JP2006276184A - Optical logic circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical logic circuit capable of complicated signal processing using a plurality of resonators. <P>SOLUTION: The optical logic circuit comprises the plurality of resonators and a plurality of waveguides coupled to the plurality of resonators, which have at least one identical resonance frequency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical logic circuit, and more particularly to an optical logic circuit including a plurality of resonators.

  In order to realize ultra high-speed optical digital processing, identification and reproduction functions like flip-flop circuits are essential, but until now it has been difficult to construct complex optical circuits having such functions in the optical domain. This is the current situation. An optical device based on a photonic crystal has an overwhelming degree of design freedom compared to the conventional one, and is considered to possibly break the above limit.

  One configuration for realizing an optical functional device is a coupled system of a resonator and a waveguide as shown in FIGS.

  FIG. 1A includes a waveguide 1 and a resonator 2. When the resonator 2 is configured with a ring (disk) resonator so that only a clockwise circular mode is excited in the resonator, light resonates with the resonator 2, regardless of whether it is not resonating. Output from the output port. However, the phase relationship is reversed between the resonated output light and the non-resonant output light.

  If such a coupling system is constituted by a photonic crystal, the optical device can be further miniaturized. Since this coupling system can confine light more efficiently in a minute region than a ring resonator or the like, enhancement of the interaction between light and a medium can be expected compared to conventional optical devices. In this case, the resonator 2 can also be excited in a counterclockwise circular mode, and light is also output from the leftmost input port of the waveguide 1.

  That is, in the configuration of FIG. 1A, light is temporarily stored in the resonator only when the light resonates with the resonator 2, and then reflected to the leftmost input port of the waveguide 1. Other than the resonance frequency, light cannot enter the resonator 2 and is output from the output port at the right end of the waveguide 1.

  If a photonic crystal is used, the configuration shown in FIG. 1B is possible. This configuration is called a two-port resonant tunneling filter. Light is temporarily stored in the resonator 4 only when light incident from the waveguide 5 resonates with the resonator 4, and then output from the output port of the waveguide 6. Is done. Light other than the resonance frequency cannot enter the resonator 4 and is reflected by the input port.

  The resonance frequency of the resonators 2 and 4 included in these coupling systems depends on the refractive index of the medium constituting the resonators 2 and 4, and the refractive index can be controlled by the light intensity. Functions as a simple optical switch that can control with light intensity whether the resonator and light resonate (on state) or not (off state).

  For example, a switch characteristic in which the state changes from off to on when light slightly shifted from the resonance frequency is gradually increased is shown. The resonant tunneling filter also exhibits bistable characteristics. In other words, it shows a hysteresis characteristic in which the threshold value of the light intensity that changes from the off state to the on state when the light intensity is adjusted from the weak state to the strong value shifts from the threshold value that changes from the on state to the off state when the light intensity is adjusted from the strong state to the weak state. .

  As a result, if the initial value of the light intensity is set in the middle of the two shifted thresholds, the light is shifted from the OFF state to the ON state by adding light having an intensity exceeding a certain limit, and the intensity is returned to the initial value. The on state can be maintained. As a result, this configuration can be used as a simple optical memory.

  Furthermore, if the resonator of this filter has two types of resonance frequencies, more complicated signal processing becomes possible. That is, by controlling the refractive index of the resonator with one light, the other resonance state can be controlled. That is, an all-optical switch or an optical memory that switches on and off the resonance state of the signal light with the control light can be realized.

There are Non-Patent Documents 1 and 2 as documents relating to optical switches and optical memories using ring resonators, and Non-Patent Documents 3 to 10 as documents relating to optical switches and optical memories using photonic crystals.
OPTICS LETTERS Vol. 29, no. 20, pp. 2387, 2004 NATURE Vol. 431, pp. 1081,2004 2004 Spring Society Annual Meeting Proceedings 29p-M-13 2004 Proceedings of the Spring Society of Japan 29p-M-16 Proceedings of the 2004 Autumn Society of Japan 4a-ZC-9 2004 Autumn Meeting of the Society of Natural Sciences 4a-ZC-10 Proceedings of the 2004 Fall Society of Japan 4a-ZC-11 Proceedings of the 2004 Autumn Society of Japan 4a-ZC-1 Proceedings of the 2004 Fall Society of Japan 4a-ZC-2 2004 Autumn Society Annual Meeting Proceedings 4a-ZC-3

  In the structure shown in FIGS. 1A and 1B, signal light and control light are propagated through the same waveguide. That is, the signal line and the control line exist on the same line, and there is only one input / output line. In order to perform more complicated signal processing, it may be necessary to increase the number of control lines.

  In a configuration using a ring resonator or the like, it is well known that the number of waveguides 3 can be increased as shown in FIG. 1C. However, in a configuration using a photonic crystal, the configuration shown in FIG. As shown in the figure, in a system in which four waveguides 5, 6, 7, and 8 are coupled to one resonator 4, the condition is poor. In such a coupling system, the light that has entered the resonator 4 is distributed and output in four directions, so that the signal intensity output from one waveguide is reduced to a quarter, resulting in poor efficiency. Because it becomes.

  Further, since the above structure is configured by one resonator 2 (or 4), there is a problem that only limited functionality such as AND logic and NOT logic can be realized.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an optical logic circuit capable of performing complicated signal processing using a plurality of resonators.

The invention according to claim 1 includes a plurality of resonators,
An optical logic circuit comprising a plurality of waveguides coupled to the plurality of resonators,
Since the plurality of resonators have at least one identical resonance frequency, it is possible to perform complicated signal processing using the plurality of resonators.

The invention described in claim 2 is the optical logic circuit according to claim 1,
A first resonator having a first resonance frequency and a second resonance frequency;
A first waveguide coupled to the first resonator;
A second resonator having the first and third resonance frequencies and coupled to the first resonator in a resonance mode of the first resonance frequency;
By including the second waveguide coupled to the second resonator, it is possible to perform complicated signal processing using the first and second resonators.

The invention according to claim 3 is the optical logic circuit according to claim 2,
The first resonator is turned on by input of light having a second resonance frequency, or input of light having a first resonance frequency and light having a second resonance frequency,
The second resonator is configured to be turned on when the first resonator is turned on and light having a third resonance frequency is input.

The invention according to claim 4 is the optical logic circuit according to claim 2 or 3, wherein
The first and second resonators and the first and second waveguides are formed on a photonic crystal,
The first waveguide passes the first, second, and third resonance frequencies,
The second waveguide passes only the third resonance frequency.

The invention according to claim 5 is the optical logic circuit according to claim 1,
A first resonator having a first resonance frequency and a second resonance frequency;
A plurality of first waveguides coupled to the first resonator;
A second resonator having the first resonance frequency and the second resonance frequency;
A plurality of second waveguides coupled to the second resonator;
The first and second filter units are provided between the first and second resonators and pass through the first resonance frequency and cut off the second resonance frequency. This makes it possible to perform complicated signal processing using the resonator.

The invention according to claim 6 is the optical logic circuit according to claim 5,
The first and second resonators and the first and second waveguides and filter means are formed on a photonic crystal,
The filter means is a third waveguide having filter characteristics.

The invention according to claim 7 is the optical logic circuit according to claim 6,
A part of the plurality of first waveguides, a part of the plurality of second waveguides, and the third waveguide pass through the first resonance frequency, and the second resonance frequency. Shut off
The remainder of the plurality of first waveguides and the remainder of the plurality of second waveguides pass through the second resonance frequency and block the first resonance frequency.

The invention according to claim 8 is the optical logic circuit according to any one of claims 5 to 7,
The third waveguide is set to a waveguide length that does not cause interference of light of the first resonance frequency between the first resonator and the second resonator.

The invention according to claim 9 is the optical logic circuit according to claim 2,
The first and second resonators are ring resonators or disk resonators.

  According to the present invention, it is possible to perform complicated signal processing using a plurality of resonators.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  2 and 3 show the principle configuration of the present invention.

  In FIG. 2, ring resonators (or disk resonators) 13 and 14 are arranged adjacent to the waveguides 11 and 12, respectively, and the resonance mode of the ring resonator 13 is directly coupled to the waveguide mode of the waveguide 11. The resonance mode of the ring resonator 14 is directly coupled to the waveguide mode of the waveguide 12, and the ring resonators 13 and 14 are arranged adjacent to each other.

  In FIG. 3, a resonator 22 is disposed adjacent to the opposite ends of the waveguides 20 and 21. A resonator 25 is disposed adjacent to the opposite ends of the waveguides 23 and 24. The resonance mode of the resonator 22 is directly coupled to the waveguide modes of the waveguides 20 and 21, the resonance mode of the resonator 25 is directly coupled to the waveguide modes of the waveguides 23 and 24, and the resonators 22 and 25 are It is arranged adjacent to each other. The circuit of FIG. 3 can be composed of a photonic crystal.

  2 and 3, for the sake of simplicity, a case where two resonators and resonance modes of three types of resonance frequencies (ω1, ω2, and ω3) are used will be described. May be used. In the following, a method for succinctly configuring a circuit having a complex function based on these conditions will be described.

<Coupling the resonator directly>
Two different resonators 13, 14 or 22, 25 are designed to have one identical resonance frequency ω 1 and two different resonance frequencies ω 2, ω 3. Thereby, one optical circuit can be handled as three types of equivalent circuits at the respective resonance frequencies ω1, ω2, and ω3.

  That is, since the resonance modes of all the resonators are coupled in the first circuit, all the resonators 13, 14 or 22, 25 and the waveguides 11, 12 or 20, 21, 23, 24 have light with the resonance frequency ω1. Pass through. In the second circuit, light of the resonance frequency ω2 passes through only the upper half, that is, only the resonator 13 or 22 and the waveguide 11 or 20, 21. In the third circuit, light of the resonance frequency ω3 passes through only the lower half, that is, only the resonator 14 or 25 and the waveguide 12 or 23, 24. In FIG. 2 and FIG. 3, the portion through which light passes is shown in black.

  As a result, the first circuit operating at the same resonance frequency plays a role of mediating the independent second and third circuits at two different frequencies. That is, for example, the third circuit can be controlled by the first and second circuits. In this case, since the resonance modes of the resonators 13, 14 or 22, 25 are directly coupled, there is no problem of phase when the elements interfere with each other, and the device design is greatly simplified.

<Adding a filter function between resonators>
The same two resonators have two resonance frequencies ω1, ω2 (= ω3), and have a filter characteristic between the two resonators so that the resonance modes of the two resonators are coupled only at the resonance frequency ω1. Structure. As a result, the first circuit that operates at one resonance frequency ω1 serves to mediate the independent second circuit and third circuit that operate at the other frequency ω2. That is, for example, the third circuit can be controlled by the first circuit and the second circuit. In this case, it is necessary to consider the influence of the structure showing the filter characteristics on the inter-element interference. However, there is a manufacturing advantage in that the same resonator can be used.

<Using filter characteristics of photonic crystal waveguide>
The photonic crystal waveguide itself is a band-pass filter that can easily set the band, and the degree of freedom in setting the band is high. In other words, by utilizing this characteristic, the frequency dependence can be freely given to the coupling between the resonators and the coupling between the waveguide and the resonator, and the complicated circuit is configured more simply than the conventional optical circuit. be able to.

  For example, the circuit shown in FIG. 3 can be composed of a photonic crystal. As described with reference to FIG. 1D, the light entering the resonator 4 is distributed in four directions and output, resulting in poor efficiency. This uses the filter characteristics of a waveguide formed of a photonic crystal. This can be solved. That is, the bands of the waveguides 23 and 24 are set so that the waveguide mode of the waveguides 23 and 24 and the resonance mode of the resonator 25 are not coupled. As a result, the first, second, and third circuits all become a two-port resonant tunnel filter as shown in FIG.

<First Embodiment>
FIG. 4 shows a configuration diagram of the first embodiment of the present invention. In the figure, a resonator 32 is disposed adjacent to the opposite ends of the waveguides 30 and 31. A resonator 35 is disposed adjacent to the opposite ends of the waveguides 33 and 34. The resonance mode of the resonator 32 is directly coupled to the waveguide modes of the waveguides 30 and 31, the resonance mode of the resonator 35 is directly coupled to the waveguide modes of the waveguides 33 and 34, and the resonators 32 and 35 are It is arranged adjacent to each other. The circuit of FIG. 4 can be composed of a photonic crystal.

  Here, the resonator 32 has resonance frequencies ω1 and ω2, the resonator 35 has resonance frequencies ω1 and ω3, and the resonance mode of ω1 of the resonator 32 and the resonance mode of ω1 of the resonator 35 are strongly coupled to each other. ing. The waveguides 30 and 31 have a structure through which the resonance frequencies ω1 and ω2 pass, and the resonance frequency ω3 may or may not pass through. The waveguides 33 and 34 pass through the resonance frequency ω3 and do not pass the resonance frequency ω1, and the resonance frequency ω2 may or may not pass through.

  FIG. 5A shows a first circuit which is an equivalent circuit for the resonance frequency ω1 of the circuit of FIG. 4. In the figure, the resonators 32 and 35 shown in black and the waveguides 30 and 31 have the resonance frequency ω1. Light passes through.

  FIG. 5B shows a second circuit that is an equivalent circuit for the resonance frequency ω2 of the circuit of FIG. 4. Light in the resonance frequency ω2 is transmitted to the resonator 32 and the waveguides 30 and 31 shown in black in the drawing. Pass through.

  FIG. 5C shows a third circuit that is an equivalent circuit for the resonance frequency ω3 of the circuit of FIG. 4. Light in the resonance frequency ω3 is transmitted to the resonator 35 and the waveguides 33 and 34 shown in black in the drawing. Pass through.

  Thus, the first circuit operating at the same resonance frequency ω1 can play a role of mediating the second and third circuits independent at two different resonance frequencies ω2 and ω3. That is, for example, the third circuit can be controlled by the first and second circuits.

  Here, in the three types of resonance states, the light corresponding to each is in a bistable off state, and the light intensity when another resonance state overlaps the light in a certain resonance state is set in the bistable on state. Each light intensity and frequency are set. That is, the resonator 32 is not turned on with respect to the resonant frequency ω1 when the optical input is only the resonant frequency ω1, but is turned on with respect to the resonant frequencies ω1 and ω2 when the optical inputs of the resonant frequencies ω1 and ω2 are combined. Set.

  At this time, the resonator 32 may be turned on with respect to the resonance frequency ω2 only by inputting the resonance frequency ω2. In addition, the resonator 35 is not turned on by the optical input of only the resonance frequency ω3. When the resonators 32 and 35 are turned on with respect to the resonance frequency ω1, if the optical input of the resonance frequency ω3 is made, the resonator 35 is turned on. 35 is set to be on with respect to the resonance frequency ω3.

  The light output from the port P4 of the waveguide 34 when the light having the resonance frequencies ω1, ω2, and ω3 is incident from the port P1 of the waveguide 30 or the port P3 of the waveguide 33 at the timing shown in FIG. The optical output from the circuit will be described.

  FIG. 7 shows the bistable state (input / output state) of each equivalent circuit at each of the timings (1) to (7) shown in FIG.

  (1) Since the incident light is only the resonance frequency ω3, the resonator 35 remains off and no light is output to P4.

  (2) Since the resonator 32 is off, the light incident on the first circuit cannot reach the resonator 35, and the resonator 35 remains off. Therefore, there is no output from port P4.

  (3) The resonators 32 and 35 are turned on. However, since the first and second circuits do not include the waveguide 34, there is no output from the port P4.

  (4) Because of the bistable ON state, the resonators 32 and 35 maintain the ON state even when the second circuit is interrupted. In this state, since light is incident on the third circuit, light is output from the port P4.

  (5) The resonator 35 maintains the bistable ON state even when the first circuit is interrupted. Therefore, light is output from the port P4.

  (6) Since the resonator 35 is off, there is no output from the port P4.

  (7) Since both the resonators 32 and 35 are off, there is no output from the port P4.

  Here, the case where the input intensity capable of turning on the state of the resonator 32 only with the light having the resonance frequency ω2 is considered, but the state of the resonator 32 cannot be turned on only with the light having the resonance frequency ω2, and the resonance frequency ω1 and You may set so that it may turn on with respect to each light, when the input of (omega) 2 is combined. In this case, the situation of (3) does not change, and the state of the resonator 32 with respect to the resonance frequency ω2 in (6) is turned off.

  In any case, since the first and second circuits do not include the port P4, there is no output from the port P4 in (3) and (6), so the output from the port P4 is as shown in FIG.

  Further, the resonance frequencies ω2 and ω3 are set so as to be temporally reciprocal, so that in any setting, the third frequency immediately after the light is incident on the first and second circuits. Only the light incident on this circuit functions as an optical sequential circuit that is output from the port P4.

  The above-described features can be used as an all-optical digital circuit that synchronizes an optical digital signal sequence slightly shifted from the clock with the clock.

  As shown in FIG. 8, the data signal is incident on the first circuit from the port P1 of the waveguide 30, the inverted clock signal is incident on the second circuit from the port P1 of the waveguide 30, and the port P3 of the waveguide 33 is incident. The clock signal is incident on the third circuit. Here, it is assumed that the data signal is incident on the first circuit in a state shifted from an ideal data string (indicated by a broken line) synchronized with the clock.

  As shown in FIG. 8, the output Q from the port P4 of the waveguide 34 is a signal corresponding to an ideal data string synchronized with the clock signal. Further, since the signal output from the port P3 is reflected light of the clock signal input from the port P3, the inverted signal Q bar of the output Q is output from the port P3 when the signal is not output from the port P4.

  As described above, the circuit shown in FIG. 4 converts an input NRZ (Non Return to Zero) data signal into an RZ (Return to Zero) signal, and outputs a signal Q synchronized with the clock and its inverted signal Q bar. It becomes an all-optical digital circuit.

<Second Embodiment>
The circuit shown in FIG. 4 is composed of a photonic crystal, and its operation is confirmed by a two-dimensional FDTD (Finite Difference Time Domain Method) calculation method.

  FIG. 9 shows a configuration diagram of a second embodiment of an optical logic circuit configured in a triangular lattice air hole two-dimensional slab photonic crystal. In the figure, the same parts as those in FIG. In FIG. 9, a two-dimensional slab photonic crystal 40 is a slab 41 provided with air holes 42 in a triangular lattice shape. Here, assuming that the lattice constant a of the photonic crystal 40 is 400 nm, the air hole diameter is 0.55 a, the slab thickness is 0.5 a, and the refractive index of the medium constituting the photonic crystal is 3.2, the effective refractive index is 2.8. And

  In the photonic crystal 40, four waveguides 30, 31, 33 and 34 and two resonators 32 and 35 are arranged as shown in FIG. Each of the waveguides 30 and 31 extends in the X-axis direction. The resonator 32 extends in the ΓK axis direction inclined by −60 degrees with respect to the X axis, and the resonator 35 extends in the ΓK axis direction inclined by +60 degrees with respect to the X axis. The waveguide 33 extends in the ΓK axis direction tilted by +60 degrees with respect to the X axis, and the waveguide 34 extends in the ΓK axis direction tilted by −60 degrees with respect to the X axis. Note that the ΓK axis in the crystal coordination direction of the triangular lattice air holes is a direction connecting the centers of two adjacent air holes (the directions of the three sides of the triangular lattice).

  Here, the two resonator structures have a plurality of different point defects so as to have a plurality of different resonance frequencies, and the width W of the resonator is adjusted so as to have at least one same resonance frequency. Yes.

That is, as shown in FIG. 10A, the resonator 32 is configured by a simple five-point defect resonator from which five air holes indicated by broken lines are removed. As shown in FIG. 10B, the resonator 35 removes four air holes indicated by broken lines, and sets the width W of the air hole row adjacent to both sides of the removed air hole row to the normal width W ₀ (= a It is composed of a width-adjusted four-point defect resonator shifted to 1.02 times √3). Accordingly, the resonator 32 has a plurality of resonance frequencies indicated by a solid line I in FIG. 11, and the resonator 35 has a plurality of resonance frequencies indicated by a solid line II.

The waveguides 30 and 31 are constituted by simple line defect waveguides in which one row of air holes is removed. As shown in FIG. 10C, the waveguides 33 and 34 have one row of air holes removed, and the width W of the air hole row adjacent to both sides of the removed air hole row is set to 0.80 which is the normal width W ₀ . The width adjustment waveguide is shifted so as to be doubled.

  Accordingly, as shown in FIG. 11, the waveguides 30 and 31 have a resonance mode (= resonance frequency) M1 (= ω1) in which the modes of the resonator 32 and the resonator 35 near the wavelength of 1550 nm are coupled, and a wavelength near 1490 nm. The resonance mode M2 (= ω2) and the resonance mode M3 (= ω3) in the vicinity of the wavelength of 1460 nm are waveguides through which light resonates in independent modes. The waveguides 33 and 34 are waveguides through which only the light in the resonance mode M3 passes.

  That is, the light in the resonance mode M1 incident from the port P1 of the waveguide 30 resonates with the resonators 32 and 35 and is output from the port P2 of the waveguide 31. The light in the resonance mode M2 incident from the port P1 of the waveguide 30 resonates only with the resonator 32 and is output from the port P2 of the waveguide 31. The light of the resonance mode M3 incident from the port P3 of the waveguide 33 does not resonate with the resonator 32, so cannot reach the ports P1 and P2, resonates only with the resonator 35, and is output to the port P4 of the waveguide 34. The That is, the first, second, and third circuits shown in FIG. 5 are applied to each of the resonance modes M1, M2, and M3.

  Next, the bistable operation of the resonance modes M1 and M3 is confirmed.

The nonlinear parameter used here is χ ₃ / ε ₀ = 3.2 × 10 ⁻⁶ , and acts on the electric flux D at D = (ε ₀ ε _r + χ ₃ | E | ² ) E. Here, χ ₃ is a third-order nonlinear constant, ε ₀ is a vacuum dielectric constant, ε _r is a relative dielectric constant, and E is an electric field.

  FIG. 12 shows changes in the output optical magnetic field intensity when light having a wavelength (+1.0 nm, +1.5 nm) slightly shifted from the resonance modes M1 and M3 is incident (detuning operation) and the incident light electric field amplitude is changed. Show. Here, the input optical electric field amplitude is changed by a step function in time from 12 to 48 by 4 steps, and the solid line indicates the output magnetic field strength when the input optical electric field amplitude is gradually increased, and the broken line gradually increases. The output magnetic field strength when the input optical electric field amplitude is reduced is shown superimposed on the black signal with the time axis reversed. There is a difference between the solid line and broken line signals, and hysteresis characteristics, that is, a bistable phenomenon can be confirmed.

  In this embodiment, the optical circuit is operated with a detuning of 1.5 nm and an input electric field amplitude of 20. That is, the initial state is set to off for the resonance mode M1 and M3 light (both the resonators 32 and 35 are off), and the resonance mode M2 light (electric field amplitude of about 50) is incident to turn on the resonator 32. Transition to the state. As a result, the light in the resonance mode M1 can enter the resonator 35, the resonator 35 is also turned on, and the light in the resonance mode M3 incident from the port P3 is output from the port P4.

  FIG. 13 shows the calculation result of the operation shown in FIG. 8 using the above nonlinear parameters. In FIG. 13, an output Q from the port P4 is a signal corresponding to an ideal data string synchronized with the clock signal incident from the port P3. Further, since the signal output from the port P3 is reflected light of the clock signal input from the port P3, the inverted signal Q bar of Q is output from the port P3 when no signal is output to the port P4.

FIG. 14 shows the time response of the pulse output from the port P4. The solid line indicates the case where the optical Kerr effect which is a nonlinear optical effect is not present (χ ₃ / ε ₀ = 0), and the broken line indicates the case where the optical Kerr effect is present (χ ₃ / ε ₀ = 3.2 × 10 ⁻⁶ ). . Here, in order to match the scales of the solid line and the broken line, the signal intensity when there is no optical Kerr effect is displayed multiplied by 0.425.

  Since the Q value of the resonator 32 is about 4000, the pulse fall time is about 6 ps when there is no optical Kerr effect. When the optical Kerr effect is present, the pulse rise and fall times are less than this, indicating that the optical digital circuit can operate at a high speed of 100 Gbps or more.

<Third Embodiment>
In the first and second embodiments, a method of directly coupling the resonance modes of the resonators is used. However, if the waveguide length L connecting the resonators can be optimized, FIGS. 15A and 15B are used. As shown in FIG. 5, a structure in which resonators are connected by a waveguide is also an effective circuit configuration.

  In FIG. 15A, the resonance mode of the resonator 53 is coupled to the waveguide mode of the waveguides 51 and 52, and the waveguide mode of the waveguides 54 and 55 is coupled to the resonance mode of the resonator 53. , 55 are coupled to the resonance mode of the resonator 56, and the waveguide modes of the waveguides 57, 58 are coupled to the resonance mode of the resonator 56. The waveguide length L between the resonators 53 and 56 is set to a length that does not cause attenuation due to interference of light having the same resonance frequency between the resonators 53 and 56.

  In FIG. 15B, the resonance mode of the resonator 63 is coupled to the waveguide mode of the waveguides 61 and 62, and the waveguide mode of the waveguides 64 and 65 is coupled to the resonance mode of the resonator 63. , 67 are coupled to the resonance mode of the resonator 66, and the waveguide modes of the waveguides 68, 69 are coupled to the resonance mode of the resonator 66. The waveguide length L between the resonators 63 and 66 is set to a length that does not cause attenuation due to interference of light of the same resonance frequency between the resonators 53 and 56. 15A and 15B show a configuration using a photonic crystal.

  The logic circuit illustrated in FIG. 15B includes one type of resonator and two types of waveguides. Here, the resonators 63 and 66 have two resonance frequencies ω1 and ω2, and the structures of the two types of waveguides are adjusted so that only light having one resonance frequency can pass therethrough.

  Based on this condition, three types of equivalent circuits of the circuit of FIG. 15B are shown as first, second, and third circuits in FIGS. 16A, 16B, and 16C. In FIG. 16, the portion through which light passes is shown in black. Here, the first circuit and the second and third circuits are equivalent circuits for different resonance frequencies.

  The first circuit shown in FIG. 16A is the same waveguide (passes the resonance frequency ω1) through the waveguide 65 connecting the resonators 63 and 66, the waveguide 61 of the port P1, and the waveguide 69 of the port P2. Is used, and light incident from the port P1 is output only from the port P2.

  The second and third circuits shown in FIGS. 16B and 16C operate at the same resonance frequency ω2, but the light having the resonance frequency ω2 cannot propagate through the waveguide 65 that connects the resonators 63 and 66. The light input from the port P5 of the waveguide 62 is output only from the port P6 of the waveguide 64, and the light input from the port P3 of the waveguide 67 is output only from the port P4 of the waveguide 68. is there.

  That is, it can be seen that the first circuit operating at one resonance frequency ω1 plays a role of mediating the second and third circuits independent from each other operating at the other resonance frequency ω2. That is, for example, the third circuit can be controlled by the first and second circuits.

  With this configuration, an operation equivalent to that of the first embodiment is possible, and the third embodiment has an advantage in manufacturing in that the same resonator can be used as the resonators 63 and 66.

<Fourth embodiment>
When the logic circuits of the first and second embodiments based on the photonic crystal are configured by combining a classic waveguide and a ring resonator (or a disk resonator), the configuration shown in FIG. 17 is obtained.

  In FIG. 17, ring resonators (or disk resonators) 73 and 74 are disposed adjacent to the waveguides 71 and 72, respectively, and the resonance mode of the ring resonator 73 is directly coupled to the waveguide mode of the waveguide 71. The resonance mode of the ring resonator 74 is directly coupled to the waveguide mode of the waveguide 72, and the ring resonators 73 and 74 are disposed adjacent to each other.

  Here, the resonator 73 has resonance frequencies ω1 and ω2, the resonator 74 has resonance frequencies ω1 and ω3, and the resonance mode of ω1 of the resonator 73 and the resonance mode of ω1 of the resonator 74 are strongly coupled to each other. ing. The waveguides 71 and 72 have a structure that allows the resonance frequencies ω1, ω2, and ω3 to pass therethrough.

  In this case, the filter characteristics unique to the photonic crystal waveguide cannot be used. In addition, due to the characteristics of the coupled system of the ring resonator and the waveguide, in the system where one waveguide and the ring resonator are coupled, the input light is input regardless of whether it resonates with the ring resonator or not. Output from the port on the opposite side of the port. However, the phase of the output light is shifted by π when it resonates and when it does not resonate.

  On the other hand, in the case of a structure in which a ring resonator is sandwiched between two waveguides, when there is no resonance, the input light is output from the opposite side of the same waveguide, and when it resonates, Output from one end. Three types of equivalent circuits of the circuit of FIG. 17 are shown as first, second, and third circuits in FIGS. 18 (A), (B), and (C). In FIG. 18, the portion through which light passes is shown in black.

  In the first circuit shown in FIG. 18A, when the ring resonators 73 and 74 are on, the light input from the port P 1 of the waveguide 71 is output from the port P 4 of the waveguide 72, and the ring resonator 73. , 74 are output from the port P2 of the waveguide 71 when they are off.

  The second circuit shown in FIG. 18B outputs light input from the port P1 of the waveguide 71 from the port P2 of the waveguide 71 regardless of whether the resonator 73 is on or off. However, the phase of the output light when the resonator 73 is on is shifted by π compared to when it is off.

  The third circuit shown in FIG. 18C outputs light input from the port P3 of the waveguide 72 from the port P4 of the waveguide 72 regardless of whether the resonator 74 is on or off. However, the phase of the output light when the resonator 74 is on is shifted by π compared to when it is off.

  Thereby, the circuit operation shown in FIG. 8 is rewritten as shown in FIG. In FIG. 19, unlike FIG. 8, the output Q, its inverted signal Q bar, and a part of the data signal are output from the port P4. Therefore, in order to obtain the same result as the output from the port P4 in the first and second embodiments, it is necessary to add the following elements.

  First, utilizing the fact that the wavelengths of the output Q and its inverted signal Q bar and the data signal are different, a wavelength filter is connected to the subsequent stage to separate them. Next, using the fact that the phase generated while the light input from the port P3 is output from the port P4 is shifted by π between the output Q and its inverted signal Q bar, the input light to the port P3 is used. And an output light interference system from the port P4 are added to selectively extract the output Q or the inverted signal Q bar. Alternatively, as described in Non-Patent Document 1, by setting the Q value of the resonator and the optical loss in the resonator, it is set not to output light when resonating, and the signal of output Q is not output. You can also.

  If the difference in phase between the output Q and the inverted signal Q bar is used, more complicated calculation can be performed. For example, when the input from the port P3 is composed of pulses with phase information maintained with respect to the time axis, interference with the output Q is intensified and inverted by causing interference with the continuous light CW of the same frequency. Interference with the signal Q bar can be weakened together.

  If continuous light is used as the bias light of the bistable switch, the state of the bistable switch is bistable on with the light when strengthening, and bistable off with the light when weakening, the same time width as DATA synchronized to the clock Can be extracted. That is, an NRZ data signal slightly deviated from the clock can be corrected to an NRZ data signal synchronized with the clock.

  Thus, simple optical functional elements can be easily and efficiently connected, and a more complex optical logic circuit can be configured. Thereby, it is possible to provide an optical circuit that temporarily stores an optical pulse train and enables digital signal processing. Further, it is possible to provide an optical logic circuit that exhibits different output characteristics depending on the order of signals input from each port with respect to the optical pulse signal train.

  The resonators 32, 63, 73 correspond to the first resonator described in the claims, the waveguides 30, 31, 61, 62, 64, 71 correspond to the first waveguide, and the resonators 35, 66 and 74 correspond to the second resonator, the waveguides 33, 34, 67 to 69 and 72 correspond to the second waveguide, and the waveguide 65 corresponds to the third waveguide.

It is a block diagram of an example of the coupling system of a resonator and a waveguide. It is a principle block diagram of this invention. It is a principle block diagram of this invention. It is a block diagram of 1st Embodiment of this invention. FIG. 5 is an equivalent circuit diagram of the circuit of FIG. 4. It is a figure which shows the timing of the light input and light output of each resonance frequency. It is a figure which shows the bistable state of each equivalent circuit in each timing. FIG. 5 is a diagram for explaining the circuit operation of FIG. 4. It is a block diagram of 2nd Embodiment of the optical logic circuit comprised in the triangular lattice air hole two-dimensional slab photonic crystal. FIG. 10 is a configuration diagram of the resonator and the waveguide of FIG. 9. It is a figure which shows the wavelength spectrum of a resonator. It is a figure which shows the change of output optical magnetic field intensity when changing incident light electric field amplitude. It is a figure which shows the calculation result of the operation | movement shown in FIG. It is a figure which shows the time response of the pulse output from port P4. It is a block diagram of the logic circuit of the structure where the resonator was connected by the waveguide. FIG. 16 is an equivalent circuit diagram of the logic circuit shown in FIG. It is a block diagram of the logic circuit comprised by a waveguide and a ring resonator. FIG. 18 is an equivalent circuit diagram of the circuit shown in FIG. 17. FIG. 18 is a diagram for explaining the circuit operation of FIG. 17.

Explanation of symbols

30, 31, 33, 34, 61, 62, 64 to 67, 68, 69, 71, 72 Waveguide 32, 35, 63, 66 Resonator 40 Photonic crystal 41 Slab 42 Air hole 71, 72 Ring resonator

Claims (9)

A plurality of resonators;
An optical logic circuit comprising a plurality of waveguides coupled to the plurality of resonators,
The plurality of resonators have at least one identical resonance frequency. The optical logic circuit according to claim 1,
A first resonator having a first resonance frequency and a second resonance frequency;
A first waveguide coupled to the first resonator;
A second resonator having the first and third resonance frequencies and coupled to the first resonator in a resonance mode of the first resonance frequency;
An optical logic circuit comprising a second waveguide coupled to the second resonator. The optical logic circuit according to claim 2, wherein
The first resonator is turned on by input of light having a second resonance frequency, or input of light having a first resonance frequency and light having a second resonance frequency,
The optical logic circuit, wherein the second resonator is configured to be turned on when the first resonator is turned on and light having a third resonance frequency is input. The optical logic circuit according to claim 2 or 3,
The first and second resonators and the first and second waveguides are formed on a photonic crystal,
The first waveguide passes the first, second, and third resonance frequencies,
The optical logic circuit, wherein the second waveguide passes only the third resonance frequency. The optical logic circuit according to claim 1,
A first resonator having a first resonance frequency and a second resonance frequency;
A plurality of first waveguides coupled to the first resonator;
A second resonator having the first resonance frequency and the second resonance frequency;
A plurality of second waveguides coupled to the second resonator;
An optical logic circuit comprising filter means which is provided between the first and second resonators and which passes the first resonance frequency and cuts off the second resonance frequency. . The optical logic circuit according to claim 5, wherein
The first and second resonators and the first and second waveguides and filter means are formed on a photonic crystal,
The optical logic circuit, wherein the filter means is a third waveguide having a filter characteristic. The optical logic circuit according to claim 6, wherein
A part of the plurality of first waveguides, a part of the plurality of second waveguides, and the third waveguide pass through the first resonance frequency, and the second resonance frequency. Shut off
The remainder of the plurality of first waveguides and the remainder of the plurality of second waveguides pass through the second resonance frequency and block the first resonance frequency. Logic circuit. The optical logic circuit according to any one of claims 5 to 7,
The third waveguide is set to a waveguide length that does not cause interference of light of the first resonance frequency between the first resonator and the second resonator. Optical logic circuit. The optical logic circuit according to claim 2, wherein
The optical logic circuit, wherein the first and second resonators are ring resonators or disk resonators.