1)
Point604identifies a magnetic plasma frequency given by:

ωm⁢⁢p=d⁢⁢c2(1-π⁢⁢r2a2)⁢2⁢⁢ω2⁢r3⁡(N-1)
Magnetic plasma frequency ωmpidentifies a lower limit for a range of frequencies above which the TMs of electromagnetic waves do not interact appreciably with the Swiss rolls of metamaterial400shown inFIG. 4. In contrast, the TMs of electromagnetic waves having frequencies in passband605interact strongly with the Swiss rolls by inducing a resonating current j on the coiled sheet of each Swiss roll. The passband605, shown inFIG. 6, can be shifted along axis601to higher or lower frequencies by adjusting the distance d, the radius r, the spacing a, and the number of coils N.

In general, a changing magnetic field applied to a conductor induces an electric current that flows in the conductor. A changing magnetic field that induces a current in the coiled sheets of a Swiss roll can be an oscillating TM of an electromagnetic wave with a frequency that lies in the passband.FIGS. 7A-7Cconceptually illustrate three different snapshots, in time, of induced currents in a coiled sheet of a Swiss roll resulting from a TM of a propagating electromagnetic wave. InFIGS. 7A-7C, electromagnetic radiation is directed perpendicular to the central axis of Swiss roll701, as indicated by wavevector {right arrow over (k)}702.FIG. 7Ashows a maximum upward displacement703of a propagating TM located directly over the central axis of Swiss roll701. In Swiss roll top view705, the upward displacement of the TM creates a capacitance between inner coil turn706and outer coil turn707that enables current j to flow in the direction identified by arrow704.FIG. 7Bshows an inflection point708of a TM located directly over the central axis of Swiss roll701. As a result, in Swiss roll top view709, no capacitance is created between inner coil turn706and outer coil turn707and no current is induced in the coiled sheet of Swiss roll701.FIG. 7Cshows a maximum downward displacement710of a TM located directly over the central axis of Swiss roll701. In Swiss roll top view712, the downward displacement creates a capacitance between inner coil turn706and outer coil turn707that enables current j to flow in the direction identified by arrow711, which is opposite the direction of the current induced by upward displace of the TM, as indicated by arrow704.

The direction of the induced current in Swiss roll701continuously oscillates with the upward and downward oscillating displacement of a propagating TM. However, a wave corresponding to the continuously oscillating current j is phase shifted and lags behind the propagating TM wave.

The Swiss roll microstructures described above with reference toFIGS. 4-7Crepresent just one of many different microstructure shapes that can be used to fabricate two-dimensional metamaterials. For example,FIGS. 8A-8Eillustrate five of many different kinds of microstructure shapes that can be used to fabricate two-dimensional metamaterials. The microstructures shown inFIGS. 8A-8Eare referred to as “split ring resonators” (“SRR”).

A propagating TM of an electromagnetic wave having frequencies in the passband can be confined to the plane of a two-dimensional metamaterial.FIG. 9illustrates a propagating TM of an electromagnetic wave that is confined to the plane of a metamaterial composed of Swiss rolls. InFIG. 9, the electromagnetic waves originate from an electromagnetic radiation source901located at one end of the metamaterial. The wavelength λ of TM902of electromagnetic wave propagating across the metamaterial is longer than the spacing a between Swiss rolls The upward and downward displacement of the propagating TM identified by directional arrows, such as directional arrow903, induces currents in coils of the Swiss rolls that flow in the directions identified by directional arrows904and905. The amount of current induced in the coils of the Swiss rolls is proportional to the amount of upward and downward displacement of the propagating TM. For example, the upward displacement of the TM propagating over row906is larger than the upward displacement of the same TM propagating over row907. As a result, the magnitude of the lagging current induced in the Swiss rolls of row906is larger than the magnitude of the lagging current induced in the Swiss rolls of row907.

Distributing Clock Signals Using Metamaterial-based Waveguides

FIG. 10illustrates a perspective view of an exemplary IC1000with internal components having antennae for receiving a clock signal in the form of a TM of an electromagnetic wave representing one of many possible embodiments of the present invention. InFIG. 10, internal components of IC1000are represented by raised surfaces, such as raised surface1001, that are attached to substrate1002. The internal components can be processing units, logic circuits, or local memory units. Each internal component includes an antenna represented by a box, such as box1003, located on the top surface of each internal component. The antennae are composed of non-magnetic, conducting materials. The regions between internal components, such as region1004, may include a global interconnect composed of a network of signal lines and address lines for distributing data, power, and addresses to each internal component.

A clock signal in the form a TM can be distributed to each internal component of IC1000using two-dimensional metamaterial-based waveguides.FIG. 11illustrates a perspective view of an exemplary global interconnect1100for distributing a clock signal in the form of a TM to the internal components of the IC1000representing one of many possible embodiments of the present invention. InFIG. 11, waveguides1101and1102are two-dimensional metamaterials composed of a square unit cell lattice of microstructures that are located on the top surface of substrate1103. Each waveguide is four microstructures wide. The microstructures are represented by cylinders, such as cylinder1104, and can be Swiss rolls, described above with reference toFIG. 5, or SRRs, such as any of the SRRs shown inFIGS. 8A-8E. The microstructures can be fabricated on substrate1102using lithographic methods that are well-know in the art.

In order to distribute a TM to the internal components of the IC1000, global interconnect1100can be inverted and positioned directly above IC1000.FIG. 12illustrates inverted global interconnect1100positioned directly above the IC1000representing one of many possible embodiments of the present invention. Inverted global interconnect1100is lowered, as indicated by directional arrows1201-1203, and suspended above IC1000by supports located at the corners of IC1000, such as support1204. The supports prevent the microstructures of waveguides1101and1102from contacting the antennae located on the top surface of each internal component.

FIG. 13Aillustrates a cross-sectional view of the IC and global interconnect shown inFIG. 12, that represents one of many embodiments of the present invention. InFIG. 13A, global interconnect1100is suspended above IC1000by supports shown inFIG. 12. Antenna1003is located on the top surface of internal component1001, and waveguide1101is located directly above antenna1003. An oscillating TM in waveguide1101induces an oscillating current in antenna1003. The induced current oscillates at the same rate as the TM propagating in waveguide1101and is used as a clock signal to synchronize the operation of internal component1001with the remaining internal components of IC1000.FIG. 13Billustrates a cross-sectional view of the waveguide shown inFIG. 13A. InFIG. 13B, antenna1003is located directly below the microstructures of waveguide1101.

A tapered optical fiber or tapered coaxial cable can be used to transmit the TM of an electromagnetic wave into the metamaterial-based waveguides. A fraction of the electromagnetic waves propagating parallel to the central axis of a tapered optical fiber or tapered coaxial cable evanesces in all directions perpendicular to the central axis of the optical fiber or coaxial cable. The evanesced electromagnetic waves provide the TMs that propagate in the waveguides of the global interconnect described above with reference toFIGS. 11 and 12.FIG. 14Aillustrates a top view of a tapered optical fiber located along an edge of the inverted global interconnect and integrated circuit shown inFIG. 12representing one of many possible embodiments of the present invention. InFIG. 14A, global interconnect1100is located above IC1000. Dashed line circles, such as dashed line circle1401, identify the microstructures comprising waveguides1101and1102and located on the underside of substrate1103. Tapered optical fiber1402transmits electromagnetic waves in the direction indicated by directional arrow1403. Directional arrows, such as directional arrow1404, represent a fraction of the propagating electromagnetic waves evanescing from optical fiber1402toward global interconnect1100. Filter1405includes slits1406and1407that selectively permit only the evanescing electromagnetic waves that propagate parallel to waveguides1101and1102to enter waveguides1101and1102and prevents other evanescing electromagnetic waves directed outward from tapered optical fiber1402from interacting with IC1000. The microstructures of waveguides1101and1102transmit the TMs of the evanescing electromagnetic waves having frequencies that lie within the passband of the microstructure square unit cell to the end of each waveguide, as indicated by directional arrows1408and1409.

FIG. 14Billustrates a cross-sectional view of the tapered optical fiber and IC shown inFIG. 14A, that represents one of many embodiments of the present invention. InFIG. 14B, an evanescing electromagnetic wave identified by directional arrow1410enters slit1406in filter1405. The TM of the electromagnetic wave is transmitted by waveguide1101. The oscillation in the TM induces a current in the antennae located below waveguide1101, such as antenna1411, that oscillates with the same frequency of the TM. The oscillating current in each antenna is the clock signal that synchronizes the operation of internal components of IC1000.

Metamaterial-based waveguides can be used to transmit TMs with passband frequencies that lie within the gigahertz (“GHz”) as well as terahertz (“THz”) frequency ranges. Table 1 displays limits of two passbands for two square unit cells, each comprising two differently dimensioned Swiss rolls as follows:

TABLE 1draNf0= ω0/2πfmp= ωmp/2π10 μm200 μm500 μm38.5 GHz12 GHz50 nm300 nm750 nm3100 THz160 THz
The frequencies listed in Table 1 indicate that the range of frequencies within the passband increase as the dimensions of the Swiss rolls of a metamaterial decrease. In addition, the frequency data displayed in Table 1 indicates that metamaterial-based waveguides composed of Swiss rolls may be used to achieve GHz as well as THz clock rates.

SRRs, such as the SRRs shown inFIGS. 8A-8E, can also be employed as the microstructures of metamaterial-based waveguides to achieve GHz as well as THz clock rates.FIGS. 15A-15Eillustrate frequencies of a square unit cell composed of the SRR microstructure shown inFIG. 8C, for various microstructure spacings.FIG. 15Aillustrates a square unit cell of a metamaterial comprising the SRR shown inFIG. 8C. InFIG. 15A, the SRRs are spaced by a distance a.FIG. 15Billustrates an enlargement of one of the SRRs shown inFIG. 15A, with the slot length and inner and outer ring distance denoted by s, the wall thickness is denoted by t, and the length of each side is denoted by m.FIG. 15Cdisplays magnetic plasma frequencies of the square unit cell shown inFIG. 15Afor various unit cell spacings a with s equal 70 nm, t equal to 100 nm, m equal to 400 nm, and an SRR height equal to 20 nm.FIG. 15Dis a plot of the magnetic plasma frequencies versus the first 10 lattice spacings displayed inFIG. 15Cand indicates that, as the unit cell spacing increases linearly, the corresponding frequencies within the passband decrease exponentially.FIG. 15Edisplays frequencies for even smaller unit cell spacings of the SRRs and indicates that metamaterial-based waveguides fabricated with lattice spacings between 150 nm to 600 nm transmit TMs of electromagnetic waves with frequencies that lie in the terahertz (“THz”) frequency range. The frequencies displayed inFIGS. 15C and 15Eindicate that clock rates ranging from 10 GHz to 170 THz may be achievable for metamaterial-based waveguides composed of the SRRs shown inFIG. 15B.

Although the present invention has been described in terms of a particular embodiment, it is not intended that the present invention be limited to this embodiment. Modifications within the spirit of the invention are apparent to those skilled in the art. For example, in an alternate embodiment of the present invention, the tapered optical fiber or coaxial cable used to deliver evanescent electromagnetic waves can be located above a substrate containing the metamaterial-based waveguides. In order to transmit a TM along the metamaterial-based waveguides, the microstructures are embedded in the substrate and extend above the top surface of the substrate and extend below the bottom surface of the substrate.FIGS. 16A-16Billustrate a tapered optical fiber located above a substrate with microstructures that extend above and below the substrate top and bottom surfaces, that represents one of many possible embodiments of the present invention. InFIG. 16A, the microstructures comprising waveguides1601and1602extend through substrate1603and are identified by circle1604. IC1000, shown inFIG. 10, is located beneath substrate1603. Tapered optical fiber1605lies above substrate1603and transmits electromagnetic radiation perpendicular to waveguides1601and1602in the direction identified by directional arrow1606. Hash-marked circles, such as hash-marked circle1607, represent microstructure of waveguides1601and1602that extend above substrate1603and lie below tapered optical fiber1605.

FIG. 16Billustrates a cross-sectional view of the tapered optical fiber and IC shown inFIG. 16A. InFIG. 16B, an evanescing electromagnetic wave identified by directional arrow1608induces oscillating currents in the microstructures located directly below tapered optical fiber1605. The oscillating currents induce a TM that propagates on waveguide1601. The oscillation in the TM induces an oscillating current in the antenna located below waveguide1601that oscillates with the same frequency as TM. The oscillating current in each antenna is the clock signal that synchronizes the operation of internal components of IC1000.

FIGS. 17A-17Billustrate two tapered optical fibers located above a substrate with microstructures that extend above and below the substrate top and bottom surfaces that represents one of many possible embodiments of the present invention. InFIG. 17A, the microstructures comprising waveguides1701and1702extend through substrate1703and are identified by circles, such as circle1704. IC1000, shown inFIG. 10, is located beneath substrate1703. Tapered optical fibers1705and1706are suspended above substrate1703and transmit electromagnetic radiation parallel to waveguides1701and1702. Hash-marked circles, such as hash-marked circle1707, represent microstructure of waveguides1701and1702that extend above substrate1703and lie below tapered optical fibers1705and1706.

FIG. 17Billustrates a cross-sectional view of the tapered optical fiber and IC shown inFIG. 17A. InFIG. 17B, a TM of an evanescing electromagnetic wave induces oscillating currents in the microstructures located directly below tapered optical fiber1705. The oscillating currents induce a TM that propagates on waveguide1701. The oscillation in the TM induces an oscillating current in the antennae located below waveguide1701that oscillates with the same frequency as TM. The oscillating current in each antenna is the clock signal that synchronizes the operation of internal components of IC1000.