JP4449652B2 - Optical switch circuit - Google Patents

Description

  The present invention relates to an optical switch circuit, and more particularly to an optical switch circuit whose optical output depends not only on the current optical input but also on the past optical input history.

  In a planar optical circuit using a two-dimensional photonic crystal as a platform, it has been suggested that the coupling system of a waveguide and a resonator can realize functionality in an area of several wavelengths. It is a remarkable optical circuit configuration.

  As shown in FIG. 1, a structure in which one waveguide 2 is provided on a two-dimensional photonic crystal 1 and one resonator 3 is disposed adjacent to the waveguide 2 is a signal light at the resonance wavelength of the resonator. Is a drop filter for taking out the signal from the planar circuit (see, for example, Non-Patent Document 1). In addition, an optical switch circuit that controls the signal light with the control light is configured by directly irradiating the two-dimensional photonic crystal with external light (control light) having a wavelength that causes light absorption to manipulate the resonance wavelength of the resonator. (For example, refer nonpatent literature 2).

In Non-Patent Document 3, centering on a single point defect on the photonic crystal, the six air holes adjacent to the single point defect are radially narrowed away from the single point defect, and the diameter is increased. It is described that the resonator is configured to be small, and Non-Patent Document 4 describes that the Q value of the resonator is controlled. Non-Patent Documents 5 and 6 describe the structure of a waveguide.
S. Noda, et al Nature 407, 608 (2000) W. Kunishi, et al International Symposium on photonic and electromagnetic crystal structures VPECS-V, 243 (2004) H. Y. Ryu, et al Applied Physics Letters. 83, 4294 (2003) Miki et al., 2003 Spring Japan Society of Applied Physics, 3rd volume, 1138 (2003) 29a-YN-7 A. Shinya, et al processings of SPIE, 5000, 104, (2003) A. Shinya, et al processings of SPIE, 5000, 125, (2003)

  In the structure described in Non-Patent Document 1, the signal light is extracted out of the plane from the planar circuit. Further, the optical control optical switch circuit described in Non-Patent Document 2 also performs switching of light extraction from the planar circuit to the out-of-plane, and it is necessary to irradiate the control light from the outside of the planar circuit. -There was a problem that high integration was difficult.

  The present invention has been made in view of the above points, and provides an optical switch circuit capable of signal processing within a two-dimensional photonic crystal plane, enabling high integration, and operating with low optical power. For the purpose.

FIG. 2 shows a first principle configuration diagram of the present invention. According to the first aspect of the present invention, a pair of waveguides (5, 6) configured on the two-dimensional photonic crystal (4) and a photo disposed between the pair of waveguides (5, 6) are provided. A resonant tunneling filter composed of a nicked crystal resonator (7);
An optical switch circuit that inputs signal light and control light that resonates with the resonator (7) from one of the pair of waveguides (5, 6) and extracts the signal light from the other, and modulates the signal light with the control light. And
The resonant tunneling filter has first and second resonant wavelengths;
Assigning the first resonance wavelength to the signal light;
By assigning the second resonance wavelength to the control light ,
The signal light and control light Ri Do allow various signal processing can be highly integrated in two dimensions propagates photonic crystal plane in the two-dimensional photonic crystal surface, nonlinear required optical switching with a low optical power can be generated a phenomenon, Ru can operate at low optical power.

FIG. 3 shows a second principle configuration diagram of the present invention. According to a second aspect of the present invention, there is provided a first pair of waveguides (11, 12, 13, 14) formed on a two-dimensional photonic crystal (10), and the first pair of waveguides. A resonant tunneling filter comprising a photonic crystal resonator (15) disposed between waveguides and disposed between the second pair of waveguides;
The signal light that resonates with the resonator (15) is input from one of the first pair of waveguides (11, 12) and extracted from the other, and the control light that resonates with the resonator (15) is An optical switch circuit that inputs from one of the second pair of waveguides (13, 14) and takes out from the other, and modulates the signal light with the control light ,
The resonant tunneling filter has first and second resonant wavelengths;
Assigning the first resonance wavelength to the signal light;
Assigning the second resonance wavelength to the control light;
The resonator has at least first and second resonance modes,
By matching the symmetry of the field shape of each resonance mode with the symmetry of the field shape of the waveguide mode of the first and second pair of waveguides, the signal light is transmitted to the first pair of waveguides. And propagating the control light to the second pair of waveguides ,
Signal light and control light propagate in the two-dimensional photonic crystal plane, and various signal processing is possible in the two-dimensional photonic crystal plane, enabling high integration, and signal light and control light propagate in separate waveguides. Can generate nonlinear phenomena necessary for optical switching with low optical power, can operate with low optical power, and can realize propagation of signal light and control light in separate waveguides The

The invention according to claim 3 is the optical switch circuit according to claim 2 ,
According to the coincidence between the symmetry with respect to the ΓK axis which is the crystal coordination direction of the field shape of the first resonance mode and the symmetry of the field shape with respect to the ΓK axis of the waveguide mode of the first pair of waveguides, Propagating the signal light to the first pair of waveguides by coupling a resonator and the first pair of waveguides,
Due to the mismatch between the symmetry of the field shape of the first resonance mode with respect to the ΓK axis and the symmetry of the field shape of the waveguide mode of the second pair of waveguides with respect to the ΓK axis, By not propagating to a pair of waveguides,
It is possible to prevent the signal light from propagating through the first pair of waveguides and not from the second pair of waveguides.

The invention according to claim 4 is the optical switch circuit according to claim 3 ,
According to the coincidence between the symmetry of the field shape of the second resonance mode with respect to the ΓM axis orthogonal to the ΓK axis and the symmetry of the field shape of the waveguide mode of the second pair of waveguides with respect to the ΓM axis, And the control light is propagated to the second pair of waveguides by coupling the second pair of waveguides to the second pair of waveguides,
Due to a mismatch between the symmetry of the field shape of the second resonance mode with respect to the ΓM axis and the symmetry of the field shape of the waveguide mode of the first pair of waveguides with respect to the ΓM axis, From not propagating to a pair of waveguides,
It is possible to prevent the control light from propagating through the second pair of waveguides and not from the first pair of waveguides.

The invention according to claim 5 is the optical switch circuit according to claim 2 ,
By coupling the resonance frequency of the first resonance mode with the band of the waveguide mode of the first pair of waveguides, the resonator and the first pair of waveguides are coupled to transmit the signal light Propagating to a first pair of waveguides;
The signal light is not propagated to the second pair of waveguides due to a mismatch between the resonance frequency of the first resonance mode and the band of the waveguide modes of the second pair of waveguides.
It is possible to prevent the signal light from propagating through the first pair of waveguides and not from the second pair of waveguides.

The invention according to claim 6 is the optical switch circuit according to claim 5 ,
By combining the resonance frequency of the second resonance mode and the band of the waveguide mode of the second pair of waveguides, the resonator and the second pair of waveguides are coupled to transmit the control light. Propagating to a second pair of waveguides;
Due to the mismatch between the resonance frequency of the second resonance mode and the band of the waveguide mode of the first pair of waveguides, the control light is not propagated to the first pair of waveguides.
It is possible to prevent the control light from propagating through the second pair of waveguides and not from the first pair of waveguides.

The invention according to claim 7 is the optical switch circuit according to any one of claims 2 to 6 ,
Since the resonator has the hexapole mode in the photonic band gap, the hexapole mode can be used as the second resonance mode.

  According to the present invention, signal processing can be performed within the two-dimensional photonic crystal plane, high integration can be achieved, and operation can be performed with low optical power.

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

  FIG. 4 shows a block diagram of the first embodiment of the optical switch circuit of the present invention. This embodiment has a circuit configuration corresponding to FIG. In FIG. 4, a triangular lattice air hole two-dimensional photonic crystal 20 is obtained by providing a triangular lattice air hole 24 in a silicon slab 22 having an air bridge structure. For example, a lattice constant a = 420 nm and an air hole radius of 0. 275a and slab thickness 0.5a.

  Here, the ΓK axis in the crystal coordination direction of the air holes 24 in the triangular lattice shape is a direction connecting the centers of two adjacent air holes, and the three sides of the triangular lattice correspond to the ΓK axis. The ΓM axis is perpendicular to the straight line connecting the centers of two adjacent air holes (ΓK axis) and is directed toward the center of the shortest air hole.

  The waveguides 26 and 28 are configured by removing the air holes 24 of the photonic crystal in the X-axis direction overlapping the ΓK axis, and the waveguide 28 is disposed on an extension line of the waveguide 26.

  The resonator 30 is arranged so that the end portion is located at a position that passes through several potential barriers (several photonic crystal cycles) in the ΓK axis direction from the opposing end portions of the waveguides 26 and 28. The resonator 30 is configured so that two air holes (shown by black circles) 32 adjacent to both ends in the X-axis direction of the three-point defect (deletion of three air holes) extending in the X-axis direction are separated from the three-point defect. The width is reduced in the X-axis direction and the diameter is reduced (see Non-Patent Document 4).

  That is, the resonator 30 is arranged so as to divide one waveguide into two waveguides 26 and 28, and this structure is a circuit configuration called a resonant tunnel filter, and propagates through one waveguide 26. The light can pass through the resonator 30 and propagate through the other waveguide 28 only when the wavelength of the incident light matches the resonance wavelength of the resonator 30. The resonator 30 is a photonic crystal resonator having an extremely small mode volume, and can generate a nonlinear phenomenon necessary for optical switching with a low optical power by extremely increasing the light density of the control light.

  This non-linear phenomenon fluctuates the refractive index of the region inside and around the resonator 30 and fluctuates the resonance wavelength of the resonator 30. That is, the difference between the wavelength of the signal light and the resonance wavelength of the resonator 30 can be adjusted by the light intensity of the control light. Thereby, when the signal light passes through the resonant tunneling filter (ON) and when it does not pass (OFF), the change can be adjusted by the light intensity of the control light.

  The resonator 30 of this resonant tunneling filter has two resonance modes in one structure. The change in the refractive index due to the nonlinear phenomenon generated for one resonance mode changes not only the resonance wavelength of the resonance mode but also the resonance wavelength of the other resonance mode. That is, if this mechanism is used, the signal light can be modulated with the control light.

  FIG. 5A shows a transmission spectrum of one waveguide (waveguide mode) that is not divided and a transmission spectrum of the resonant tunneling filter shown in FIG. In FIG. 5A, two resonance tunnel signals of resonance mode 1 and resonance mode 2 can be observed within the observation band of the waveguide mode (1500 to 1580 nm). In the present invention, resonance mode 1 is assigned to control light, and resonance mode 2 is assigned to signal light.

  In FIG. 5B, the transmission spectrum of the signal light when high power control light is input (ON) is indicated by a solid line, and the transmission spectrum of the signal light when not input (OFF) is indicated by a broken line. By turning on the control light, the signal light spectrum is shifted to the long wavelength side.

  In the case of silicon which is the material of the photonic crystal 20, the shift of the signal light spectrum to the longer wavelength side means thermal nonlinearity. Conventionally, since silicon is transparent in the observation wavelength band, the generation of heat by light should be extremely small. However, in this structure, by using the photonic crystal resonator 30, the energy density is extremely small in a very small space region. Since high light is confined, the nonlinear phenomenon of heat can be easily generated.

  Further, by setting the wavelength of the signal light to λ1 and λ2 shown in FIG. 5B, the logical operation of the signal light and the control light can be performed as shown in FIG. That is, when the wavelength of the signal light is λ1, the output of the signal light shown in FIG. 6B is reduced by turning on the control light shown in FIG. 6A, so that a NOT circuit is configured. On the other hand, when the wavelength of the signal light is λ2, the control light shown in FIG. 6A is turned on, and the output of the signal light shown in FIG. In this way, an optical switch circuit of light control can be realized by using two resonance modes.

  Thus, in the above embodiment, since the signal light and the control light propagate in the two-dimensional circuit plane, various signal processing can be performed in the two-dimensional plane, and high integration is possible. Further, by using a photonic crystal resonator having two resonance modes, it is possible to generate a nonlinear phenomenon necessary for optical switching with low optical power, and to operate with low optical power.

  By the way, in the circuit configuration of FIG. 4, since signal light and control light need to propagate through the same waveguide, there is a possibility that a complicated circuit cannot be configured in the future. Therefore, a method of separating the signal light and the control light using the symmetry of the field shape of the resonance mode of the resonator will be described.

  FIG. 7 shows a configuration diagram of a second embodiment of the optical switch circuit of the present invention. This embodiment has a circuit configuration corresponding to FIG. In FIG. 7, a triangular lattice air hole two-dimensional photonic crystal 40 is a silicon slab 42 having an air bridge structure provided with a triangular lattice air hole 44. For example, the lattice constant a = 420 nm and the air hole radius 0. 275a and slab thickness 0.5a.

  The waveguides 46 and 48 are configured by removing the air holes 44 of the photonic crystal in the Y-axis direction overlapping the ΓK axis, and the waveguide 48 is disposed on an extension line of the waveguide 46.

  A resonator 50 is disposed between the waveguides 46 and 48. The resonator 50 is centered on a single point defect (defect of one air hole), and the six air holes (indicated by black circles) 52 adjacent to the single point defect are radially shifted away from the single point defect. In addition, the diameter is reduced (see Non-Patent Documents 3 and 4).

  In addition, waveguides 54 and 56 are arranged so that the end portions are located at positions through several rows of air holes on both sides in the X-axis direction overlapping the ΓM axis with the resonator 50 as the center. The waveguide 54 is configured by removing the air holes 44 of the photonic crystal from the end close to the resonator 50 in the ΓK axis direction inclined by −30 degrees with respect to the X axis, and the waveguide 56 is configured by the resonator 50. The air holes 44 of the photonic crystal are removed in the ΓK-axis direction tilted by −30 degrees with respect to the X-axis from the end close to the X-axis.

  Furthermore, the waveguides 46, 48, 54, and 56 remove the air hole row in a line shape as shown in FIG. 20A, and are adjacent to the removed air hole row as shown in FIG. 20B. The air hole row is shifted so that the waveguide width becomes narrower (W <Wo), and the shape of the air hole row outside the shifted air hole row is further shifted as shown in FIG. (See Non-Patent Documents 5 and 6). In FIG. 20, black circles represent air holes.

  FIG. 21 shows the correspondence between the propagation mode band of the resonator 50 of FIG. 7 and the resonance frequency (resonance wavelength). In this embodiment, the waveguide width W is 0.937 Wo (Wo is the distance between the centers of the air hole rows adjacent to both sides of the removed air hole row). Thus, a waveguide having a waveguide mode that is positively symmetric with respect to the ΓK axis is configured in a band in which the dipole mode and the hexapole mode exist by manipulating the waveguide width.

  The waveguides 46 and 48 are signal lines that guide the signal light, and the waveguides 54 and 56 are control lines that guide the control light. The resonator 50 is located at a point where the signal line and the control line intersect. Is arranged.

  The resonator 50 has two resonance modes, which are assigned to signal light and control light, respectively. The refractive index variation due to the nonlinear phenomenon that occurs with respect to the resonance mode of the control light changes not only the resonance wavelength of the resonance mode of the control light but also the resonance wavelength of the resonance mode of the signal light, and modulates the signal light with the control light. be able to.

  Furthermore, although signal light and control light are mixed in the resonator 50, the signal light cannot propagate through the control line, and the control light cannot propagate through the signal line. This will be described. The resonator 50 has a hexapole mode in the photonic band gap, and has a plurality of resonance mode field shapes as shown in FIGS. That is, a dipole mode, a quadrupole mode, and a hexapole mode. In FIGS. 8 to 10, the resonance modes in the vicinity of the resonator 50 are represented by symbols and shades (the darker the stronger).

Among the dipole modes shown in FIG. 8, the one shown on the right side is bilaterally symmetrical, that is, positively symmetric with respect to the ΓK axis. Of the quadrupole modes shown in FIG. 9, the one shown on the right side is symmetrical with respect to the ΓK axis, that is, positively symmetric. The hexapole mode shown in FIG. 10 is asymmetrical or anti-symmetric with respect to the ΓK axis, and is symmetric or positively symmetrical with respect to the ΓM axis. A case having an even function field shape with respect to a symmetric axis such as a ΓK axis or a ΓM axis is defined as positive symmetry, and a case having an odd function field shape with respect to the symmetric axis is defined as antisymmetric. For example, in the dipole mode shown on the right side of FIG. 8, it can be seen that the signs coincide on the left and right sides of the ΓK axis and are positively symmetrical with respect to the ΓK axis. In addition, in the hexapole mode shown in FIG. 10, it can be seen that the signs coincide on the left and right sides of the ΓM axis and are positively symmetric with respect to the ΓM axis.

  FIG. 11 shows field shapes of the dipole mode, hexapole mode, and waveguide mode of the waveguide 46 with respect to the ΓK axis, and FIG. 12 shows the dipole mode of the resonator 50 with respect to the ΓM axis. The field shapes of the multipole mode and the waveguide mode of the waveguide 54 are shown.

  The double pole handled here is the resonance mode on the right side of FIG. Since the triangular lattice air hole two-dimensional photonic crystal has three-fold symmetry, this dipole mode is equivalent even if rotated by 120 degrees and 240 degrees, and originally three types of resonance modes overlap the same resonance frequency. ing. However, since the symmetry is lost due to the coupling with the waveguide, these resonance frequencies are split and the overlap (degeneration) can be solved. Alternatively, the degeneracy can be solved by shifting the structure of the resonator from the three-fold symmetry. Therefore, attention is paid only to a mode symmetric with respect to the Y-axis, and this is shown as a double pole in FIGS. 11A and 12A. There is no such degeneracy in the hexapole.

  11 and 12, the field spreads and attenuates while vibrating in the directions indicated by the solid line arrows and the broken line arrows. Further, the solid line arrows and the broken line arrows are 180 degrees out of phase with each other.

  When coupling the modes, the mutual coupling is the strongest when the arrows have the same slope, and the mutual coupling is the weakest when they are orthogonal.

  The dipole mode shown in FIG. 11A and the waveguide mode of the waveguide 46 (or 48) shown in FIG. 11C are positively symmetrical with respect to the ΓK axis, and the hexapole shown in FIG. Since the mode is antisymmetric with respect to the ΓK axis, the dipole mode of the resonator 50 is coupled to the waveguide modes of the waveguides 46 and 48, and the hexapole mode of the resonator 50 cannot be coupled.

  In addition, the hexapole mode shown in FIG. 12B and the waveguide mode of the waveguide 54 (or 56) shown in FIG. 12C are positively symmetric with respect to the ΓM axis, and are shown in FIG. 12A. Since the multipole mode is antisymmetric with respect to the ΓM axis, the hexapole mode of the resonator 50 is coupled to the waveguide modes of the waveguides 54 and 56, and the dipole mode of the resonator 50 cannot be coupled.

  For this reason, in FIG. 7, the signal light input from the outside to the signal line of the waveguide 46 passes through the resonator 50 and is output to the outside through the waveguide 48. The control light input from the outside to the control line of the waveguide 54 passes through the resonator 50 and is output to the outside through the waveguide 56.

  FIG. 13 shows the spectrum of the resonator 50 when light having a relatively wide wavelength band is introduced from the signal line (waveguides 46 and 48) and the control line (waveguides 54 and 56) in FIG. The calculation result is indicated by a broken line, and the calculation result of the spectrum output from the signal line (waveguide 48) is indicated by a solid line. Here, two modes of a dipole and a hexapole are excited in the resonator 50, and the dipole mode is output to the signal line, but the hexapole mode is output to the signal line. I understand that there is no.

Thus, by considering the symmetry with respect to each of the ΓK axis and the ΓM axis , the waveguide mode can be selectively coupled to an arbitrary resonator mode.

  In the embodiment shown in FIG. 7, as shown in FIG. 14A, the resonator 50 is disposed between the two waveguides 46 and 48 provided on the ΓK axis, and the dipole mode of the resonator 50 is changed. The waveguide modes of the waveguides 46 and 48 are coupled. In addition to this, as shown in FIG. 14B, the field extends from the opposing ends of the two waveguides 46 and 48 provided on the ΓK axis (inclined ± 30 degrees with respect to the ΓK axis direction). It is possible to arrange the resonator 50 at the intersection position (in the ΓM axis direction) and couple the dipole mode of the resonator 50 with the waveguide modes of the waveguides 46 and 48. Further, as shown in FIG. 14C, the resonator 50 is arranged in the direction (ΓM axis direction) in which the field extends from the end of the waveguide 46 provided on the ΓK axis, and the field extends from the resonator 50. It is possible to couple the dipole mode of the resonator 50 with the waveguide modes of the waveguides 46 and 48 by arranging the end of the waveguide 48 in the (ΓM axis direction) and providing the waveguide 48 on the ΓK axis. It is.

  Further, as shown in FIG. 15A, resonance occurs at the intersection point in the direction (ΓM axis direction) in which the field extends from the end portions of the waveguides 46 and 48 provided on the ΓK axis in parallel and spaced apart in the X axis direction. It is possible to place the resonator 50 and couple the dipole mode of the resonator 50 with the waveguide modes of the waveguides 46 and 48. . Further, as shown in FIG. 15B, the resonator extends in the direction (ΓM axis direction) in which the field extends from the end of the waveguide 46 provided on the ΓK axis inclined by −30 degrees with respect to the X axis (ΓM axis). 50, the end of the waveguide 48 is arranged in the direction in which the field extends from the resonator 50 (ΓM axis direction), the waveguide 48 is provided on the ΓK axis inclined +30 degrees with respect to the X axis, and the resonator 50 Can be coupled to the waveguide modes of the waveguides 46 and 48. Further, as shown in FIG. 15C, the resonator 50 is arranged in the direction (ΓM axis direction) in which the field extends from the end of the waveguide 46 provided on the ΓK axis inclined by −30 degrees with respect to the X axis. The end of the waveguide 48 is arranged in the direction in which the field extends from the resonator 50 (ΓM axis direction), and the waveguide 48 is provided on the ΓK axis inclined by −30 degrees with respect to the X axis. It is possible to couple the polar mode with the waveguide modes of the waveguides 46 and 48.

  However, the configuration shown in FIG. 14A couples only the dipole mode of the resonator 50 to the waveguide modes of the waveguides 46 and 48, whereas FIGS. 14B, 14C, and 15 show. In the configurations shown in (A), (B), and (C), not only the dipole mode of the resonator 50 but also the hexapole mode is coupled to the waveguide modes of the waveguides 46 and 48.

  On the other hand, as shown in FIG. 16A, the field extends from the opposing ends of the two waveguides 54 and 56 provided on the ΓK axis (ΓM axis inclined by ± 30 degrees with respect to the ΓK axis direction). It is possible to dispose the resonator 50 at the intersection point of the (direction) and couple the hexapole mode of the resonator 50 with the waveguide modes of the waveguides 54 and 56. Further, as shown in FIG. 16B, the resonator 50 is arranged in the direction (ΓM axis direction) in which the field extends from the end of the waveguide 54 provided on the ΓK axis, and the field extends from the resonator 50. The end of the waveguide 56 is arranged in the (ΓM axis direction) and the waveguide 56 is provided on the ΓK axis, so that the hexapole mode of the resonator 50 can be coupled with the waveguide modes of the waveguides 54 and 56. It is.

  Further, as shown in FIG. 17A, resonance occurs at the intersection point in the direction (ΓM axis direction) in which the field extends from the end portions of the waveguides 54 and 56 provided on the ΓK axis in parallel and spaced apart in the X axis direction. It is possible to place the resonator 50 and couple the hexapole mode of the resonator 50 with the waveguide modes of the waveguides 54 and 56. In addition, as shown in FIG. 17B, the resonator extends in the direction (ΓM axis direction) in which the field extends from the end of the waveguide 54 provided on the ΓK axis inclined by −30 degrees with respect to the X axis (ΓM axis). 50, the end of the waveguide 56 is arranged in the direction in which the field extends from the resonator 50 (in the ΓM axis direction), and the waveguide 56 is provided on the ΓK axis inclined +30 degrees with respect to the X axis. Can be combined with the waveguide modes of the waveguides 54 and 56. Further, as shown in FIG. 17C, the resonator 50 is arranged in the direction (ΓM axis direction) in which the field extends from the end of the waveguide 54 provided on the ΓK axis inclined by −30 degrees with respect to the X axis. The end of the waveguide 56 is arranged in the direction in which the field extends from the resonator 50 (ΓM axis direction), and the waveguide 56 is provided on the ΓK axis inclined by −30 degrees with respect to the X axis. It is possible to couple the polar mode with the waveguide modes of the waveguides 54 and 56.

  However, in the configuration shown in FIGS. 16A and 16B and FIGS. 17A, 17B, and 17C, not only the hexapole mode of the resonator 50 but also the dipole mode is introduced. It will couple | bond with the waveguide mode of the waveguides 54 and 56.

  On the other hand, in the embodiment shown in FIG. 7, as shown in FIG. 18A, the waveguides 54 and 56 are provided on the ΓK axis inclined by −30 degrees with respect to the X axis overlapping the ΓM axis. The end portions of 54 and 56 are disposed on both sides in the X-axis direction from the resonator 50, and only the hexapole mode of the resonator 50 is coupled to the waveguide modes of the waveguides 54 and 56.

  As shown in FIG. 18B, a waveguide 54 is provided on the ΓK axis inclined +30 degrees with respect to the X axis, and a waveguide 56 is provided on the ΓK axis inclined −30 degrees with respect to the X axis. The ends of the waveguides 54 and 56 are arranged so as to be located on both sides in the X-axis direction from the resonator 50, and only the hexapole mode of the resonator 50 is coupled to the waveguide modes of the waveguides 54 and 56.

  Therefore, the configuration illustrated in FIG. 14A is combined with the configuration illustrated in FIG. The configuration of FIG. 19A is the same as the configuration shown in FIG. Here, the resonator 50 is disposed between the two waveguides 46 and 48 provided on the ΓK axis, and the dipole mode of the resonator 50 is coupled to the waveguide modes of the waveguides 46 and 48. Further, waveguides 54 and 56 are provided on the ΓK axis inclined by −30 degrees with respect to the X axis overlapping the ΓM axis, and the ends of the waveguides 54 and 56 are arranged so as to be located on both sides in the X axis direction from the resonator 50. In addition, only the hexapole mode of the resonator 50 is coupled with the waveguide modes of the waveguides 54 and 56. Thereby, the signal light input to the signal line of the waveguide 46 can be taken out only to the waveguide 48 through the resonator 50, and the control light input to the control line of the waveguide 54 is guided through the resonator 50. Only the waveguide 56 can be taken out.

  Similarly, the structure illustrated in FIG. 14A is combined with the structure illustrated in FIG. 18B to form the structure illustrated in FIG. Here, the resonator 50 is disposed between the two waveguides 46 and 48 provided on the ΓK axis, and the dipole mode of the resonator 50 is coupled to the waveguide modes of the waveguides 46 and 48. A waveguide 54 is provided on the ΓK axis inclined +30 degrees with respect to the X axis, a waveguide 56 is provided on the ΓK axis inclined -30 degrees with respect to the X axis, and the ends of the waveguides 54 and 56 are connected to the resonator 50. Are arranged so as to be located on both sides in the X-axis direction, and only the hexapole mode of the resonator 50 is coupled with the waveguide modes of the waveguides 54 and 56. Thereby, the signal light input to the signal line of the waveguide 46 can be taken out only to the waveguide 48 through the resonator 50, and the control light input to the control line of the waveguide 54 is guided through the resonator 50. Only the waveguide 56 can be taken out.

  Since the resonator 30 shown in FIG. 4 has a field shape in which the number of nodes in the dipole mode is increased in the ΓK axis direction, FIGS. 14 (A) to (C) and FIGS. 15 (A) to (C). Similarly to each, the resonator 30 and the waveguides 26 and 28 can be arranged. In this case, the resonator 50 corresponds to the resonator 30, and the waveguides 46 and 48 correspond to the waveguides 26 and 28.

  Next, it is shown that a specific resonance mode and a specific waveguide can be coupled by matching / mismatching of the resonance mode and the waveguide mode band.

  FIG. 22 shows a configuration diagram of a third embodiment of the optical switch circuit of the present invention. This embodiment has a circuit configuration corresponding to FIG. In FIG. 22, a triangular lattice air hole two-dimensional photonic crystal 60 is obtained by providing a triangular lattice air hole 64 in a silicon slab 62 having an air bridge structure. For example, the lattice constant a = 400 nm and the air hole radius 0. .22a and slab thickness 0.5a.

  The waveguides 66 and 68 are configured by removing the air holes 64 of the photonic crystal in the Y-axis direction overlapping the ΓK axis, and the waveguide 68 is disposed on the extended line of the waveguide 66.

  A resonator 70 is disposed between the waveguides 66 and 68. The resonator 70 is centered on a single point defect, and the six air holes (shown by black circles) 72 adjacent to the single point defect are radially narrowed away from the single point defect, and the diameter is reduced. Is formed.

  In addition, waveguides 74 and 76 are arranged so that the end portions are located at positions where several air hole rows pass on both sides in the X-axis direction overlapping the ΓM axis with the resonator 70 as the center. The waveguide 74 is configured by removing the air holes 64 of the photonic crystal from the end close to the resonator 70 in the ΓK axis direction inclined +30 degrees with respect to the X axis, and the waveguide 76 is connected to the resonator 70. The air hole 64 of the photonic crystal is removed from the near end portion in the ΓK axis direction inclined by −30 degrees with respect to the X axis.

  Furthermore, the waveguides 66, 68, 74, and 76 remove the air hole row in a line shape as shown in FIG. 20A, and are adjacent to the removed air hole row as shown in FIG. 20B. The air hole row is shifted so that the waveguide width becomes narrower (W <Wo), and the shape of the air hole row outside the shifted air hole row is further shifted as shown in FIG. Only spread.

  The waveguides 66 and 68 are signal lines that guide the signal light, and the waveguides 74 and 76 are control lines that guide the control light. A resonator 70 is provided at a point where the signal line and the control line intersect. Has been placed. The resonator 70 has two resonance modes, which are assigned to signal light and control light, respectively.

  The refractive index variation due to the nonlinear phenomenon that occurs with respect to the resonance mode of the control light changes not only the resonance wavelength of the resonance mode of the control light but also the resonance wavelength of the resonance mode of the signal light, and modulates the signal light with the control light. be able to.

FIG. 23 shows the correspondence between the propagation mode band of the waveguide used in this circuit and the resonance mode. The waveguide width is adjusted by the method shown in FIG. By this method, the waveguide mode band of the simple line defect shown in FIG. 20A can be shifted to the high frequency side by narrowing the waveguide width, and the low frequency side can be achieved by widening the waveguide width. Can be shifted. As shown in FIG. 23, for example, when W = 0.9 Wo, the modes of positive symmetry and antisymmetric are shifted to the high frequency side. Further, when the waveguide width is narrowed (W <0.85 Wo), a new positive symmetric mode appears from the left end of the photonic band gap as W = 0.7 Wo (see Non-Patent Documents 5 and 6). ).
By utilizing these characteristics, a waveguide mode band suitable for a specific resonance mode can be set.

  The waveguide width W = 0.7 Wo is used as the signal line waveguides 66, 68, and the waveguide width W = 0.9 Wo is used as the control line waveguides 74, 76. This allows the double pole to be coupled only to the signal line and the hexapole to be coupled only to the control line. FIG. 24 shows an output light spectrum, a propagation mode band, and a resonance frequency from the signal line and the control line when the resonance mode is directly excited by a broadband light source. Thus, it is clear that the double pole is coupled only with the signal light, and the hexapole is coupled only with the control light.

  As described above, since the structure of the present invention propagates signal light and control light in a two-dimensional optical circuit based on a two-dimensional photonic crystal, various signal processing is possible in a two-dimensional plane and high integration is achieved. Is possible. Further, by using a photonic crystal resonator having two resonance modes, it is possible to operate with ultra-small size and low optical power. In addition, by considering the symmetry of the mode shape of the resonator, it is possible to combine the signal light and the control light into separate waveguides to configure a complicated circuit.

  The waveguides 46, 48, 66, and 68 correspond to the first pair of waveguides described in the claims, and the waveguides 54, 56, 74, and 76 correspond to the second pair of waveguides. The pole mode corresponds to the first resonance mode, and the hexapole mode corresponds to the second resonance mode.

It is a block diagram of an example of the conventional optical circuit. It is a 1st principle block diagram of this invention. It is a 2nd principle block diagram of this invention. It is a block diagram of 1st Embodiment of the optical switch circuit of this invention. It is a figure which shows the transmission spectrum when the transmission spectrum of a resonance tunnel filter and control light are turned ON / OFF. It is a wave form diagram which shows that signal light can be modulated with control light. It is a block diagram of 2nd Embodiment of the optical switch circuit of this invention. It is a figure which shows the field shape of the dipole mode of the resonator used in FIG. It is a figure which shows the field shape of the quadrupole mode of the resonator used in FIG. It is a figure which shows the field shape of the hexapole mode of the resonator used in FIG. It is a figure which shows the field shape of each of the dipole mode of the resonator 50 with respect to the ΓK axis, the hexapole mode, and the waveguide mode of the waveguide 46. It is a figure which shows the field shape of each of the dipole mode of the resonator 50 with respect to the ΓM axis, the hexapole mode, and the waveguide mode of the waveguide 54. It is a figure which shows the calculation result of the spectrum in a resonator when a light with a comparatively wide spectrum of a wavelength band is introduce | transduced from a signal line and a control line, and the spectrum output from a signal line. It is a figure which shows coupling | bonding with the dipole mode of the resonator 50, and the waveguide mode of the waveguides 46 and 48. FIG. It is a figure which shows coupling | bonding with the dipole mode of the resonator 50, and the waveguide mode of the waveguides 46 and 48. FIG. It is a figure which shows coupling | bonding with the hexapole mode of the resonator 50, and the waveguide mode of the waveguides 54 and 56. FIG. It is a figure which shows coupling | bonding with the hexapole mode of the resonator 50, and the waveguide mode of the waveguides 54 and 56. FIG. It is a figure which shows coupling | bonding with the hexapole mode of the resonator 50, and the waveguide mode of the waveguides 54 and 56. FIG. It is a figure which shows the structure which combined the structure shown to FIG. 14 (A), and the structure shown to FIG. 18 (A), (B). It is a figure which shows the shape of the waveguide used in FIG.7 and FIG.20. It is a figure which shows a response | compatibility with the propagation mode zone | band of a waveguide used in FIG. 7, and a resonant frequency. It is a block diagram of 2nd Embodiment of the optical switch circuit of this invention. It is a figure which shows a response | compatibility with the propagation mode zone | band of a waveguide used in FIG. 7, and a resonant frequency. It is a figure which shows the output light spectrum from a signal line and a control line, a propagation mode zone | band, and a resonance frequency when resonance mode is directly excited with a broadband light source.

Explanation of symbols

20, 40, 60 Photonic crystal 22, 42, 62 Slab 24, 44, 64 Air hole 26, 28, 46, 48, 54, 56, 66, 68, 74, 76 Waveguide 30, 50, 70 Resonator

Claims (7)

A resonance tunnel filter including a pair of waveguides configured on a two-dimensional photonic crystal and a photonic crystal resonator disposed between the pair of waveguides;
An optical switch circuit that inputs signal light and control light resonating with the resonator from one of the pair of waveguides and takes out from the other, and modulates the signal light with the control light ,
The resonant tunneling filter has first and second resonant wavelengths;
Assigning the first resonance wavelength to the signal light;
An optical switch circuit, wherein the second resonance wavelength is assigned to the control light . A first and second pair of waveguides configured on a two-dimensional photonic crystal, and the first pair of waveguides, and between the second pair of waveguides. Having a resonant tunneling filter composed of a photonic crystal resonator,
Signal light that resonates with the resonator is input from one of the first pair of waveguides and extracted from the other, and control light that resonates with the resonator is input from one of the second pair of waveguides And taking out from the other, and modulating the signal light with the control light ,
The resonant tunneling filter has first and second resonant wavelengths;
Assigning the first resonance wavelength to the signal light;
Assigning the second resonance wavelength to the control light;
The resonator has at least first and second resonance modes,
By matching the symmetry of the field shape of each resonance mode with the symmetry of the field shape of the waveguide mode of the first and second pair of waveguides, the signal light is transmitted to the first pair of waveguides. An optical switch circuit that propagates and propagates the control light to the second pair of waveguides . The optical switch circuit according to claim 2 , wherein
According to the coincidence between the symmetry with respect to the ΓK axis which is the crystal coordination direction of the field shape of the first resonance mode and the symmetry of the field shape with respect to the ΓK axis of the waveguide mode of the first pair of waveguides, Propagating the signal light to the first pair of waveguides by coupling a resonator and the first pair of waveguides,
Due to the mismatch between the symmetry of the field shape of the first resonance mode with respect to the ΓK axis and the symmetry of the field shape of the waveguide mode of the second pair of waveguides with respect to the ΓK axis, An optical switch circuit characterized by not propagating to a pair of waveguides. The optical switch circuit according to claim 3 ,
According to the coincidence between the symmetry of the field shape of the second resonance mode with respect to the ΓM axis orthogonal to the ΓK axis and the symmetry of the field shape of the waveguide mode of the second pair of waveguides with respect to the ΓM axis, And the control light is propagated to the second pair of waveguides by coupling the second pair of waveguides to the second pair of waveguides,
Due to a mismatch between the symmetry of the field shape of the second resonance mode with respect to the ΓM axis and the symmetry of the field shape of the waveguide mode of the first pair of waveguides with respect to the ΓM axis, An optical switch circuit characterized by not propagating to a pair of waveguides. The optical switch circuit according to claim 2 , wherein
By coupling the resonance frequency of the first resonance mode with the band of the waveguide mode of the first pair of waveguides, the resonator and the first pair of waveguides are coupled to transmit the signal light Propagating to a first pair of waveguides;
Light that does not propagate the signal light to the second pair of waveguides due to a mismatch between the resonance frequency of the first resonance mode and the band of the waveguide modes of the second pair of waveguides Switch circuit. The optical switch circuit according to claim 5 , wherein
By combining the resonance frequency of the second resonance mode and the band of the waveguide mode of the second pair of waveguides, the resonator and the second pair of waveguides are coupled to transmit the control light. Propagating to a second pair of waveguides;
Light that does not propagate the control light to the first pair of waveguides due to a mismatch between the resonance frequency of the second resonance mode and the band of the waveguide modes of the first pair of waveguides Switch circuit. The optical switch circuit according to any one of claims 2 to 6 ,
The resonator has a hexapole mode in a photonic band gap.