JP2005037684A - Variable characteristic photonic crystal waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photonic crystal optical waveguide element having a variable characteristic function by external current application, to provide its manufacturing method and to provide a high-function device for optical communication utilizing the element. <P>SOLUTION: In the photonic crystal optical waveguide, a polymer and a heater are introduced in the vicinity of a core in a region into which variable characteristics are to be incorporated and propagation characteristics of the photonic crystal optical waveguide is controlled by heating the polymer to be a part of an upper clad to change the refractive index of the polymer. The device for optical communication such as a high-performance optical switch and a variable wavelength filter can be constituted by using electric current control over the Bragg blocking characteristic, the wavelength dispersion characteristic, etc. of the photonic crystal waveguide. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to application of a photonic crystal mainly to optical communication.

  Photonic crystals are two-dimensional or three-dimensional periodic structures with sub-micron to micron periods, and are expected to be used in a wide range as new optical materials. Innovative technology. The directions to be used are mainly dielectric functions such as polarization selection, wavelength selection, delay equalization by delay and refraction, wavelength selection, and the like that strongly depend on wavelength. They are very interesting properties, but on the one hand they are passive circuit functions with fixed properties. In order to widen the application range, it is desirable to give it some variable characteristic function, but no such means has been known. Therefore, there are no resonators, Bragg reflectors, directional couplers, superprisms, and attenuators, which are important types of photonic crystal waveguide elements, and there are no switches or temperature characteristic compensators. I didn't find anything to list.

Recently, a photonic crystal having a variable mechanism combining a photonic crystal and a liquid crystal has been proposed (Patent Document 1). According to this, by loading the liquid crystal on the cladding portion of the waveguide type photonic crystal, the refractive index of the cladding is adjusted by the electric field, and the propagation constant of the waveguide mode is controlled. As the photonic crystal waveguide, the self-cloning type described in Patent Document 2 is used. Since this method can form a photonic crystal very stably, it is a method suitable for practical use.
However, there are several problems with refractive index control using liquid crystals. One is that the change in refractive index is anisotropic. In the first place, liquid crystals are made of needle-like molecules and control the direction of the molecules, so it is impossible to give the same amount of change in refractive index to the light propagation direction or the polarization direction. is there. The other is that in the liquid crystal, it is important to align the molecular direction, and the alignment process of the base substrate loaded with the liquid crystal becomes complicated.
Japanese Patent Application No. 2002-247783 JP 2001-83321 A JP 2001-91701 A Shojiro Kawakami, Osamu Hanaizumi, Nao Sato, Yasuo Ohtera, Takayuki Kawashima, Noriaki Yasuda, Yoshihiko Takei, Kenta Miura: “Creation and application of 3D photonic crystals by self-cloning” IEICE Transactions CI, Vol. J181-CI, No. 10, pp. 573-581. T.A. Baba, et al. , "Observation of light propagation in photonic crystal optical waveguides with bends," Electron. Lett. , Vol. 35, no. 8, pp. 654-655, April 1999. Takashima Kawashima, Atsushi Fujimura, Nao Sato, Shojiro Kawakami, “Preparation Technology of Photonic Crystals by Self-Cloning”, Journal of Crystal Growth Society of Japan, vol. 28, no. 1, pp. 13-18, 2001) S. Suzuki, “Recent progressive on WDM filters and optical switches using silica-based planar lightwave technologies, Censitive Technology,” Seventh Optoelectronics. 432-433, July 2002. H. Kosaka, et al. "Superprism phenomena in photonic crystals," Physical Review B, vol. 58, no. 16, pp. R10096-R10099, 15 October 1998.

The present invention is to solve the anisotropic refractive index change and the complexity of orientation, which are problems of the photonic crystal control mechanism by the liquid crystal. The object of the present invention is to control the phase change amount, band gap and group velocity by changing the propagation constant of light propagating through the photonic crystal waveguide using the thermo-optic effect of the polymer material, It provides variable functions such as wavelength filter, branching, and group delay.

The present invention is as follows.
(1) The photonic crystal waveguide has a polymer in a part of the clad, and a means for heating the polymer is provided in the vicinity thereof to control the waveguide characteristic or cutoff characteristic of the photonic crystal waveguide. Photonic crystal waveguide (2) A photonic crystal having a heterostructure is used at least in part. (3) The photonic crystal waveguide according to (1) above (3) A photonic crystal produced by a self-cloning method The photonic crystal waveguide according to the above (1), wherein the photonic crystal having a heterostructure produced by the self-cloning method is used at least in part. Photonic crystal waveguide described in (1) above (5) Operates near the X point or Γ point of the photonic crystal The photonic crystal waveguide according to (1), (2), (3) or (4), characterized in that (6) The photonic crystal waveguide according to (1), (2), (3) or (4) A photonic crystal waveguide characterized in that temperature characteristics are compensated or the phase amount of a branch is adjusted by using a waveguide. (7) A resonator including a plurality of Bragg blocking portions is the above (1) or (2) or (3 ) Or (4), which is composed of a photonic crystal waveguide and whose resonance wavelength can be changed by a common polymer control unit. (8) A plurality of Bragg blocking portions that are collectively variable or individually variable. (1) or (2), wherein the position where the Bragg reflection occurs depending on the operating wavelength is variable by one or more polymer control parts. Alternatively, the Bragg reflection waveguide according to (3) or (4) (9) Two adjacent photonic crystal waveguides operating as a directional coupler are the above (1) or (2) or (3) or (4 And a variable degree of coupling by sharing a control polymer. (10) A 3 dB directional coupler composed of a photonic crystal waveguide was used. An optical device comprising the photonic crystal waveguide of (1), (2), (3), or (4) in at least one of the two branches of the Mach-Zehnder circuit (11) An optical device characterized in that the two branches of the Mach-Zehnder circuit in the device are provided with the resonator according to the above (7) or the Bragg reflection waveguide according to the above (8) having the same characteristics. Path (12) The photonic crystal waveguide described in the above (1), (2), (3) or (4) has an oblique periodic structure in the waveguide, and a wave is transmitted at the operating wavelength, or Bragg A variable Bragg reflector (13), one of which is reflected in an oblique direction by blocking and switched by a polymer control unit (13). A plurality of photonic crystals intersect at one or more points. The waveguide has the above feature (1), (2), (3) or (4), and at least one of the intersecting portions is caused by a polymer portion shared by a plurality of waveguides so that the optical path goes straight or by oblique Bragg reflection. An optical switch characterized in that it is transferred to or controlled by the other waveguide (14) It is wavelength dependent by using the photonic crystal waveguide of (1) or (2) or (3) or (4) above. In the photonic crystal waveguide (15) linear waveguide or curved waveguide having a super prism action characterized in that it is possible to control the property or the incident angle dependence, the above (1) or (2) or (3) or (4) A variable optical attenuator characterized by being provided with the structure

  As a method for producing a photonic crystal, a periodic multilayer film production method including sputter etching as a part thereof is effective because it has a self-searching / replicating effect of a steady shape (Patent Document 2). In this patent application, this method is called “self-cloning method”. It is also used in a slightly narrow sense in combination with diffusive deposition, and has been used in a film forming method by a combination of sputter etching and sputter film formation (Non-patent Document 1). Note that processes having a sputter etching effect as a substance are included in the above category, although the name does not clearly indicate sputter etching, such as so-called ECR sputtering.

  Heterostructured photonic crystal (also called lattice-modulated photonic crystal) means that different periodic structures such as lattice type, lattice orientation, or lattice constant are formed on the border or gradually changing Words. Each region can be designed to have different optical properties. The most convenient way to make it is as follows. A heterostructure photonic crystal is obtained by forming a concavo-convex pattern of a plurality of regions having different lattice types or lattice constants adjacent to each other on the substrate plane, and forming a photonic crystal by self-cloning thereon. . It is of course possible to change the lattice constant in the thickness direction.

  Next, control of the waveguide characteristics of the photonic crystal waveguide will be described using a two-dimensional model waveguide region for simplicity. FIG. 2 shows a uniform waveguide in a direction perpendicular to the plane of the paper, where a portion of the upper cladding of the photonic crystal is replaced with a uniform dielectric. The columnar column 201 is a two-dimensional photonic crystal forming a core, and the columnar column 202 having a small diameter is a two-dimensional photonic crystal forming a cladding, and is a heterostructure photonic crystal in the sense that it is formed from different types of photonic crystals. It is a waveguide. The core portion has a relatively high average dielectric constant and the cladding has a lower average dielectric constant. The light guided by the core / cladding structure has an electromagnetic field skirt in the uniform dielectric layer 203. When the dielectric constant of the dielectric increases / decreases, the effective refractive index (propagation constant / wave number in vacuum) of the waveguide mode also increases / decreases.

In the photonic crystal waveguide, the cutoff region due to Bragg reflection is also important, as is the mode waveguide. In fact, many of the functions unique to photonic crystals are realized in the Bragg region. In the heterostructure photonic crystal waveguide, the cutoff region can be controlled by a uniform dielectric layer as well as the waveguide region. Details have been described in Patent Document 1, but here a conclusion will be shown. In other words, even in the Bragg cutoff region, the lateral confinement of the electromagnetic field (in the plane perpendicular to the propagation direction) can be inferred from the electromagnetic field distribution defined outside the black cutoff region, and the band gap of the guided mode is between the core and cladding. The band gap of each region is approximately obtained by weighting the power of the electromagnetic field distribution. Therefore, even when a uniform polymer material (band gap = 0) is used for a part of the clad, the waveguide mode exhibits a Bragg cutoff characteristic without leakage if an appropriate electromagnetic field component exists in the clad.

Further, if the dielectric constant of the uniform dielectric provided cladding (epsilon and _D) increases or decreases the value by the control signal from the outside, the propagation constant β is reduced for example epsilon _D is increased (For example, 1%), the Bragg cutoff frequency region of the waveguide moves to a correspondingly lower frequency band (also 1% in this example).

  As described above, in the photonic crystal waveguide, when a part of the cladding is replaced with another dielectric such as a polymer, various variable characteristics can be realized, and the waveguide characteristics can be controlled. (The waveguide characteristic here is a general term for characteristics of a normal propagation band where β is a real number, a Bragg cutoff area where a complex number is used, or a leakage wave.) To use this effect A heterostructure photonic crystal waveguide having a core and a clad formed of the same photonic crystal is suitable. However, in the so-called slab type photonic crystal waveguide (Non-Patent Document 2), the concept described below can be applied by providing a buffer layer so as to provide an appropriate distance between the central portion of the waveguide and the polymer. .

First, a heterostructure photonic crystal waveguide for adding a variable mechanism will be described. A particularly suitable structure to which the present invention is applied is an optical waveguide using a self-cloning photonic crystal lattice modulation technique. A configuration example and an operation principle will be described.
FIG. 4A shows an example of a specific configuration of a “lattice constant modulation type” optical waveguide composed of a heterostructure of a plurality of two-dimensional photonic crystal regions having different lattice constants. In this structure, for example, a transparent material 402 having a high refractive index and a transparent material 403 having a low refractive index are alternately arranged on a substrate 401 having periodic irregularities formed on the surface by a combination of electron beam lithography and dry etching. It is formed by stacking by the self-cloning process. As the high refractive index material, for example, amorphous Si (a-Si), tantalum pentoxide (Ta ₂ O ₅ ), niobium pentoxide (Nb ₂ O ₅ ), titanium oxide (TiO ₂ ), or the like is used. Further, quartz (SiO ₂ ) or the like is used as the low refractive index material. At this time, as described above, the unevenness on the initial substrate is changed depending on the location, and the thickness of the transparent material 402 and the transparent material 403 is changed in a part from the lowermost layer to the uppermost layer of the multilayer film. Thus, a heterostructure photonic crystal in which regions having different lattice constants (405 to 408 in FIG. 4B) are sterically combined is formed (Patent Document 3). In order to connect the concavo-convex shape on the substrate and the steady wave shape by self-cloning, a shaping layer 404 made of a material having substantially the same refractive index as that of the substrate is laminated between the substrate 401 and the first layer of the multilayer film. Also good. This is common to all self-cloning multilayers appearing in the present invention. For later explanation, FIG. 4B shows a cross section of the heterostructure photonic crystal of FIG. 4A divided into regions having a constant lattice constant.

  FIG. 5 shows another configuration example of the photonic crystal waveguide based on the lattice modulation technique. In this structure, the regions 405 and 407 in FIG. 4B are both composed of flat alternating multilayer films, that is, one-dimensional photonic crystals. In FIG. 5, the effective refractive index for y-polarized light whose Bloch wave vector is directed in the z direction is generally greater in the one-dimensional crystal region than in the two-dimensional crystal region. Therefore, also in this configuration, the magnitude relationship of the refractive index of each region is similar to that in FIG.

  FIG. 6 shows another configuration example of the photonic crystal waveguide based on the lattice modulation technique. This is a two-dimensional self-cloning crystal composed of a concavo-convex multilayer film in which a plurality of regions are combined by shifting the crystal orientation by an angle θ within the yz plane of the figure. As described above, each part of the crystal behaves as an artificial anisotropic medium with respect to incident light. Therefore, if the number of layers of the multilayer film, the degree of film thickness modulation, the bending angle θ of the crystal orientation, etc. are appropriately set In addition, a light confinement structure based on a difference in refractive index can be realized. Here, θ is an angle of about 10 degrees to 30 degrees, for example. In the example of FIG. 6, light is confined in a region 601 in the cross section and propagates along a region 603 sandwiched between clads 602 formed by shifting the crystal orientation. The configuration example of the optical waveguide shown above is only an example of a structure that can be realized by using a photonic crystal by a self-cloning method, and the form of the waveguide is not limited to this.

By the way, a photonic crystal behaves as if it is a transparent medium that is anisotropic with respect to light of that wavelength when the shape and dimensions of its unit structure meet certain conditions with respect to the wavelength of light used. . For example, in the structure of FIG. 4A, the transparent material 402 is tantalum pentoxide (Ta ₂ O ₅ ) having a refractive index n = 2.1, and the transparent material 403 is quartz (SiO ₂ ) having a refractive index n = 1.5. It is assumed that the lattice constants in the stacking direction indicated by L _x1 and L _x2 in the drawing are L _x1 = 0.73 μm and L _x2 = 0.62 μm, respectively, and the lattice constants L _y1 and L _{y2 in} the horizontal direction are L _y1 = It is assumed that 0.62 μm and L _y2 = 1.095 μm. In this case, the principal component of the electric field vector for example, in FIG oriented in the y direction, each part of the crystal with respect to light having a wavelength of 1.55μm with Bloch wave vector k _z in the z-direction serves as a transparent material. FIG. 7A shows an example of the film structure of the region 405 in each of the cross-sectional regions in FIG. The effective refractive index N _eff of light traveling in the z-axis direction in such a structure is the Bloch wave vector k _z and the wave number k _{0 in} the vacuum of the light (= 2π / λ, λ is the wavelength in the vacuum) ), Which can be determined from the photonic band structure. FIG. 8 shows a photonic band structure of a mode having an electric field component mainly in the y direction that propagates in the structure of FIG. 7A in the z direction, calculated by the finite difference time domain method (FDTD method). . In this case, the effective refractive index N _eff = k _z / k ₀ of the crystal region is given by the reciprocal of the slope of the straight line drawn from the origin to the operating point in the lowest order band of FIG. For example, at a wavelength λ = 1.55 μm, the operating point is 801, and the effective refractive index at this point is calculated to be about 1.835. According to the same calculation, the effective refractive indexes of the regions 406, 407, and 408 in FIG. 4B are 1.822, 1.818, and 1.810, respectively. Finally, the crystal has the region 405 as a core. It functions as a channel type optical waveguide. The guided mode light is confined in the region 409 in FIG. 4B and propagates in the z direction. At this time, an example of the dimension of the core region 405 is 5.5 cycles of the multilayer film in the x direction, a thickness of about 4.0 μm, 7 cycles in the y direction, and a width of about 4.3 μm. As in this example, by appropriately setting the spatial arrangement of the lattice modulation, each region of the photonic crystal can function as the core or cladding of the optical waveguide.

When utilizing effects such as photonic band gap and strong wavelength dispersion in waveguides made of photonic crystals, the waveguide must have a periodic structure in the light propagation direction. Is desirable. For example, the waveguide shown in FIG. 6 is an example of such a structure. An example of the relationship between the cross-sectional structure of the film and the photonic band structure in such a periodic waveguide will be described. For example, in a periodic structure having a cross-sectional shape as shown in FIG. 7A, the photonic band structure of light having a Bloch wave vector in the y direction and polarized in the z direction is as shown in FIG. This band structure was calculated by the FDTD method. Here, at a position where the value of the horizontal axis is 0 (this is called a Γ point), a photonic band gap opens in the range of 0.52559 ≦ k ₀ ≦ 0.55562 indicated by reference numeral 901. As described above, the film structure represented by FIG. 7A uses the effect of the photonic band gap at the Γ point and the effect of the large wavelength dispersion of the photonic bands above and below the band gap. be able to.

On the other hand, in the formation of a multilayer film by the self-cloning method, by incorporating the effect of reactive ion etching during the film formation process, one of the media is separated as shown in the photograph of FIG. A film structure can be produced (Non-Patent Document 3). In this example, the divided medium is SiO ₂ and the other medium is amorphous Si. Such a structure was approximated by the structure shown in FIG. 7C, and a photonic band structure for y-polarized light traveling in the z direction was calculated by the FDTD method. The results are shown in FIG. As a feature, at the Brillouin zone end (referred to as point X) where the horizontal axis is 1, a photonic band gap opens in the range of 0.14994 ≦ k ₀ ≦ 0.17504 indicated by reference numeral 1201. As described above, the film structure represented by FIG. 7B uses the effect of the photonic band gap at the point X and the effect of the large wavelength dispersion of the photonic bands above and below the band gap. be able to.

In addition to the above, various waveguide configurations are possible using the self-cloning method. FIG. 10 shows another configuration example of the waveguide. That is, the lower clad layer 1002 is formed on the substrate 1001 on which the concavo-convex pattern is formed by the self-cloning method, and then the core layer 1003 made of a single layer or a multilayer film of several cycles is formed. An upper cladding layer 1004 may be formed thereon. Light propagates through the core layer in the yz plane. Here, in order to efficiently use the effect of the photonic band gap and the effect of wavelength dispersion at the edge of the photonic band, the period Λ of the unevenness is determined by the in-medium wavelength λ (= λ ₀ / n, λ ₀ is a wavelength in a vacuum, and n is an effective refractive index of the core layer medium), and preferably 0.5λ ≦ Λ ≦ λ. The thickness of the core layer is preferably set so that the waveguide is in a single mode in the x direction in the figure. For example, the lower cladding layer is made of Ge-doped SiO ₂ (refractive index 1.52), the core layer is made of Ta ₂ O ₅ (refractive index 2.1), and the upper cladding is made of SiO ₂ (refractive index 1.5). When the wavelength of light is 1.55 μm, the thickness of the core layer is 0.2 μm to 0.3 μm.

  Next, by using a material having a variable refractive index as a part of the cladding of the photonic crystal waveguide shown in FIGS. 4A, 5, 6, and 10, the propagation constant, the electric field distribution of the mode, etc. can be derived. A method of making various characteristics of the waveguide variable will be described. The basic operation principle is the same for the photonic crystal waveguide of FIG. 4A, FIG. 6, FIG. 10, or other structures.

Here, an example will be shown in which the guided light characteristics in a self-cloning photonic crystal waveguide are controlled by the variable effect of the refractive index of a polymer or the like. FIG. 1 is a plan view showing the concept and a cross-sectional view taken along the line AB. As shown in the cross-sectional view, in a photonic crystal waveguide structure composed of a core 101 and a clad 102, a polymer filling groove 103 formed up to the vicinity of the core 101 is filled with a polymer 104. A pair of thin film heaters 105 for heating the polymer are formed in the vicinity of the polymer. In the embodiment, there is a pair, but the shape and the number of heaters are not limited. The thin film heater 105 is made of, for example, Au / Pt / Ti. However, the material is not limited to this. The Au portion on the surface has an effect that wire bonding with Au wire can be used when protecting the heater portion and taking out the wiring to the external circuit. In order to increase the heat confinement efficiency by the thin film heater 105, a heat insulating groove 106 is formed in the periphery so as to sandwich the polymer 104 and the thin film heater 105. When the polymer 104 is heated by the thin film heater 105, the refractive index of the polymer 104 changes, and as a result, the characteristics of the guided light passing through the core 101 can be changed.
In the photonic crystal waveguide, it is necessary to accurately separate the polymer 104 from the core 101 by a certain distance D (0 ≦ D ≦ 10 μm). In addition, the surface roughness of the wall surface and bottom surface of the polymer filling groove 103 is preferably low. However, unlike a variable optical material such as liquid crystal, the alignment is not a problem because it is not a problem.
Specific production examples are shown below.

An example of a manufacturing process is shown in FIGS. In this example, an optical waveguide made of self-cloning photonic crystal is processed by dry etching to add functionality to the photonic crystal waveguide through polymer filling / patterning and thin film heater formation. It is.
Here, a manufacturing method with application to self-cloning photonic crystals in mind will be described. However, photonic crystals manufactured by methods other than the self-cloning method are also used for polymer filling grooves and polymer fillings described below. A forming method can be applied.

First, a method for producing a self-cloning photonic crystal will be described. The substrate is typically Si or SiO ₂ (quartz), but other substrates can be selected according to the use of the photonic crystal. The structure of the surface of the substrate is processed into irregularities by patterning the substrate surface into a line & space shape by electron beam exposure, photolithography using a stepper and dry etching. The dimensions of Line & Space are on the order of submicrons in terms of line width, spacing, and depth. A high refractive index layer and a low refractive index layer are alternately laminated on the substrate by sputtering. Here, for example, a Ta ₂ O ₅ film is used as the high refractive index layer, and an SiO ₂ film is used as the low refractive index layer. The sputtering apparatus to be used preferably has an apparatus configuration in which RF (Radio Frequency) power is applied to the target and the substrate, respectively. Using the apparatus, a method of forming a film while alternately applying RF power to the target and the substrate, or a method of forming a film while simultaneously applying RF power to the target and the substrate is used. The film thickness is determined by the characteristics of the target device. When depositing each film, the film is deposited while maintaining a certain cross-sectional shape by the self-cloning method.

As shown in FIG. 17A, a substrate 1701 having a predetermined concavo-convex shape having a line width, interval and depth on the order of submicron is manufactured. As described above, the surface of the substrate 1701 is patterned into a line & space shape by electron beam exposure or photolithography using a stepper and a dry etching method, and processed into irregularities. The core portion remains flat as shown in FIG. 5, but its width is determined under the condition that the waveguide is in single mode. Here, for example, the thickness is 3 μm.

A photonic crystal film is formed on the substrate 1701 by a self-cloning method using a sputtering apparatus. A configuration diagram of the sputtering apparatus is omitted here. After forming the shaping layer 1702 as shown in FIG. 17 (b), a lower cladding layer 1703 is formed as shown in FIG. 17 (c), and as shown in FIG. An upper clad layer 1707 is continuously formed. The planarizing layer 1708 is a layer that planarizes the surface of the wavy photonic crystal by appropriately selecting the sputtering conditions. The high refractive index material (Ta ₂ O ₅ ) 1704 and the low refractive index material (SiO ₂ ) 1705 forming these are adjusted so that the refractive index, shape, and film thickness ratio are optimized.

As shown in FIG. 18A, a mask 1801 is formed to dry-etch the photonic crystal. The mask 1801 is preferably made of metal in order to improve the side walls of the photonic crystal during etching. However, this is not always necessary, and an organic mask such as a photoresist can also be manufactured.

As shown in FIG. 18B, the photonic crystal film is etched by a dry etching method using the metal mask 1801 described with reference to FIG. By etching, a polymer filling groove 1802 and a heat insulating groove 1803 are formed. For example, if a capacitively coupled RIE apparatus is used to etch with CHF ₃ etching gas, a multilayer structure of SiO ₂ and Ta ₂ O ₅ can be satisfactorily etched. The in-plane distribution can also be suppressed to an extent that there is no problem. Here, it is important to control the distance D from the bottom surface of the polymer filling groove shown in FIG. 1 and the waveguide core to a predetermined value. The distance D must be selected so that the bottom of the field distribution is finite, and is set to 0 to 10 μm. However, since it is preferable that the thickness is as thin as possible, D = 1.0 μm is set in this embodiment. After the dry etching, the metal mask 1801 is removed as shown in FIG.

As shown in FIG. 19A, patterning with a photoresist 1901 is performed to form a thin film heater by a lift-off method. Depending on the material of the thin film heater, this method is not necessarily adopted. Here, the lift-off method is selected because Pt, which is difficult to etch, is used.

Next, as shown in FIG. 19B, a thin metal film 1902 for a thin film heater is formed by performing continuous sputtering in the order of Ti, Pt, and Au by a sputtering method. In view of film quality, it is preferable to use a multi-target sputtering apparatus capable of continuous sputtering without releasing to the atmosphere.

  As shown in FIG. 19C, the thin film heater structure 1903 is formed by removing the photoresist 1901. Even if the material is difficult to etch, the desired shape can be obtained by using this lift-off method.

As shown in FIG. 20A, a polymer 2001 is spin-coated and uniformly applied to the entire surface. Then, it is necessary to dry and solidify sufficiently. Here, the spin coating method is taken as an example, but a method in which a sheet-like polymer material is bonded by thermocompression bonding under vacuum is also conceivable. There is an advantage that the range of material selection is widened by not being bound by the spin coating method.

As shown in FIG. 20B, a metal mask 2002 is patterned on the polymer 2001 formed in FIG. Since O ₂ -RIE is performed to etch the polymer 2001 in a later step, it is preferable to use a metal mask rather than an organic mask. It is also important to select a metal different from the thin film heater 1903.

As shown in FIG. 20C, O ₂ -RIE is performed using a metal mask 2002 to form the shape of the polymer 2001 portion. There is no concern that the thin film heater 1903 will deteriorate due to O ₂ -RIE. Thereafter, as shown in FIG. 21, the metal mask 2002 is removed to complete. It is important that the polymer 2001 is located in the vicinity of the thin film heater 1903 for heating efficiency.

The above is the description of the production example. In the case of actually assembling as a device, the present element is put in a housing and fixed, and wire bonding by Au wire can be used for heater wiring. This is possible because the heater surface is Au. Since wire bonding is possible, connection to an external circuit is easy and the structure is simplified.

  FIG. 11 shows an example of a configuration for making the waveguide characteristics variable by using a polymer thermo-optic effect (hereinafter referred to as TO effect) in a part of the clad of the slab type waveguide structure made of photonic crystal. That is, the lower clad layer 1102, the core layer 1101, and the polymer layer 1104 are disposed on the substrate 401. It is essential that the field distribution of the mode propagating in the core has a finite value even in the polymer layer. An upper cladding layer 1103 having an arbitrary thickness may be provided between the core layer and the polymer layer as long as this condition is satisfied. Here, a configuration example in the case where the upper cladding layer is provided will be described, but the basic operation principle of the waveguide is the same even when the upper cladding layer is not provided. In addition to this, a groove having a predetermined depth may be formed in the upper clad, and a polymer layer may be disposed there.

By applying a current to the thin film heater adjacent to the polymer region and heating it, the refractive index of the polymer changes. Since the electric field of the guided mode has a finite value in the polymer layer, the refractive index of the polymer changes near the equivalent refractive index N _e (= β / k ₀ , β is a propagation constant) of the guided mode. For example, the field distribution of the waveguide mode and the propagation constant change accordingly. Refractive index of the polymer around the N _e, it is necessary to be able to vary the width of about relative refractive index difference of the waveguide (represented by the symbol delta). That is, when the refractive index of the polymer is n, it is only necessary that n can be controlled in the range of (1−Δ) N _e ≦ n ≦ (1 + Δ) N _e . The relative refractive index difference of the waveguide is defined by Δ = (n ₁ ² −n ₀ ² ) / (2n ₁ ² ), where n ₁ and n ₀ are the refractive indexes of the core and the clad, respectively.

  Based on the above configuration, for example, a waveguide with variable radiation amount can be realized. In this case, a cover layer made of a material having a large refractive index is used for the polymer portion. The operation of this type of element will be described using the equivalent cross-sectional structure and refractive index distribution shown in FIG. Here, for simplicity, the lower clad layer, the core layer, and the upper clad layer made of photonic crystals are replaced with layers 1301, 1302, and 1303 having uniform refractive indexes, respectively. In the figure, reference numerals 1304 and 1305 denote a polymer layer and a cover layer having a refractive index of 2.1, respectively. Here, the lower cladding layer and the cover layer are infinitely thick, and the thicknesses of the core layer, the upper cladding layer, and the polymer layer are 2.5 μm, 1 μm, and 9 μm, respectively. The guided light was a TE wave (electric field parallel to the y direction), and the wavelength was 1.55 μm. The traveling direction of light is the z direction.

If there is no polymer layer and cover layer and the upper cladding layer 1303 is semi-infinitely thick, this waveguide becomes a symmetric three-layer slab waveguide, and the equivalent refractive index of the fundamental mode of the TE wave at the wavelength of 1.55 μm is From general optical waveguide theory, N _e = 1.57 is obtained.

  FIG. 14 shows the result of calculating the instantaneous value of the electric field distribution of the formed natural mode in the structure of FIG. 13 by the FDTD method with respect to the refractive indexes of several polymer layers. Here, an example in which the refractive index of the polymer is changed from 1.58 to 1.56 is shown. Strictly speaking, since the refractive index of the cover layer is larger than the refractive index of the core layer, a leaky waveguide is formed in this configuration, but the polymer layer refractive index = 1.58 and 1.56 in FIG. When the refractive index of the layer is relatively low, little power is radiated and propagates confined in the core layer. On the other hand, when the refractive index of the polymer is equal to or greater than the above-mentioned equivalent refractive index (1.57) of the three-layer slab waveguide, most of the electric power is radiated through the polymer layer toward the outside of the cover layer. In FIG. 14, the cases where the polymer refractive index = 1.57, 1.575, and 1.58 correspond to the cases where the radiation is strong, and the significant leakage of the field to the cover layer can be seen. Even when the refractive index of the cover layer is lower than 2.1, the operation is basically based on the same principle.

  In accordance with this principle, if the polymer refractive index is switched between two values of 1.58 and 1.57 with respect to time, this waveguide functions as a waveguide / radiation ON / OFF type optical switch. That is, in the waveguide state, light is output to the exit side of the waveguide, but in the radiation state, power is lost on the way, and the signal does not reach the exit side.

  Further, if the polymer refractive index is continuously finely adjusted, the degree of radiation can be controlled continuously, so that this waveguide functions as a variable optical attenuator.

[Embodiment 1] In this embodiment, a configuration example of a radiation type ON / OFF optical switch composed of a curved waveguide and a variable optical attenuator will be described with reference to FIGS. That is, the curved waveguide 1502 is formed in the self-cloning photonic crystal 1501 using the above-described lattice modulation technique. Here, in the bent portion, the polymer layer 1503 is loaded on the outer peripheral side of the bend. FIG. 15B is a schematic view of a cross section of the element taken along the line AA ′ in FIG. FIG. 16 shows another configuration example of this element. That is, the polymer layer 1603 is configured to have a height similar to that of the core layer 1602 in the film thickness direction. In the above description, the heater for heating is omitted. In the above configuration, first, when the refractive index of the polymer is the same as or lower than the refractive index of the cladding of the waveguide, the photonic crystal cladding 1501 and 1601, the core 1502 and the core 1502 The structure of 1602 is designed. For example, when the effective relative refractive index difference Δ between the core and the clad is about 2.3%, it is desirable that the radius of curvature is about 500 μm or more.
The refractive index is high when the polymer is not heated. If the refractive index of the polymer is set to the equivalent refractive index N _e (= βk ₀ , β is a propagation constant) of the waveguide mode or higher, the power of the guided light is changed to the outer periphery of the bending through the polymer layer. The power of the guided light after passing through the bent portion is reduced (OFF state). Next, when an electric current is applied to the heater to heat the polymer, the refractive index decreases. When the refractive index is made smaller than the equivalent refractive index of the waveguide mode, the guided light passes through the bent portion (ON state).
The magnitude of the refractive index change required for the polymer material to realize such an operation is approximately the relative refractive index difference (Δ) of the original waveguide. That is, when the refractive index of the polymer is n, it is sufficient that n can be controlled in the range of about (1−Δ) N _e ≦ n ≦ (1 + Δ) N _e . By changing the refractive index n of the polymer in a rectangular wave with respect to time with the same or larger width than this width, this element can function as an ON / OFF type optical switch. .

  Further, if the amount of change in refractive index is continuously controlled within the above range, the ratio of the power radiated at the bent portion can be controlled as a continuous amount, so that this element operates as a variable optical attenuator.

[Embodiment 2] This embodiment describes a series of structures for controlling the effect of Bragg reflection in a periodic waveguide using a polymer.

  FIG. 22A shows only the core region 501 extracted from the structure of FIG. A grating 2201 made of a photonic crystal is provided in a direction orthogonal to a part of the propagation direction (z direction). In such a waveguide structure, a photonic band gap (stop band) is formed in a certain wavelength range with respect to light traveling in the z direction. In other words, in this wavelength region, this waveguide functions as a distributed Bragg reflector (hereinafter abbreviated as DBR). In FIG. 22A, the waveguide region 2201B before and after the DBR is a flat multilayer film, but this region may have a two-dimensional periodic structure that is periodic in the y direction or the z direction.

Here, when a polymer is loaded on the upper clad of the waveguide shown in FIG. 22A to obtain the configuration shown in FIG. 22B, and the refractive index of the polymer portion 2207 is changed, the wavelength range of reflection of the DBR is shifted. be able to. In particular, when the wavelength of the incident light and the lambda _1, the refractive index of the polymer 2207 is as light lambda ₁ in the case of n ₁ is in the cutoff range, and when the refractive index of the polymer 2207 is n ₂ Make sure you are out of the stopband and in the passband. If the refractive index of the polymer 2207 is switched between n ₁ and n ₂ under this situation, it is possible to control whether the light of λ ₁ is transmitted or reflected by the DBR. Therefore, it can function as an ON / OFF type optical switch for a specific wavelength.

Further, for incident light in which a wavelength included in the wavelength band of the DBR's stop band and a wavelength that is not the same are mixed, the wavelength in the stop band is reflected, and the wavelength that is not is transmitted. That is, a wavelength selection function can be realized. For example, in the relationship between the stop band and the wavelength as shown in FIG. 23, the wavelengths λ ₁ and λ ₂ are reflected and the wavelengths λ ₃ and λ ₄ are transmitted. Further, by controlling the refractive index of the polymer layer and changing the wavelength band of the stop band 2301, the selectable wavelength range can be controlled.

Further, the DBR having this configuration can function as a variable delay element for light having a wavelength in the passband. A plurality of two or more elements may be arranged in parallel, but are omitted here. In each delay element, the period in the z direction is set so that the propagating light enters a frequency region with a large group delay near the band gap. The band edge wavelength of the propagation mode is changed by changing the refractive index of the loaded polymer layer, and the amount of delay that can be given by each delay element can be controlled in detail. For the wavelength 1.55 μm band, the period in the z direction is, for example, about 0.585 μm. However, this period is not limited and depends on the refractive index and structural parameters of the constituent materials, and also varies depending on the required bandwidth and delay amount. Groove rows parallel to the z-axis direction are formed on the left and right sides of the core and used as in-plane cladding. As a constituent material of the photonic crystal, amorphous Si is used for the high refractive index material. In addition, a dielectric such as Ta ₂ O ₅ or TiO ₂ may be used. For example, SiO ₂ is used as the low refractive index material. The lower clad is laminated for about 10 cycles at a lamination cycle of 0.42 μm. The core layer is laminated for about three periods with a lamination period of 0.468 μm. Further, an upper clad layer having a period of 0.42 μm and one period is provided on the core layer. The thickness of the upper clad is determined in consideration of the confinement strength of the waveguide mode and the variable range of the refractive index of the polymer, but is typically about one cycle to several cycles. With such a design value, the delay time per cycle of the DBR is about 0.1 ps / μm. When the length of the delay element is set to 200 μm, the total delay amount can be 20 ps.

  On the other hand, as shown in FIG. 24A, a configuration in which the DBR period is gradually changed with respect to the traveling direction of the waveguide is also possible. In such a DBR, effective reflection positions 2406, 2407, and 2408 differ for each wavelength of incident light. Accordingly, the time (delay time) until the light incident from the incident port is reflected by the DBR and returned is different depending on the wavelength. It is possible to compensate for the dispersion of the optical fiber transmission line by using the wavelength dependence of the delay time. Here, when the upper clad of the periodic structure is replaced with the polymer 2410 as shown in FIG. 24B, the effective reflection position of each wavelength can be controlled by the TO effect. Functions as a circuit.

  If the refractive index of the polymer is changed in common over the entire surface of the region 2409, the relationship between wavelength and dispersion at a predetermined refractive index becomes a linear relationship, but by continuously changing the heating temperature in the z direction, The relationship between wavelength and dispersion can be controlled more finely. As a method for continuously changing the heating temperature, for example, as shown in FIG. 25, a plurality of heating heaters 2502 are arranged on the polymer portion 2501 to enable control. Also, a similar function can be realized by providing a plurality of the structures shown in FIG.

  Further, as shown in FIG. 26 (a), even in a structure in which a plurality of DBRs shown in FIG. 22 having different periods are provided, which DBR reflects depending on the wavelength, a different delay time is given for each wavelength. be able to. Furthermore, as shown in FIG. 26 (b), the upper clad portion of each DBR is replaced with a polymer, and a temperature is controlled by independently providing a heater in each portion, so that the wavelength band of each DBR's stop band can be made variable. it can. Even within the stop band, the effective reflection position in the DBR at each wavelength can be controlled. Therefore, the delay time can be controlled from the outside for each wavelength.

  When transmission / reflection is controlled by shifting the stop band edge on the long wavelength side, the period of the periodic structure is shortened closer to the incident side, and transmission / reflection is controlled by shifting the stop band edge on the short wavelength side. The period of the periodic structure is lengthened as it is closer to the incident side.

  [Embodiment 3] In this embodiment, a series of methods for spatially separating and extracting signal light of a desired wavelength channel from incident signal light using the DBR described in [Embodiment 2]. State.

  First, as shown in FIG. 27, for each element described in [Embodiment 2], an optical circulator 2703 is placed at the input section, so that light incident from the port 2701 is demultiplexed into the port 2702 and the port 2707 according to the wavelength. An optical demultiplexing circuit can be configured.

  In addition, as shown in FIG. 28, the DBR described in [Embodiment 2] is disposed in the waveguide at an angle in the yz plane with respect to the waveguide direction, so that the light reflected by the DBR is incident. It can be taken out in a direction different from the direction. Even in such a structure, it is possible to realize the light ON / OFF function by shifting the cut-off area described in paragraph 0046. Further, by forming a waveguide at a position where the reflected light in the DBR is emitted, it is possible to control the branching of the light incident from the port 2803 to the port 2805 or the port 2806 by controlling the refractive index of the polymer layer.

  28 is arranged in an array as shown in FIG. 29, an optical switch capable of switching a plurality of input and output paths by the TO effect can be realized. In this case, when the light travels straight in the ON state, and the operation in which the light is reflected in the OFF state, for example, the light incident from the port 2909 is switched to the port 2914 by turning on the DBRs 2903 and 2905. Although the light can be emitted, the light can be emitted to the port 2913 by setting the reference numerals 2903 and 2904 to the OFF state and the reference numeral 2906 to the ON state. By controlling the ON / OFF states of the plurality of switches in this way, light incident from each port can be selectively emitted to any other port. Although eight input / output ports are shown in the figure, it is obvious that a large-scale optical path switching switch can be realized by increasing the number of ports and the switch portion.

  Further, by using the wavelength selection function described in paragraph 0046, not only simple optical path conversion but also light incident from the same input port can be branched into different paths. That is, it is possible to realize a circuit having a complicated function including an optical path conversion function for each wavelength as compared with the conventional optical branching switch in the wavelength division multiplexing communication.

  [Embodiment 4] In this embodiment, an example is shown in which a heterostructure photonic crystal waveguide optical resonator manufactured by a self-cloning method is combined with a polymer, and the resonance wavelength is tuned by temperature control using a heater. FIG. 30A is a schematic diagram of a structure (example) in which a polymer is introduced into an optical resonator having a waveguide function in the z direction. Light is guided in the direction of the arrow in the figure. The waveguide cross section has a structure as shown in FIG. 30B, and FIG. 30A is obtained by cutting AA ′ in FIG. 30B along a plane parallel to the xz plane. The waveguide mechanism is shown in [Best Mode for Carrying Out the Invention]. Here, the core region 3001 with respect to the y direction is formed of a flat multilayer film (one-dimensional photonic crystal), but may be a two-dimensional photonic crystal. The shaping layer described in [Best Mode for Carrying Out the Invention] is inserted between the substrate 3010 and the multilayer film. The resonator part consists of two DBRs 3005 and a cavity 3006 sandwiched between them. By changing the period in the in-plane direction, the two-dimensional photonic crystal can act as a reflector and a transmitter for the same wavelength. The former functions as a DBR and the latter functions as a cavity. Although the cavity is a two-dimensional photonic crystal here, it operates similarly as a flat multilayer film (one-dimensional photonic crystal).

As a material constituting the multilayer film, any material that can be sputtered can be selected due to the nature of the self-cloning method, but it is desirable that the material loss is extremely small (transparent) in a desired wavelength band. Here, a Ta ₂ O ₅ / SiO ₂ system that is transparent to light from the visible light region to the infrared region is taken as an example of the material system. Refractive indexes are about 2.1 and 1.5 respectively at a wavelength of 1.5 μm. In this case, the waveguide structure is, for example, an in-plane period of 1.1 μm of the cladding 3002, the resonator structure is, for example, an in-plane period of 0.8 μm of the DBR 3005, and the in-plane period of 0.6 μm of the cavity 3006. If the 3003 portion is 0.73 μm (3.5 periods) and the clad 3004 portion is 0.60 μm (8.5 periods each), light of a wavelength of 1.5 μm is guided through the core 3007 in the z direction, Light having a specific wavelength in the same wavelength band can be extracted. In the above design, the Bragg cutoff region of the DBR is in the range of wavelength 1.45 to 1.55 μm, and the phase shift in the cavity is an odd multiple of λ / 4, so that the light with the center wavelength of 1.50 μm is transmitted by resonance. To do. These wavelengths can be designed freely according to structural parameters (period, filling rate of each material, etc.). For example, the cutoff wavelength band can be shifted by changing the in-plane period of the DBR. Similarly, if the refractive index of the upper clad is changed by introducing a polymer and controlling the temperature thereof, the cutoff wavelength band of the waveguide mode and the propagation constant of the cavity portion can be changed, so the resonance wavelength is tuned. It becomes possible.

  There are various methods for loading the polymer on the resonator. FIG. 30 (a) shows a case in which holes are formed on the functional region (resonator portion) with FIB to form a polymer introduction region 3008, and then spin coating is performed. This is an example of applying a polymer. When the hole is processed, the upper clad leaves about one cycle (thickness 0.60 μm). In the figure, the heater is omitted. The resonant wavelength can be controlled by changing the refractive index of the polymer layer 3008 by controlling the temperature of the heater. For example, when the temperature is raised by 100 ° C., the resonance wavelength changes by about 20 nm. Thus, the photonic crystal waveguide resonator operates as a wavelength tunable optical resonator by being fused with a polymer.

[Embodiment 5] Here, a variable wavelength ADD / DROP filter can be realized by combining the polymer loaded photonic crystal optical resonator of [Embodiment 4] and a 3 dB directional coupler comprising a photonic crystal waveguide. It shows that. FIG. 31 is a schematic diagram (top view) of the configuration. The waveguide portions are all photonic crystal waveguides, and the cross-sectional structure is the same as that shown in FIG. The core region 3001 of the waveguide may be either a one-dimensional photonic crystal or a two-dimensional photonic crystal. The constituent materials may be any combination that is transparent in the wavelength band to be used. Here, Ta ₂ O ₅ / SiO ₂ system is used as the constituent material.

Here, the 3 dB directional coupler will be briefly described. In the directional coupler, when the coupling length L is ½ of the complete coupling length L _c (L = L _c / 2), the optical power input to one waveguide is 1 in each waveguide. / 2 is divided equally by 2 and output from the opposite port. That is, the power output from the two output ports is attenuated by 3 dB with respect to the input. Therefore, a directional coupler with L = L _c / 2 is called a “3 dB directional coupler”.

  In the structure of FIG. 31, two 3 dB directional couplers are connected in series, and two polymer-loaded resonators 3103 having the same characteristics are arranged in the middle. Here, one resonator may be formed on two waveguides. In this structure, only light of a specific wavelength is demultiplexed from light input to a certain port (wavelength DROP), or conversely, light of a specific wavelength is input to the input light and output ( Wavelength ADD). Furthermore, the wavelength to be demultiplexed or combined can be tuned by changing the refractive index of the polymer by heating the heater. A detailed operation mechanism and a specific example will be described below.

In FIG. 31, it is assumed that various structural parameters of the waveguide portion and the resonator portion constituting the directional coupler are the same as those in [Example 4]. In this case, this structure operates in a wavelength band of 1.5 μm. When light (wavelength component: 1.475 to 1.525 μm) is incident from the port 3104, the optical power is divided into two equal parts by the 3 dB directional coupler 3101, and the divided lights reach the two resonators 3103, respectively. These resonators have a resonance wavelength λ _r = 1.50 μm. The DBR has a Bragg cutoff region with a wavelength of 1.45 to 1.55 μm. At this time, only light having a wavelength of 1.50 μm passes through the resonator 3103. Light having other wavelengths is reflected and returned to the 3 dB directional coupler 3101. The transmitted light having a wavelength of 1.50 μm is recombined by the 3 dB directional coupler 3102 to become one wave, and is output from the DROP port 3107. On the other hand, light other than the wavelength of 1.50 μm returned to the 3 dB directional coupler 3101 is similarly coupled and output from the port 3105.

  The above is the wavelength DROP operation, but the wavelength ADD operation can be performed as follows. That is, when a wavelength 1.50 μm component is input from the ADD port 3106, it is output from the port 3105 according to the same principle as described above. Here, the light having the wavelength component of 1.475 to 1.525 μm input from the port 3104 is output to the port 3105 after the wavelength of 1.50 μm is dropped. In this way, a component with a wavelength of 1.50 μm is added to the output light from the port 3105.

  Here, the two resonators 3103 are of the polymer loading type shown in [Embodiment 4], and the resonance wavelength can be changed. Therefore, the ADD / DROP wavelength can be tuned. Tuning the operating wavelength after manufacturing the ADD / DROP filter is important for improving the manufacturing yield. For example, when the temperature is raised by 100 ° C., the ADD / DROP wavelength changes by about 20 nm.

  The operating wavelength band and the ADD / DROP wavelength can be freely designed according to structural parameters (period, filling rate of each material, etc.). Further, since the resonance wavelength of the resonator 3103 needs to be common even after the heater is heated, the current applied to the heater is common.

  [Embodiment 6] In this embodiment, a variable wavelength ADD / DROP filter using a combination of a polymer loaded resonator and an optical circulator described in [Embodiment 4] will be described.

FIG. 32 is a schematic diagram of the configuration. A heterostructure photonic crystal 3203 is sandwiched between two optical circulators 3201 and 3202. The heterostructure photonic crystal 3203 incorporates a waveguide (core) 3001 and a polymer loaded optical resonator 3103. In this configuration, only light having a specific wavelength can be demultiplexed from input light having a certain wavelength band. Conversely, multiplexing is also possible. The cross-sectional structure of the photonic crystal waveguide is the same as that in FIG. 30B, and the core region 3001 may be either a one-dimensional photonic crystal or a two-dimensional photonic crystal. The constituent material may be transparent in the wavelength band to be used. Here, a Ta ₂ O ₅ / SiO ₂ system is used as the constituent material, and the structural parameters of the waveguide are the same as those in [Example 4]. The operation mechanism will be described below with a specific example.

The light input from the port 3204 travels straight through the circulator 3201 and reaches the resonator portion 3103 through the waveguide 3001. The input light is assumed to have a wavelength band of 1.475 to 1.525 μm. Further, assuming that the structural parameters of the resonator 3103 are the same as those in the specific example shown in [Example 4], the resonance wavelength λ _r (without heater heating) is 1.50 μm. At this time, only light having a wavelength of 1.50 μm passes through the resonator 3103 and is output to the DROP port 3206 via the waveguide 3001 and the circulator 3202. Light having a wavelength other than 1.50 μm is reflected by the resonator 3103 and returns to the circulator 3201, where the optical path is switched and output to the port 3205. In this way, it is possible to DROP a specific wavelength from the input light. On the other hand, when light having a wavelength of 1.50 μm is input from the ADD port 3207, the light enters the resonator 3103 via the circulator 3202 and the waveguide 3001. However, since the resonance wavelength is 1.50 μm, it is transmitted. Thereafter, the optical path is switched by the circulator 3201 and output from the port 3205. That is, the wavelength of 1.50 μm input from the ADD port 3207 is added to the wavelength component of the light output from the port 3205. As described above, the wavelength ADD / DROP operation can be realized in the configuration of FIG.

  Further, the ADD / DROP wavelength is variable depending on the TO effect of the polymer loaded in the resonator 3103. Therefore, this structure operates as a TO effect control type variable wavelength ADD / DROP filter. The operating wavelength band and the ADD / DROP wavelength can be freely designed according to structural parameters (period, filling rate of each material, etc.).

  [Embodiment 7] In this embodiment, the ADD / DROP filters shown in [Embodiment 5] are connected in multiple stages as shown in FIG. 33, and the resonance wavelengths (before heating the heater) are set to different values in each stage. By doing so, it is shown that a TO effect control type multi-channel variable wavelength demultiplexer can be realized.

Consider the case where the variable wavelength ADD / DROP filters described in [Embodiment 5] are connected in five stages as shown in FIG. The constituent materials and the structure of the waveguide are the same as those in [Example 4]. Here, the DROP wavelength, that is, the resonance wavelength λ _r of each of the filters 3301, 3302, 3303, 3304, and 3305 is set to 1.495 μm, 1.500 μm, 1.505 μm, 1.510 μm, and 1.515 μm, respectively. The drop wavelength can be varied by appropriate design of the resonator structure in each filter. These wavelengths are those before heating the heater. For example, when light having a wavelength band of 1.47 to 1.53 μm is input to the port 3306, the wavelength DROP operation is sequentially performed in each filter, and the wavelengths 3495, 3309, 3310, and 3311 are respectively transmitted from the ports 3307, 3308, 3309, 3310, and 3311. Light of 500 μm, 1.505 μm, 1.510 μm, and 1.515 μm is output. The remaining wavelengths are output from port 3312. If more stages are connected, more wavelengths can be dropped.

  Furthermore, since the DROP wavelength of each unit filter is variable depending on the heater heating temperature as shown in [Example 5], the output wavelength from each port can be tuned. Moreover, since individual temperature can be adjusted by arranging individual heaters for each unit filter, the drop wavelength output from each port can be controlled very precisely and freely. Thus, this structure can be used as a tunable multi-channel wavelength demultiplexer.

  Although delay occurs for each output wavelength during demultiplexing, the delay amount can be made equal by appropriately designing the delay equalizer shown in [Example 2] for each wavelength and installing it in each output port. .

  In this embodiment, the operating wavelength band is 1.5 μm, but the wavelength band can be freely set by appropriately designing various structural parameters.

  In the example described in paragraph 0072, the output of each stage is reversed by 180 degrees. However, the output direction can be made uniform by combining the polymer loaded DBR shown in [Example 2]. The method will be described below with reference to FIG.

For example, the resonators 3313 and 3314 of the unit filters 3302 and 3304 in FIG. 33 are replaced with a polymer loaded DBR as described in the second embodiment. The structure of the DBR is selected so that its Bragg cutoff region covers all the used wavelength bands. At this time, the wavelength DROP operation does not occur in the filters 3302 and 3304, and each plays the role of a 180-degree reflecting mirror. Therefore, the output ports are only 3307, 3309, and 3311, and the output directions of the respective wavelengths are aligned to the right in FIG. In this case, the portion on the left side of the DBR of the unit filters 3302 and 3304 is not necessary.

  The DBR used here is not necessarily a polymer loading type, but if a polymer is loaded, a wavelength band reflected by 180 degrees by heating with a heater can be tuned, and high wavelength controllability can be realized.

  [Embodiment 8] A directional coupler can be formed by arranging a plurality of photonic crystal waveguides adjacent to each other. In this embodiment, a configuration example of a directional coupler having a variable amount of coupling, in which a polymer is combined with this, is shown. Here, an example in which a self-cloning photonic crystal is used is shown, but the basic configuration and operation principle are the same even when a photonic crystal having another structure is used.

FIG. 34 shows an example of the structure of the element. That is, the waveguide 3402 and the waveguide 3403 are formed in the self-cloning photonic crystal 3401 by the lattice modulation technique described above. Here, the polymer layer 3405 is disposed on a part of the mode coupling portion 3404 or an upper layer of the entire region, which are close to each other. FIG. 35 is a schematic diagram of an example of a cross-sectional structure taken along line AA ′ of FIG. That is, the lower clad layer 1102 and the core layer 1101 are stacked by a self-cloning method on a substrate 401 having a periodic unevenness partially including a region 3501 having different in-plane lattice constants. The high refractive index medium constituting the multilayer film is, for example, Ta ₂ O ₅ or amorphous Si, and the low refractive index material is, for example, SiO ₂ . In the combination of Ta ₂ O ₅ / SiO ₂ , the lattice constants in the x and y directions are, for example, 0.6 μm and 1.2 μm, respectively. A polymer layer 1104 is disposed thereon with an upper cladding layer 1103 interposed therebetween. Coupling waveguide cores 3502 and 3503 are formed above the region 3501, and the interval 3504 is, for example, a lattice constant in the y direction of one to several periods. FIG. 35 shows a case where two cycles are provided in the y direction. The mode coupling constant of the waveguide 3402 and the waveguide 3403 is a function of the refractive index of the polymer layer when the bottom of the field distribution of the waveguide mode penetrates into the polymer layer. Thus, for example, (N + 1/2) of the complete coupling length L _c the length of the coupling portion 3404 refractive index at 1.57 polymer layer times (N is a nonnegative integer) if designed so that the polymer 34 is adjusted to around 1.57 so that light incident from the port 3406 or the port 3407 in FIG. 34 is output to the port 3408 and the port 3409 with an arbitrary branching ratio centered on 50%: 50%. be able to.

  FIG. 35 shows an example in which a lattice constant modulation type waveguide of the type shown in FIG. 4A having a uniform structure in the light traveling direction is used as the basic configuration of the waveguide. A waveguide having a periodic structure in the light traveling direction as shown in FIG. 10 may be used. As an advantage in the case of using a periodic waveguide, since the complete coupling length can be shortened by using a waveguide mode having a slow group velocity, the physical length of the coupling portion 3404 and the polymer loading portion 3405 can be reduced. Therefore, the entire device can be reduced in size.

Ninth Embodiment FIGS. 36 and 37 show an embodiment of the present invention. 36 (a) and 36 (b) show a core and a clad made of a two-dimensional photonic crystal, and a photonic crystal waveguide comprising the core and the clad is converted into a 1-input 1-output Mach-Zehnder circuit (Mach-Zehnder circuit; It is a schematic diagram of the Example applied to the (MZ circuit). (A) is a top view of the MZ circuit, and (b) is an AA ′ sectional view of the MZ circuit of (a). In FIG. 36 (b), the part surrounded by the dotted line is the core, which is composed of a two-dimensional photonic crystal. The core can also be a one-dimensional photonic crystal. For the substrate, Si or SiO ₂ (quartz) can be used. In this embodiment, a transparent quartz substrate 3601 having a communication wavelength band of 1.3 to 1.7 μm is used.

On the quartz substrate 3601, lines and spaces having a submicron line width, interval, and depth are formed by electron beam drawing and dry etching. On top of that, a multilayer film of a high refractive index film and a low refractive index film is laminated while performing self-cloning by appropriately combining sputter deposition and sputter etching. In this example, Ta ₂ O ₅ was used as the high refractive index material, and SiO ₂ was used as the low refractive index material.

  Within the dielectric multilayer film type photonic crystal, the region where the lattice constant was reduced in the in-plane direction of the substrate was the core, and the region where the lattice constant was increased was the cladding, and the lattice constants were 0.62 μm and 1.095 μm, respectively. On the other hand, in the direction perpendicular to the substrate surface, the region where the lattice constant was increased was the core, and the region where the lattice constant was decreased was the cladding, and the lattice constant was 0.73 μm and 0.62 μm, respectively. With the above configuration, a difference in refractive index between the core region and the cladding region occurs, and the TE polarization can be favorably confined in the core. The details of optical confinement have been described in [Best Mode for Carrying Out the Invention] and will not be described in the present embodiment.

  A Mach-Zehnder circuit is constituted by the two Y branches of the core and the two arm portions 3602-1 and 360, and regions 3604-1 and 3604 and heaters 3605-1 to 360-4 are injected into the upper portion of the arm portion. And loading the polymer. In the present embodiment, the polymer region and the heater are provided in the two arm portions, but a configuration in which the polymer region and the heater are provided in any one of the arms may be employed. Hereinafter, only the case where the polymer region and the heater are installed on the two arm portions will be described.

Next, sputtering film formation using the self-cloning method will be described in detail. FIG. 36B shows a cross-sectional view of the completed photonic crystal core. First, the substrate shaping layer 3608 is formed over the substrate 3601. The substrate shaping layer is inserted in order to make a smooth transition from the irregularities formed by the lines and spaces on the substrate surface to the slope shape of the multilayer film. This substrate shaping layer is not essential. Next, a lower cladding is formed. The Ta ₂ O ₅ film 3609 has a thickness of 310 nm, the SiO ₂ film 3610 has a thickness of 310 nm, and a total of one period (620 nm) is laminated for four periods. A core 3615 is formed on the lower cladding. The Ta ₂ O ₅ film 3611 has a film thickness of 365 nm, the SiO ₂ film 3612 has a film thickness of 365 nm, and a total of one period (730 nm) is laminated for five periods. The thickness of the core layer is 3.65 μm. An upper cladding is formed on the core. 310nm thickness of the Ta ₂ O ₅ film 3613, a 310nm thickness of the SiO ₂ film 3614, for 10 cycles deposited as one period (620 nm) combined.

  Next, the polymer control unit will be described in detail. Both arms are formed with a separation of 1000 μm, and the polymer groove is formed to have a shape of 100 μm square and a depth of 5 μm by, for example, photolithography and dry etching or only by FIB processing. Thereafter, a polymer is applied by spin coating to form a metal thin film (for example, Cr). Pattern regions 3604-1, 2 by photolithography to leave polymer regions. In this embodiment, acrylic type is used as the kind of polymer, but other types of epoxy and vinyl may be used.

  Next, the operation of the photonic crystal waveguide will be described. As shown in FIG. 37A, the propagation light input to the port 3703-1 is ½ of the optical power of the propagation light input from the Y branch to the upper core 3702-1 and the lower core 3702-2. Branch off. When no current is applied to the heaters 3705-1 to 4, the polymers 3704-1 and 3704-1 are at room temperature, and there is no phase change in the upper core 3702-1 and the lower core 3702-2. Therefore, the branched propagation light is combined at the port 3703-2 and output from the port. The loss of output light is approximately equal to the propagation loss of the waveguide.

  On the other hand, as shown in FIG. 37 (b), a case where the polymer 3704-1 is heated and the polymer 3704-2 is not heated will be described. When the polymer 3704-1 is heated, the propagating light in the upper core 3702-1 branched in half by the Y branch feels a change in the refractive index in the polymer portion, and the refractive index felt by the propagating light increases. As a result, the phase of the propagating light is shifted by π. At this time, since the polymer region 3704-2 of the lower core 3702-2 is not heated, it is assumed that the phase of the propagation light of the lower core 3702-2 does not change. As a result, when the propagation lights of the upper core 3702-1 and the lower core 3702-2 are merged at the port 3703-2, the light output can be made zero. In this way, a polymer TO effect control type ON / OFF optical switch can be produced.

  In the above embodiment, only the upper polymer 3704-1 is operated, but the lower polymer 3704-2 can also be driven simultaneously. That is, by raising / lowering the temperature of the polymer disposed on the upper part of the upper core 3702-1 and the upper part of the lower core 3702-2 of the propagating light branched in half by the Y branch, the upper core 3702- 1 and the lower core 3702-2 are controlled in phase difference, and when the phase difference is zero, the optical output at the port 3703-2 is turned on, and when the phase difference is π, the optical output is turned off. Can be. In addition to the above, it is also possible to control the temperature of the polymer so that a phase difference derived from a manufacturing error or the like in the linear portion or the Y branch portion of the photonic crystal waveguide is canceled.

  [Embodiment 10] FIGS. 38 and 39 show an embodiment of the present invention. FIG. 38 is a schematic diagram of an embodiment in which a two-dimensional photonic crystal waveguide is configured and applied to a 2-input 2-output Mach-Zehnder circuit. (A) is a top view of the MZ circuit, and (b) is a BB ′ sectional view of the MZ circuit of (a). In FIG. 38 (b), the part surrounded by the dotted line is the core, which is composed of a two-dimensional photonic crystal. The core can also be a one-dimensional photonic crystal.

  In the present optical circuit, the multilayer film portion and the polymer loading portion have substantially the same configuration as in the case of [Example 9]. The multilayer film part is produced by sputtering film formation using a self-cloning method. Details of the photonic crystal waveguide structure, self-cloning, and heater have been described in [Best Mode for Carrying Out the Invention].

  On the other hand, the present embodiment shown in FIGS. 38 and 39 differs from the [Embodiment 9] in the optical circuit pattern. The optical circuit pattern of this embodiment forms a Mach-Zehnder circuit from the cores 3802-1 and 2 and two core proximity regions, that is, directional coupler units (here, 3 dB couplers) 3803-1 and 3803. In addition to the Mach-Zehnder circuit, the entire device is composed of regions 3805-1 and 3805-1 and a heater region 3806-1 to 4 that inject a polymer into the upper portion of the arm portion. Here, the 3 dB coupler is a directional coupler that equally distributes the optical power of input light to two output ports (about 3 dB). The bond length in the core proximity regions 3803-1 and 2803 is about ½ of the complete bond length. In the present embodiment, the polymer region and the heater are provided in the two arm portions, but a configuration in which the polymer region and the heater are provided in any one of the arms may be employed. Hereinafter, only the case where the polymer region and the heater are installed on the two arm portions will be described.

Next, the operation of the photonic crystal waveguide will be described. As shown in FIG. 39 (a), the case where the polymers 3905-1, 2 are not heated will be described. The input light from the port 3904-1 (optical power is A ₀ ) includes a phase in the waveguide 3902-3 and the waveguide 3902-4 in the 3 dB coupler 3903-1, A ₀ × 1 / √2, It is distributed to A ₀ × j / √2. Here, j is √ (−1). If no current is supplied to the heaters 3906-1 to 3906-4 and the polymer portions 3905-1 and 2 are not driven, there is no phase change of propagating light in the waveguides 3902-3 and 4. Next, in the 3 dB coupler 3903-2, the propagation light A ₀ × 1 / √2 from the waveguide 3902-3 includes A ₀ × 1 / √2 including the phases in the waveguide 3902-5 and the waveguide 3902-6, respectively. × 1 / √2, A ₀ × 1 / √2 × j / √2. On the other hand, the propagation light A ₀ × j / √2 from the waveguide 3902-4 includes the phases in the waveguide 3902-5 and the waveguide 3902-6, respectively, A ₀ × j / √2 × j / √2, A It is distributed to ₀ × j / √2 × 1 / √2. As a result, at port 3904-3, A ₀ × 1 / √2 × 1 / √2 + A ₀ × j / √2 × j / √2 = 0, and the optical output becomes zero. On the other hand, the port _{3904-4 A 0 × 1 / √2 ×} j / √2 + A 0 × 1 / √2 × j / √2 = jA 0 , and the light output is _{A 0.} The loss of output light at the port 3904-3 is a value obtained by adding the propagation loss of the waveguide and the coupling loss of the directional coupler.

On the other hand, as shown in FIG. 39B, the case where the polymer 3905-1 is heated with a heater and the polymer 3905-2 is not heated will be described. By heating the polymer region 3905-1, the propagating light branched in half by the Y-branch senses the change in the refractive index of the propagating light in the upper core 3902-1 at the polymer portion, and the TE polarization of the propagating light The refractive index felt by increases. As a result, the phase of the TE polarization is shifted by π. At this time, it is assumed that the polymer region 3905-1 of the lower core 3902-2 is not heated and the phase of the propagating light does not change. In this state, the optical output at the ports 3904-3 and 4 is obtained in the same manner as described above. In the 3 dB coupler 3903-1, the propagation light distributed to A ₀ × 1 / √2 and A ₀ × j / √2 including the phase in the waveguide 3902-3 and the waveguide 3902-4 is the polymer portion 3905. Only the waveguide in the vicinity of −1 changes in phase by π, and becomes A ₀ × (−1) × 1 / √2 and A ₀ × j / √2, respectively. Next, _{A 0} including propagating light _{A 0 × (-1) × 1} / √2 each phase to the waveguide 3902-5 and the waveguide 3902-6 from the waveguide 3902-3 in 3dB coupler 3903-2 × (−1) × 1 / √2 × 1 / √2, and A ₀ × (−1) × 1 / √2 × j / √2. On the other hand, the propagation light A ₀ × j / √2 from the waveguide 3902-4 includes the phases in the waveguide 3902-5 and the waveguide 3902-6, respectively, A ₀ × j / √2 × j / √2, A It is distributed to ₀ × j / √2 × 1 / √2. As a result, the port _{3904-3 A 0 × (-1) ×} 1 / √2 × 1 / √2 + A 0 × j / √2 × j / √2 = (- 1) × A 0 , and the optical output A ₀ . On the other hand, the port _{3904-4 A 0 × (-1) ×} 1 / √2 × j / √2 + A 0 × j / √2 × 1 / √2 = 0 , and the optical output is zero. The loss of output light at the port 3904-4 is a value obtained by adding the propagation loss of the waveguide and the coupling loss of the directional coupler. In this way, an optical path switching type optical switch can be manufactured.

  In the above embodiment, only the upper polymer 3905-1 is operated, but the lower polymer 3905-2 can be driven simultaneously. That is, the upper core 3902-1 and the lower core are controlled by controlling the refractive indexes of the polymers arranged on the upper part of the upper core 3902-1 and the upper part of the lower core 3902-2 of the propagation light distributed in half by the 3 dB coupler. The phase difference of the propagation light of 3902-2 is controlled, and when the phase difference is zero, the light can be extracted from the port 3904-4, and when the phase difference is π, the optical output can be extracted from the port 3904-3. . In addition to the above, it is also possible to control the polymer so that the phase difference derived from the manufacturing error in the linear part and 3 dB coupler part of the photonic crystal waveguide is canceled. As described above, the optical switch according to the present invention has a feature that the residual signal at the time of OFF is small, that is, a high extinction ratio. It is obvious that a multistage Mach-Zehnder circuit can be used.

  As an optical device to which this structure is applied, a matrix optical switch, a dispersion control element, and the like can be configured by appropriately arranging a photonic crystal core, a dielectric single layer film core, and a directional coupler.

[Embodiment 11] This embodiment relates to control of the super prism effect peculiar to a photonic crystal. FIG. 3 shows a configuration example of a wavelength demultiplexing circuit having a super prism effect in a photonic crystal and a wavelength tuning function using the super prism effect. FIG. 3A is a top view. Light having a wavelength λ ₁ to λ ₃ propagated through the core 302 of the photonic crystal waveguide is incident on a three-dimensional photonic crystal region 301 produced by self-cloning. Here, the center of the unit cell is drawn in a circle. Due to the super prism effect, the propagation direction differs greatly for each wavelength, and wavelength demultiplexing can be performed. The super prism effect is caused by an in-plane periodic structure, and is an effect that the propagation direction changes greatly with a slight wavelength difference near the inflection point of the wave number diagram (Non-patent Document 5).

A manufacturing method is shown below. A square lattice-shaped hole array pattern (with an in-plane period of 0.6 μm) is formed in advance on a portion having a wavelength demultiplexing function on the substrate 303 with a direction of 10 degrees with respect to the z axis as one of the arrangement directions. . Since the waveguide core is flat, it has no pattern, but the surrounding clad 304 forms a groove array pattern (period 0.8 μm) parallel to the z-axis direction. Next, an alternating multilayer film composed of amorphous Si (refractive index 3.2) and SiO ₂ (refractive index 1.5) is laminated by a self-cloning method, and a portion having a wavelength demultiplexing function is a three-dimensional photonic crystal, The waveguide core forms a flat multilayer film, and the cladding forms a two-dimensional photonic crystal simultaneously. Here, the lamination period of the lower clad 305 is 0.7 μm and 10 periods, and the lamination period of the core layer 306 is 0.7 μm and 3 periods. The upper cladding layer 307 is formed by laminating 0.7 μm for one period or two periods. A heater made of a metal film is formed thereon, and the polymer 308 is loaded. However, the structural parameters of the constituent photonic crystals (type of array pattern (triangular lattice as well as square lattice), each film thickness, lamination period, in-plane period, refractive index, uneven height, etc.) Is a value determined by the branching wavelength and the branching angle, and is not limited.

Light enters from the z-axis direction. Since the orientation of the lattice of the photonic crystal is tilted from the light propagation direction, a super prism effect occurs. The effect is that when the wavelength is increased from 1520 nm to 10 nm, for example, the propagation angle changes by about 30 degrees. Although the branching angle strongly depends on the incident wavelength, the band edge wavelength of the propagation mode can be controlled by controlling the refractive index of the upper polymer layer 308. Therefore, control can be performed so that the light propagates in a specific direction with respect to a specific wavelength. The super prism phenomenon has been known so far, but it is difficult to use because it is sensitive to the wavelength. According to this structure, it is possible to control the propagation direction of the super prism effect after fabrication and propagate light of a specific wavelength in a specific direction.
In the method of controlling with liquid crystal, the change in refractive index is anisotropic, but the super prism is not suitable because the propagation direction changes greatly. The refractive index change due to the polymer is isotropic and is particularly suitable for this application.

The figure which shows the method of controlling the optical waveguide characteristic of the photonic crystal waveguide with the refractive index change by heating to the polymer Explanatory drawing with 2D model The figure which shows the Example which controls the super prism effect with the polymer of an upper clad layer (a) Top view, (b) Cross section (A) The figure which shows the structure of the heterostructure photonic crystal waveguide produced by the self-cloning method, (b) The figure which shows the crystal region which comprises a waveguide Diagram showing structure of heterostructure photonic crystal waveguide fabricated by self-cloning method Diagram showing structure of heterostructure photonic crystal waveguide fabricated by self-cloning method FIG. 4A is a diagram showing an example of a cross-sectional structure of a region having a waveguide in FIG. 4A, FIG. 4B is a cross-sectional photograph of an example of a photonic crystal produced by the self-cloning method, and FIG. Schematic representation of the structure of The figure which shows the photonic band structure of a certain direction in the structure of Fig.7 (a) The figure which shows the photonic band structure of a certain direction in the structure of Fig.7 (a), Diagram showing the structure of an optical waveguide fabricated using the self-cloning method Diagram showing the structure of a photonic crystal waveguide loaded with a polymer layer The figure which shows the photonic band structure of a certain direction in the structure of FIG.7 (c) FIG. 11 is a diagram showing a structure modeling the structure of FIG. 11 and its refractive index distribution. The figure which shows the electric field distribution of the light which propagates the structure of FIG. (A) The figure which shows the upper surface of the optical switch or optical attenuator by control of radiated light, (b) The figure which shows the cross section of the optical switch or optical attenuator by control of radiated light (A) The figure which shows the upper surface of the optical switch or optical attenuator by control of radiated light, (b) The figure which shows the cross section of the optical switch or optical attenuator by control of radiated light (A) Diagram showing formation of uneven pattern on substrate, (b) Diagram showing shaping layer deposition, (c) Diagram showing lower clad layer deposition, (d) Core layer and upper clad layer and planarization Diagram showing layer deposition (A) The figure which shows formation of the metal mask for dry etching to a photonic crystal, (b) The figure which shows the groove formation for polymer filling and heat insulation groove | channel formation to the photonic crystal by dry etching, (c) The metal for dry etching Diagram showing mask removal (A) The figure which shows the patterning of the photoresist for lift-off, (b) The figure which shows the film-forming by the sputtering method of the metal for thin film heaters, (c) The formation (lift-off process) of the shape of the thin film heater by the removal of photoresist Figure (A) shows a coating of the polymer by the spin coating method onto a photonic crystal, Figure, of the polymer by _(c) O 2 -RIE showing the formation of _O 2 metal mask for -RIE to (b) a polymer Diagram showing dry etching Complete drawing after removal of metal mask for O ₂ -RIE (A) The figure which shows a part of waveguide with the distributed Bragg reflector (DBR) produced by the self-cloning method, (b) The conceptual diagram of the structure which loaded the polymer on the core layer of DBR. Relationship between stopband, transmitted wavelength, reflected wavelength (A) The conceptual diagram of the structure where the period of the DBR part of FIG. 22 (a) changed gradually, (b) The conceptual diagram of the structure which loaded the polymer on the core layer of DBR. Conceptual diagram of a structure with multiple polymer temperature control heaters (A) Conceptual diagram of a structure in which a plurality of DBR portions having different periods in FIG. 22 (a) are integrated, (b) Conceptual diagram of a structure in which a polymer is loaded on the core layer of the DBR. Conceptual diagram of an optical circuit combining a photonic crystal waveguide and an optical circulator Conceptual diagram of a configuration in which a reflected wave can be extracted in another direction by forming a DBR in a photonic crystal waveguide obliquely with respect to the waveguide direction. Concept of multi-input / output optical cross-connect switch in which the structure of FIG. 28 is arranged in an array (A) Schematic diagram of a structure (example) in which a polymer is introduced into a photonic crystal waveguide optical resonator, (b) Schematic diagram of a cross section of a photonic crystal waveguide Configuration diagram of a variable wavelength ADD / DROP filter using a combination of a polymer loaded optical resonator made of a photonic crystal and a directional coupler Configuration diagram of tunable wavelength ADD / DROP filter by combining polymer loaded photonic crystal optical resonator and optical circulator Conceptual diagram of a tunable multi-channel wavelength demultiplexer that can be realized by combining multiple polymer-loaded optical resonators and directional couplers made of photonic crystals The figure which shows the upper surface of the structure of 8th Example The figure which shows the cross-section of an 8th Example Schematic diagram of an embodiment in which a 1-input 1-output Mach-Zehnder circuit composed of an optical waveguide using a self-cloning photonic crystal and a polymer are fused. Schematic diagram explaining the action when a 1-input 1-output Mach-Zehnder circuit composed of an optical waveguide using a self-cloning photonic crystal and a polymer are fused. Schematic diagram of an embodiment in which a 2-input 2-output Mach-Zehnder circuit composed of an optical waveguide using a self-cloning photonic crystal and a polymer are fused. Schematic diagram explaining the action when a two-input two-output Mach-Zehnder circuit composed of an optical waveguide using a self-cloning photonic crystal is fused with a polymer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Photonic crystal waveguide core part 102 Photonic crystal waveguide clad part 103 Polymer filling groove 104 Polymer 105 Thin film heater 106 Thermal insulation groove 201 Two-dimensional photonic crystal 202 forming a core Two-dimensional photonic forming a clad Crystal 203 Uniform dielectric layer 301 Self-cloning type three-dimensional photonic crystal 302 having a super prism effect 302 Core 303 Substrate 304 In-plane cladding region 305 Lower cladding 306 Core 307 Upper cladding 308 Polymer 401 Substrate 402 High refractive index material 403 Low refractive index material 404 shaping layer 405 lattice constant, one of crystal regions with constant lattice orientation 406 lattice constant, one of crystal regions with constant lattice orientation 407 lattice constant, one of crystal regions with constant lattice orientation 408 lattice constant, lattice One of crystal regions with constant orientation 409 Optical waveguide core 501 Optical waveguide core 601 Optical waveguide core 602 Optical waveguide cladding 603 Optical waveguide core region 801 Point 901 corresponding to a wavelength of 1.55 μm Band gap 1001 Substrate 1002 Lower clad 1003 Core layer 1004 Upper clad 1101 Core layer 1102 Lower clad layer 1103 Upper clad layer 1104 Polymer layer 1105 Cover layer 1201 Photonic band gap 1301 at point X Lower clad layer 1302 Core layer 1303 Upper clad layer 1304 Polymer layer 1305 Cover layer 1501 Photonic crystal portion 1502 Optical waveguide core 1503 Polymer 1601 Photonic crystal portion 1602 Optical waveguide core 1603 Polymer 170 Substrate 1702 Shaping layer 1703 Lower clad layer 1704 High refractive index material 1705 Low refractive index material 1706 Core layer 1707 Upper clad layer 1708 Flattening layer 1801 Metal mask 1802 Polymer filling groove 1803 Thermal insulation groove 1901 Photoresist 1902 Thin film thin film 1903 Thin film heater 2001 Polymer 2002 Metal mask 2201 DBR portion 2201B Input / output waveguide portion 2202 Upper cladding region 2203 Core region 2204 Lower cladding region 2205 Substrate 2206 DBR portion 2207 Polymer 2301 Stopband wavelength region 2302 Passband wavelength region 2401 Period is Gradually changing DBR portion 2402 Upper cladding region 2403 Core region 2404 Lower cladding region 2405 Substrate 2406 Effective reflection of a certain wavelength Position 2407 Effective reflection position 2408 of a certain wavelength Effective reflection position 2409 of a certain wavelength DBR portion 2410 whose period gradually changes Polymer 2501 Polymer 2502 Heater 2601 DBR mirror part 2602 whose period is different Upper cladding area 2603 Core area 2604 Lower side Cladding region 2605 Substrate 2606 DBR mirror part 2607 having a different period Polymer part 2701 Input port 2702 Output port 1
2703 Optical circulator 2704 DBR portion 2705 Photonic crystal 2706 Optical waveguide core 2707 Output port 2
2801 DBR portion 2802 Photonic crystal 2803 Input port 2804 Optical waveguide core 2805 Output port 1
2806 Output port 2
2901 Optical waveguide core 2902 Photonic crystal 2903 DBR portion 2904 DBR portion 2905 DBR portion 2906 DBR portion 2907 I / O port 2908 I / O port 2909 I / O port 2911 I / O port 2911 I / O port 2912 I / O port 2913 I / O port 2914 I / O port 3001 Core area (in-plane direction of substrate)
3002 Clad region (in-plane direction of substrate)
3003 Core region (multilayer stacking direction)
3004 Clad region (Multilayer stacking direction)
3005 DBR region 3006 Cavity region 3007 Core 3008 Polymer introduction region 3010 Substrate 3101 3 dB directional coupler 3102 3 dB directional coupler 3103 Polymer loaded photonic crystal optical resonator 3104 Input port 3105 Output port 3106 ADD port 3107 DROP port 3201 Light Circulator 3202 Optical circulator 3203 Photonic crystal 3204 Input port 3205 Output port 3206 DROP port 3207 ADD port 3301 Variable wavelength ADD / DROP filter 3302 Variable wavelength ADD / DROP filter 3303 Variable wavelength ADD / DROP filter 3304 Variable wavelength ADD / DROP filter 3305 Variable Wavelength ADD / DROP filter 3306 Input port 3307 Output port 3308 output ports 3309 output ports 3310 output ports 3311 output ports 3312 output port 3313 polymer loaded optical resonator (or DBR)
3314 Polymer-loaded optical resonator (or DBR)
3401 Photonic crystal 3402 Optical waveguide core 3403 Optical waveguide core 3404 Directional coupler mode coupling region 3405 Polymer loading region 3406 Port 1
3407 port 2
3408 port 3
3409 port 4
3501 Substrate region 3502 where the core is formed Optical waveguide core 3503 Optical waveguide core 3504 Space between cores of coupled optical waveguide 3601 Quartz substrate 3602-1, Mach-Zehnder arm portion 3603-1, Port 3604-1 , 2 Polymer region 3605-1 to 4 Heater 3608 Substrate shaping layer 3609 Ta ₂ O ₅ film 3610 SiO ₂ film 3611 Ta ₂ O ₅ film 3612 SiO ₂ film 3613 Ta ₂ O ₅ film 3614 SiO ₂ film 3701 Quartz substrate 3702-1 Upper core 3702-2 Lower core 3703-1, 2 Port 3704-1, 2 Polymer region 3705-1-4 Heater 3801 Quartz substrate 3802-1, 2 Core or waveguide 3803-1, 3dB coupler 3804-1 4 port 3805-1, 2 polymer region 380 -1 to 4 heater 3809 substrate shaping layer 3810 _Ta 2 _{O 5} film 3811 SiO ₂ film 3812 _Ta 2 _{O 5} film 3813 SiO ₂ film 3814 _Ta 2 _{O 5} film 3815 SiO ₂ film 3901 quartz substrate 3902-1～6 core or guide Waveguide 3903-1, 3 dB coupler 3904-1-4 port 3905-1-2, polymer region 3906-1-4 heater

Claims (15)

A photonic crystal having a polymer in a part of a clad of a photonic crystal waveguide and having a means for heating the polymer in the vicinity thereof to control a waveguide characteristic or a cutoff characteristic of the photonic crystal waveguide Waveguide 2. The photonic crystal waveguide according to claim 1, wherein a photonic crystal having a heterostructure is used at least in part. 2. The photonic crystal waveguide according to claim 1, wherein the photonic crystal produced by the self-cloning method is used at least in part. 2. The photonic crystal waveguide according to claim 1, wherein a photonic crystal having a heterostructure produced by a self-cloning method is used at least in part. 5. The photonic crystal waveguide according to claim 1, wherein the photonic crystal waveguide operates near an X point or a Γ point of the photonic crystal. A photonic crystal waveguide characterized in that temperature characteristic compensation or branch phase amount adjustment is performed by using the photonic crystal waveguide according to claim 1 or claim 2 or claim 3 or claim 4. A resonator including a plurality of Bragg blocking portions is composed of the photonic crystal waveguide described in claim 1, claim 2, claim 3, or claim 4, and the resonance wavelength can be changed by a common polymer controller. Optical resonator It is possible to have multiple Bragg blocking parts that can be changed collectively or individually, or the period is continuously changing, and the position where Bragg reflection occurs depending on the operating wavelength can be changed by one or more polymer control parts. The Bragg reflection waveguide according to claim 1, claim 2, claim 3, or claim 4. Two adjacent photonic crystal waveguides acting as directional couplers have the features of claim 1, claim 2, claim 3 or claim 4, and variable coupling by sharing a control polymer Directional coupler characterized by having a degree The photonic crystal waveguide according to claim 1, claim 2, claim 3, or claim 4 is provided on at least one of two branches of a Mach-Zehnder circuit using a 3 dB directional coupler composed of a photonic crystal waveguide. Optical device characterized by including 11. An optical circuit comprising a resonator according to claim 7 or a Bragg reflection waveguide according to claim 8, wherein each of the two branches of the Mach-Zehnder circuit in the device of claim 10 has equal characteristics. The photonic crystal waveguide according to claim 1, claim 2, claim 3, or claim 4 has an oblique periodic structure in the waveguide, and transmits a wave at an operating wavelength, or obliquely by Bragg blocking. Variable Bragg reflector characterized in that one of the reflected is switched by the polymer controller A plurality of photonic crystals intersect at one or more points, and each waveguide has the characteristics of claim 1, claim 2, claim 3, or claim 4, and one or more of the intersecting portions are plural. An optical switch characterized in that the optical path travels straight by a polymer portion shared by one waveguide or is shifted to the other waveguide by oblique Bragg reflection A photonic crystal waveguide having a superprism action, wherein wavelength dependency or incident angle dependency can be controlled by using the photonic crystal waveguide according to claim 1, claim 2, claim 3, or claim 4. A variable optical attenuator formed by adding the structure of claim 1 or claim 2 or claim 3 or claim 4 in a straight waveguide or a bent waveguide.

Images