WO2006129501A1

WO2006129501A1 - Waveguide element

Info

Publication number: WO2006129501A1
Application number: PCT/JP2006/310028
Authority: WO
Inventors: Shigeo Kittaka; Keiji Tsunetomo; Tatsuhiro Nakazawa; Kazuaki Oya
Original assignee: Nippon Sheet Glass Company, Limited
Priority date: 2005-05-31
Filing date: 2006-05-19
Publication date: 2006-12-07
Also published as: JP2006337574A

Abstract

A waveguide element (10) comprising a photonic crystal (2) which is a core exhibiting unidirectional periodicity of refractive index and having a bottom face perpendicular to the periodic direction of refractive index and an incoming side inclined surface (2a) and an outgoing side inclined surface (2b) inclining against the bottom face, a light input portion (3), and a light output portion (4). The light input portion (3) lets the light into the photonic crystal (2) through the bottom face. The light entered into the photonic crystal (2) is reflected off the incoming side inclined surface (2a) and propagation light is generated in the photonic crystal (2) by a band on the Brillouin zone boundary. The propagation light is reflected off the outgoing side inclined surface (2b) and the light exits from the bottom face of the photonic crystal (2). The outgoing light from the photonic crystal (2) is led to the light output portion (4). Fabrication is facilitated because of simple structure, and a small waveguide element suitable for vertical coupling can be provided.

Description

Specification

Waveguide element

Technical field

The present invention relates to a waveguide element that uses a one-dimensional photonic crystal as a core.

Background art

[0002] Various optical elements having a structure in which a waveguide is disposed on a substrate, that is, waveguide elements, have already been put into practical use. In particular, recently, a defect waveguide using a two-dimensional photonic crystal (a two-dimensional photonic crystal defect waveguide) has attracted attention, and its research and development has been actively conducted. The structure of this two-dimensional photonic crystal defect waveguide will be described below. First, a two-dimensional photonic crystal having a two-dimensional refractive index periodic structure is formed by forming regular vacancies in a thin film layer using, for example, Si having a high refractive index. This two-dimensional photonic crystal is configured to form a complete photonic band gap in the operating frequency range in a direction having a refractive index periodicity (refractive index periodic direction). A two-dimensional photonic crystal defect waveguide is formed by providing linear defects in the two-dimensional photonic crystal. Light can propagate through the defect part of this two-dimensional photonic crystal defect waveguide, and cannot propagate through the area where no defect is provided. For this reason, the light entering the defective portion is confined in the defective portion and can propagate without leaking. Therefore, this two-dimensional photonic crystal defect waveguide can be bent at a steep angle (steep angle). By using this two-dimensional photonic crystal defect waveguide as a wiring, the degree of freedom in designing an optical circuit is increased, and the optical circuit can be downsized or integrated. Further, by using this two-dimensional photonic crystal defect waveguide as a part of the optical element, the optical element can be miniaturized.

[0003] Furthermore, it is possible to cause a group velocity abnormality in the light propagating in the two-dimensional photonic crystal defect waveguide. Therefore, when this two-dimensional photonic crystal defect waveguide is used as a part of an optical element, the nonlinear effect can be increased to improve the characteristics of the optical element and reduce the size. .

[0004] Waveguide elements using two-dimensional photonic crystals are, for example, Patent Document 1, Patent Document 2, It is disclosed in Patent Literature 3, Patent Literature 4 and Patent Literature 5. In practice, it is common to use a waveguide that is a combination of the two-dimensional photonic crystal defect waveguide and a simple silicon wire waveguide with small propagation loss.

[0005] Further, a waveguide element using a one-dimensional photonic crystal that can be easily manufactured because of its simpler structure than a two-dimensional photonic crystal has been proposed (for example, patent literature). 6).

[0006] Further, it has been proposed to use an optical circuit including such a waveguide element in combination with an electronic circuit. Specifically, an optical circuit may be combined with an electronic circuit including a light emitting unit and a light receiving unit. Then, the optical signal output by the light emitting portion of the electronic circuit may be received by the optical circuit, and the optical signal output by the optical circuit force may be received by the light receiving portion of the electronic circuit. In this way, by combining the optical circuit and the electronic circuit, a circuit having high-speed processing by the optical circuit and flexible processing by the electronic circuit is configured.

[0007] When coupling an optical circuit and an electronic circuit, generally, two types of coupling, that is, end surface coupling and vertical coupling, can be considered. FIG. 17A shows a configuration in which an optical circuit and an electronic circuit are end-coupled, and FIG. 17B shows a configuration in which an optical circuit and an electronic circuit are vertically coupled. As shown in FIG. 17A, the end face coupling means that the end faces of the planar electronic circuit 100 and the planar optical circuit 200 are opposed to each other, and the vertical coupling is as shown in FIG. 17B. A planar electronic circuit 100 and a planar optical circuit 200 are arranged one above the other and their upper and lower surfaces face each other. Here, the electronic circuit 100 includes a light emitting unit that outputs an optical signal, a light receiving unit that receives the optical signal, and a conductive wire 101, and the optical circuit 200 includes an output unit that outputs the optical signal and an input unit that receives the optical signal. And.

In the end face coupling shown in FIG. 17A, the end face 102 of the electronic circuit 100 must be provided with a light emitting part and a light receiving part. Similarly, the end face 201 of the optical circuit 200 must be provided with an output part and an input part. Since the electronic circuit 100 and the optical circuit 200 that input and output the optical signal 300 are planar, the areas of their end faces 102 and 201 are smaller than the areas of the other faces. For this reason, the light emitting part, the light receiving part, the output part, and the input part are arranged in a line, and the number of these light emitting parts is limited.

On the other hand, in the vertical coupling shown in FIG. 17B, the electronic circuit 100 and the optical circuit 200 Each main surface (upper surface, lower surface) 103, 202 is provided with a light emitting portion, a light receiving portion, an output portion, and an input portion, respectively. Since the main surfaces 103 and 202 have a larger area than the end surfaces 102 and 201, the number of light emitting units, light receiving units, output units, and input units can be increased. That is, the degree of freedom in circuit design increases. Therefore, it is desirable to use vertical coupling when the electronic circuit 100 and the optical circuit 200 are coupled.

[0010] In the case of a planar optical circuit, the emitted light usually travels in a direction parallel to the main surface of the optical circuit and is emitted from the end surface. Therefore, when using vertical coupling, the emitted light must be bent at a right angle. For example, the wavelength demultiplexing element disclosed in Patent Document 5 can resonate a specific frequency component and extract an optical signal having the frequency component in the vertical direction. For example, since the optical element disclosed in Patent Document 6 includes a prism and a diffraction grating, the optical path can be bent. Therefore, vertical coupling can be easily realized by using such an optical element.

Patent Document 1: JP 2004-212416 A

Patent Document 2: JP 2004-170478 A

Patent Document 3: Japanese Patent Laid-Open No. 2004-296560

Patent Document 4: Japanese Unexamined Patent Application Publication No. 2004-093787

Patent Document 5: Japanese Patent Application Laid-Open No. 2004-119671

Patent Document 6: International Publication No. 05Z008305 Pamphlet

Disclosure of the invention

Problems to be solved by the invention

[0011] Here, in the case of the silicon fine wire waveguide or the above-described two-dimensional photonic crystal defect waveguide, the core diameter is usually not more than 0, which is very small. Therefore, it is difficult to align the optical axis for coupling with external light such as an optical fiber, resulting in a large coupling loss.

[0012] When these waveguides are arranged on a planar optical circuit, the emitted light is emitted in a direction suitable for end face coupling (see FIG. 17A). In order to emit the emitted light in a direction suitable for vertical coupling (see Fig. 17B), for example, an additional manufacturing process such as obliquely machining the exit end face of the two-dimensional photonic crystal defect waveguide at 45 ° is required. Necessary.

[0013] Further, by resonating a specific frequency component, an optical signal having the frequency component is vertically The wavelength demultiplexing element that is extracted in the direction cannot simultaneously extract an optical signal including a plurality of frequency components.

[0014] Further, a waveguide element using a one-dimensional photonic crystal can be easily coupled to an optical fiber because the core diameter of the one-dimensional photonic crystal waveguide is about several πι. However, the conventional one-dimensional photonic crystal waveguide requires a prism and a diffraction grating in order to be suitable for vertical coupling. And since the size of the waveguide element is about 10 m, it is difficult to actually manufacture the corresponding prism and diffraction grating.

[0015] The present invention has been made to solve the above-described problems in the prior art, and can be easily manufactured because of its simple structure, can be miniaturized, and can be made suitable for vertical coupling. An object is to provide a waveguide element.

Means for solving the problem

In order to achieve the above object, the first configuration of the waveguide element according to the present invention has a refractive index periodicity in one direction and a bottom surface perpendicular to the direction having the refractive index periodicity. And a photonic crystal, which is a core, which is inclined with respect to the bottom surface and an incident side inclined surface and a Z or exit side inclined surface, and corresponds to the incident side inclined surface and the Z or exit side inclined surface. A light input part and a Z or light output part arranged on the bottom side of the photonic crystal

The light input portion causes light to enter the photonic crystal through the bottom surface, and the light incident on the photonic crystal by the light input portion is reflected by the incident side inclined surface, Propagated light due to a band on the Brillouin zone boundary is generated in the photonic crystal, and propagating light due to the band on the Brillouin zone boundary propagating in the photonic crystal is generated at the emission side inclined surface in the light output portion. The light reflected from the bottom surface of the photonic crystal is guided.

[0017] The following three forms of the first configuration of the waveguide element are conceivable.

[0018] The first aspect has a refractive index periodicity in one direction, a bottom surface perpendicular to the direction having the refractive index periodicity, and an incident side inclined with respect to the bottom surface! / A photonic crystal that is a core having an inclined surface and an outgoing-side inclined surface, and a light input unit and an optical output that are disposed on the bottom surface side of the photonic crystal so as to correspond to the incident-side inclined surface and the outgoing-side inclined surface And the light input portion allows light to enter the photonic crystal through the bottom surface. The light incident on the photonic crystal by the light input unit is reflected by the incident-side inclined surface to generate propagating light in a band on the Brillouin zone boundary in the photonic crystal. In this aspect, the propagating light is reflected by the emitting side inclined surface, and the light emitted from the bottom surface of the photonic crystal is guided to the output unit.

[0019] The second aspect has a refractive index periodicity in one direction, a bottom surface perpendicular to the direction having the refractive index periodicity, and an inclined surface inclined with respect to the bottom surface. A photonic crystal that is a core, and a light input portion disposed on a bottom surface side of the photonic crystal so as to correspond to the inclined surface, and the light input portion includes the bottom surface in the photonic crystal. The light incident on the photonic crystal by the light input unit is reflected by the inclined surface to generate a propagating light by a band on the Brillouin zone boundary in the photonic crystal. This is the aspect.

[0020] The third aspect has a refractive index periodicity in one direction, a bottom surface perpendicular to the direction having the refractive index periodicity, and an inclined surface inclined with respect to the bottom surface. A photonic crystal that is a core, and a light output unit disposed on a bottom surface side of the photonic crystal so as to correspond to the inclined surface, and the light output unit propagates through the photonic crystal In this embodiment, the light propagated by the band on the boundary of the prismatic zone is reflected by the inclined surface, and the light emitted from the bottom surface of the photonic crystal is guided.

[0021] According to the first configuration of the waveguide element of the present invention, the traveling direction of incident light and Z or emitted light is different from the traveling direction of propagating light. Therefore, a waveguide element suitable for vertical coupling can be realized. In addition, according to the first configuration of the waveguide element, since the propagating light by the band on the Brillouin zone boundary is used, it can function as a light control element. Further, according to the first configuration of this waveguide element, since a one-dimensional photonic crystal is used, the waveguide element can be easily manufactured because of its simple structure and can be downsized. Can be realized.

[0022] In the first configuration of the waveguide element of the present invention, it is preferable that a reflection layer is formed on the incident side inclined surface and the Z or output side inclined surface. According to this preferred example, it is possible to reduce the light loss and increase the coupling efficiency. In this case, the reflective layer is preferably made of a metal film or a dielectric multilayer film. Reflective layer If it is made of a metal film, preferably, according to an example, a reflective layer can be easily formed with high reflectivity. Further, according to a preferred example in which the reflective layer is made of a dielectric multilayer film, the reflective layer can be easily formed.

The second configuration of the waveguide element according to the present invention has a refractive index periodicity in one direction, a bottom surface perpendicular to the direction having the refractive index periodicity, and faces the bottom surface. A photonic crystal that is a core, and the incident side diffraction grating and the Z or exit side diffraction grating provided on the upper surface, and the incident side diffraction grating and the Z or exit side diffraction grating. A light input portion and a Z or light output portion arranged on the bottom side of the photonic crystal, and the light input portion causes light to enter the photonic crystal through the bottom surface, and the light input portion The light incident on the photonic crystal is reflected by the incident-side diffraction grating to generate propagating light due to a band on the Brillouin zone boundary in the photonic crystal. Inside the photonic crystal Propagating light by band on pre Luan zone boundary to seeding is reflected by the emission side grating, characterized in that is derived light emitted from the bottom surface of the photonic crystal.

[0024] The following three configurations are conceivable as modes of the second configuration of the waveguide element.

[0025] The first aspect is provided with a refractive index periodicity in one direction, a bottom surface perpendicular to the direction having the refractive index periodicity, a top surface facing the bottom surface, and the top surface. A photonic crystal that is a core having an incident-side diffraction grating and an output-side diffraction grating, and an optical input disposed on the bottom surface side of the photonic crystal corresponding to the incident-side diffraction grating and the output-side diffraction grating And a light output unit, wherein the light input unit causes light to enter the photonic crystal through the bottom surface, and the light incident on the photonic crystal by the light input unit is Reflected by the incident side diffraction grating to generate propagating light by a band on the boundary of the Brillouin zone in the photonic crystal, and the propagating light is reflected by the output side diffraction grating at the light output portion, and The bottom of the photonic crystal Is an aspect that the light is guided that will be emitted from.

[0026] The second aspect is provided with a refractive index periodicity in one direction, a bottom surface perpendicular to the direction having the refractive index periodicity, a top surface facing the bottom surface, and the top surface. A photonic crystal as a core having a diffraction grating, and the photonic crystal corresponding to the diffraction grating. A light input portion disposed on a bottom surface side of the crystal, and the light input portion causes light to enter the photonic crystal through the bottom surface, and the light input portion causes the light to enter the photonic crystal. The incident light is reflected by the diffraction grating to generate propagating light by a band on the Brillouin zone boundary in the photonic crystal.

[0027] A third aspect is provided with a refractive index periodicity in one direction, a bottom surface perpendicular to the direction having the refractive index periodicity, a top surface facing the bottom surface, and the top surface. A photonic crystal, which is a core having a diffraction grating, and a light output unit disposed on the bottom surface side of the photonic crystal so as to correspond to the diffraction grating. The light output unit includes the photonic crystal. The propagating light from the band on the Brillouin zone boundary propagating in the crystal is reflected by the diffraction grating, and the light emitted from the bottom surface of the photonic crystal is guided.

[0028] According to the second configuration of the waveguide element of the present invention, the traveling direction of incident light and Z or emitted light is different from the traveling direction of propagating light. Therefore, a waveguide element suitable for vertical coupling can be realized. In addition, according to the second configuration of this waveguide element, since the propagating light by the band on the Brillouin zone boundary is used, it can function as a light control element. Further, according to the second configuration of this waveguide element, since a one-dimensional photonic crystal is used, the waveguide element can be easily manufactured because of its simple configuration, and can be miniaturized. Can be realized.

[0029] In the first or second configuration of the waveguide element of the present invention, the traveling direction of light incident on the photonic crystal and the light emitted from the photonic crystal or Z The traveling direction of the photonic crystal is preferably the same as the direction having the refractive index periodicity of the photonic crystal. According to this preferred example, when this waveguide element is used in an optical circuit, vertical coupling can be easily realized.

The invention's effect

[0030] According to the present invention, it is possible to provide a waveguide element that can be easily manufactured because of its simple configuration, can be miniaturized, and is suitable for vertical coupling.

Brief Description of Drawings

FIG. 1 is a perspective view showing a configuration of a waveguide element in accordance with the first exemplary embodiment of the present invention. The

FIG. 2 is a side view showing the configuration of the waveguide element according to the first embodiment of the present invention.

FIG. 3 is a side view for explaining the path of light on the incident side in the waveguide element according to the first embodiment of the present invention.

FIG. 4 is a band diagram corresponding to FIG.

FIG. 5 is a side view for explaining the path of light on the emission side in the waveguide element according to the first embodiment of the present invention.

FIG. 6 is a band diagram corresponding to FIG.

FIG. 7 is a side view showing a configuration of a waveguide element provided with a reflective layer in the first embodiment of the present invention.

FIG. 8 is a side view showing the configuration of the waveguide element according to the second embodiment of the present invention.

FIG. 9 is a side view showing the configuration of the waveguide element according to the third embodiment of the present invention.

FIG. 10 is a perspective view showing a configuration of a waveguide element in accordance with the fourth exemplary embodiment of the present invention.

FIG. 11 is a perspective view showing a specific example in which an optical circuit using a waveguide element according to an embodiment of the present invention and an electronic circuit are combined.

FIG. 12 is a side view showing the configuration of the waveguide element in the example of the present invention.

FIG. 13 is a graph showing an impulse response when L (length of a one-dimensional photonic crystal) = 24.5 mm in an example of the present invention.

FIG. 14 is a graph showing an impulse response when L = 39.5 mm in an example of the present invention.

FIG. 15 is a graph showing the insertion loss when L = 24.5 mm in the example of the present invention.

FIG. 16 is a graph showing insertion loss when L = 39.5 mm in an example of the present invention. [FIG. 17A] FIG. 17A is a perspective view showing a configuration in which an optical circuit and an electronic circuit are end-face coupled in the prior art.

FIG. 17B is a perspective view showing a configuration in which an optical circuit and an electronic circuit are vertically coupled in the prior art.

Explanation of symbols

1 Board

2, 32 1D photonic crystal

2a Incident side inclined surface

2b Output side inclined surface

3, 19 Optical input section

3a, 4a, 14a, 19a

3b, 4b, 14b, 19b collimator lens

3c, 4c, 14c, 19c objective lens

4, 14 Optical output section

5, 5a Incident light

6, 6a Outgoing light

8 Propagating light

10, 10a, 10b, 30, 50 Waveguide element

21a, 21b Reflective layer

32a Incident side diffraction grating

32b Outgoing diffraction grating

40 Optical circuit

0a Inclined surface

41 Lens End Ray

1a micro lens

42 Electronic circuit

2a VCSEL

2b Photosensitive cell 42c conductor

43 Light

51 clad,

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described more specifically with reference to embodiments.

[0034] [Embodiment 1]

A waveguide element according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing the configuration of the waveguide element in the first embodiment of the present invention, and FIG. 2 is a side view showing the configuration of the waveguide element in the first embodiment of the present invention. 1 and 2, the light (electromagnetic wave) propagation direction is the Z-axis direction, the directions perpendicular to the light propagation direction (Z-axis direction) and perpendicular to each other are the X-axis direction and V as the Y-axis direction (the same applies to other embodiments described later!).

As shown in FIGS. 1 and 2, the waveguide element 10 of the present embodiment includes a substrate 1, a one-dimensional photonic crystal 2 provided on the substrate 1, and a one-dimensional photonic crystal 2. A light input unit 3 for allowing light to enter inside and a light output unit 4 for guiding the light emitted from the one-dimensional photonic crystal 2 are provided. Here, the substrate 1 is made of a translucent material.

[0036] The one-dimensional photonic crystal 2 is composed of a laminated structure in which two types of substances having different refractive indexes are periodically and alternately laminated in the Y-axis direction (the thickness direction of the substrate 1). The thickness of each material constituting the one-dimensional photonic crystal 2 is constant, and therefore the one-dimensional photonic crystal 2 has a refractive index periodicity only in one direction (Y-axis direction). Also, the incident side end face 2a and the emission side end face 2b, which are both end faces of the one-dimensional photonic crystal 2, are relative to the XZ plane perpendicular to the Y-axis direction, which is the direction having the refractive index periodicity (refractive index periodic direction) It is inclined by a predetermined angle (inclination angle) (hereinafter, the incident side end surface 2a and the output side end surface 2b that are inclined in this way are referred to as "incident side inclined surface 2a" and "output side inclined surface 2b", respectively. ). The inclination angle of the incident side inclined surface 2a is Φ, and the inclination angle of the output side inclined surface 2b is φ. In addition, incident side inclined surface

a b

The directions of inclination of 2a and the outgoing side inclined surface 2b are opposite to each other. Inclination angle φ

a and tilt angle Φ

Although b may be different from each other, it is preferable to use the same value because it is easier to design and manufacture. The bottom and top surfaces of the one-dimensional photonic crystal 2 are It is perpendicular to the refractive index periodic direction (Y-axis direction) (parallel to the XZ plane).

The optical input unit 3 includes an optical fiber 3 a, a collimator lens 3 b, and an objective lens 3 c, and is disposed on the bottom surface side of the substrate 1. The light input unit 3 causes incident light 5 to enter the bottom surface of the one-dimensional photonic crystal 2 through the substrate 1. In this case, the light input unit 3 is arranged so that the incident light 5 travels toward the incident side inclined surface 2a.

The light output section 4 also includes an optical fiber 4a, a collimator lens 4b, and an objective lens 4c, and is disposed on the bottom side of the substrate 1. The light reflected by the outgoing side inclined surface 2 b is emitted from the bottom surface of the one-dimensional photonic crystal 2 as outgoing light 6. In this case, the light output unit 4 is arranged so that the emitted light 6 is guided to the light output unit 4 through the substrate 1.

Note that the light input unit 3 and the light output unit 4 are not limited to such a configuration.

[0040] Further, it is desirable that the incident angle and the outgoing angle of the incident light 5 and the outgoing light 6 with respect to the substrate 1 are 0 °. That is, it is desirable that the incident light 5 and the outgoing light 6 have the same traveling direction as the refractive index periodic direction of the one-dimensional photonic crystal 2. Thereby, when the waveguide element 10 is used in an optical circuit, vertical coupling can be easily realized.

[0041] In the configuration as described above, the one-dimensional photonic crystal 2 is the core of the waveguide, and air and force surrounding the substrate 1, the upper surface and the side surface of the one-dimensional photonic crystal 2, and the waveguide waveguide. It is. Note that a predetermined material can be disposed around the one-dimensional photonic crystal 2 to form a clad.

Next, the operation of the waveguide element 10 according to the present embodiment will be described.

First, the incident light 5 that has propagated through the optical fiber 3 a is converted into parallel light by the collimator lens 3 b, condensed by the objective lens 3 c, and incident on the substrate 1. Light from the light input unit 3 (incident light 5) propagates through the substrate 1 and then enters the one-dimensional photonic crystal 2 from the bottom surface of the one-dimensional photonic crystal 2. Incident light 5 propagated in the one-dimensional photonic crystal 2 reaches the incident-side inclined surface 2a, is reflected in the Z-axis direction, and propagates in the one-dimensional photonic crystal 2 in the Z-axis direction. The conditions for reflection in the Z-axis direction can be determined from the photonic band structure described later.

[0044] The propagating light 8 propagating through the one-dimensional photonic crystal 2 in the Z-axis direction reaches the exit-side inclined surface 2b. The propagating light 8 is reflected by the inclined surface 2b on the exit side, and the bottom of the one-dimensional photonic crystal 2 Change the course in the direction of the force on the surface (Y-axis direction). Note that the structural force of the photonic band, which will be described later, can be obtained as a condition for reflecting in the axial direction.

Furthermore, the light that is reflected by the exit-side inclined surface 2 b of the one-dimensional photonic crystal 2 and becomes the emitted light 6 is emitted from the bottom surface of the one-dimensional photonic crystal 2. The emitted light 6 from the one-dimensional photonic crystal 2 is incident on the substrate 1, propagates through the substrate 1, and is emitted from the substrate 1 to the outside. The emitted light 6 emitted from the substrate 1 is guided to the light output unit 4. Specifically, the outgoing light 6 emitted from the substrate 1 sequentially passes through the objective lens 4c and the collimating lens 4b and enters the optical fiber 4a.

[0046] The propagating light 8 propagating in the one-dimensional photonic crystal 2 is desirably propagated by a mode on the Brillouin zone boundary in the photonic band structure, thereby functioning the waveguide element 10 as a light control element. Can be made.

[0047] The propagating light 8 propagating in the mode on the Brillouin zone boundary is confined in the XZ plane direction regardless of the propagation direction by satisfying the following equation.

[0048] a / λ <l / (2n)

0 S

Where λ is the wave of propagating light 8 propagating in the one-dimensional photonic crystal 2 in vacuum

0

It is long. A is the refractive index period of the one-dimensional photonic crystal 2. N is one dimension

S

The refractive index of the medium that is in contact with the side surface of the photonic crystal 2, that is, the periodic structure of the one-dimensional photonic crystal 2 and is in contact with the V surface. In this embodiment, as described above, the refraction of air Rate. The confinement condition of the propagating light 8 propagating in the mode on the Brillouin zone boundary in the one-dimensional photonic crystal 2 is disclosed in detail in, for example, International Publication No. 05Z008305 pamphlet.

[0049] The propagation light 8 in the one-dimensional photonic crystal 2 can be known by calculating a photonic band and illustrating it. For example, the photonic band calculation method is described in “Photonic Crystals, Princeton University Press, (1995)” or “Physical Review B, 1991, 44, No. 16, p.8565”. It is described in detail. Therefore, the inclination angle φ of the incident side inclined surface 2a and the inclination angle φ of the outgoing side inclined surface 2b are determined by the above band a b

It can be selected based on the result of the calculation.

[0050] FIG. 3 illustrates the path of light on the incident side in the waveguide element of the present embodiment. The side view of is shown. FIG. 3 is an enlarged side view showing a configuration in the vicinity of the incident-side inclined surface 2a of the one-dimensional photonic crystal 2. In FIG. 3, the light input portion is omitted. As shown in FIG. 3, when light (incident light 5) from a light input section (not shown) passes through the substrate 1 and enters the one-dimensional photonic crystal 2, it is one-dimensional photonic. Two types of refracted light 7a and 7b leak outside the crystal 2. The light other than the refracted lights 7a and 7b is reflected by the incident side inclined surface 2a and becomes propagating light 8 that travels in the Z-axis direction.

FIG. 4 shows a band diagram corresponding to FIG. Figure 4 shows the photo of each of the one-dimensional photonic crystal 2 that is the core, the substrate 1 that is the medium on the incident side of the incident light 5, and the medium that is in contact with the incident side inclined surface 2a (air in this embodiment). The nick band structure is illustrated in the inverse space of the YZ plane. Hereinafter, the band diagram of FIG. 4 will be described with reference to FIG.

[0052] Since the band of the one-dimensional photonic crystal 2 shows periodicity, as shown in FIG. 4, the band of the one-dimensional photonic crystal 2 is shown by a periodic zone method, and at this frequency. There are a first band and a second band. The broken line 11 represents the boundary between the substrate 1 and the one-dimensional photonic crystal 2, and the broken line 12 represents the boundary between the air and the one-dimensional photonic crystal 2 (corresponding to the incident side inclined surface 2a).

The substrate 1 and air are homogeneous media having a uniform refractive index, and as shown in FIG. 4, the bands indicating them are simple circles. The center point of the band of the substrate 1 is a normal line of the broken line 11 representing the boundary between the substrate 1 and the one-dimensional photonic crystal 2, and is located on the line passing through the center point of the one-dimensional photonic crystal 2. The center point of the air band is the normal line of the broken line 12 representing the boundary between air and the one-dimensional photonic crystal 2, and is located on the line passing through the center point of the one-dimensional photonic crystal 2. In addition, the arrows shown in FIG. 4 indicate the energy traveling direction at each of the coupling points A to G on the band, and the energy traveling direction is the normal direction of the band.

In FIG. 4, the incident light 5 on which the substrate 1 side force has also entered is coupled with light from the coupling point A on the second band of the one-dimensional photonic crystal 2. Next, light at the intersection of the line 13 perpendicular to the broken line 12 representing the boundary between the air and the one-dimensional photonic crystal 2 and intersecting the coupling point A and each band propagates in the Y-axis direction at the coupling point A. Combine with light. Here, the incident light 5 incident on the one-dimensional photonic crystal 2 and the propagation mode on the Brillouin zone boundary correspond to the incident-side inclined surface 2a. It is chosen to lie on the same normal of the corresponding dashed line 12. That is, the coupling point A indicating the mode of the incident light 5 and the coupling point B indicating the mode of the propagating light 8 exist on the line 13 orthogonal to the broken line 12.

[0055] Although there are a plurality of coupling points A, these are all equivalent points based on periodicity. The same applies to the connection points B to G other than the connection point A, and the connection points indicated by the same reference numerals represent equivalent points.

[0056] The light from the coupling point A that is incident on the one-dimensional photonic crystal 2 from the substrate 1 side is reflected by the incident-side inclined surface 2a, and the coupling point B on the Brillouin zone boundary of the first band. Combine with the light. However, the light incident on the one-dimensional photonic crystal 2 from the substrate 1 side and the light from the coupling point A may be combined with the light at the coupling point C when reflected by the incident side inclined surface 2a. . In addition, the light from the coupling point A, which is the light incident on the one-dimensional photonic crystal 2 from the substrate 1 side, is combined with the light at the coupling point D and the coupling point E when reflected by the incident side inclined surface 2a. Although there is a possibility, since they proceed again to the incident side inclined surface 2a as a force component from the arrow, they can be ignored. Therefore, the light reflected by the incident side inclined surface 2a is only the light at the coupling point B and the coupling point C.

[0057] In addition, a line 13 that passes through the coupling point A and is perpendicular to the broken line 12 intersects the air band at the coupling point F and the coupling point G. Therefore, the directions indicated by the arrows of the coupling point F and the coupling point G respectively. Refracted lights 7a and 7b are generated on the air side.

That is, the light shown in FIG. 4 is as shown below. The light at the coupling point A is propagating light in the same direction as the incident light 5 incident on the substrate 1 side force one-dimensional photonic crystal 2. The light at the coupling point B and the coupling point C is propagating light in the one-dimensional photonic crystal 2 generated by reflection on the incident side inclined surface 2a. The light at the coupling point F and the coupling point G is refracted light 7a and 7b that leaks to the outside from the incident side inclined surface 2a. Although not shown in FIG. 3, the light at the coupling point C may be reflected back from the one-dimensional photonic crystal 2 toward the substrate 1 side.

Next, the light path in the vicinity of the exit-side inclined surface 2b will be described.

FIG. 5 is a side view for explaining the path of light on the emission side in the waveguide element of the present embodiment. Figure 5 shows the configuration of the exit side inclined surface 2b of the one-dimensional photonic crystal 2. FIG. 5 is an enlarged side view, and the light output unit is omitted in FIG. As shown in Fig. 5, the propagation light 8 in the one-dimensional photonic crystal 2 is reflected by the outgoing inclined surface 2b, and the path is changed to the bottom surface side (substrate 1 side) of the one-dimensional photonic crystal 2. The Outgoing light 6 emitted from the bottom surface of the one-dimensional photonic crystal 2 passes through the substrate 1 and is guided to a light output unit (not shown). Note that two kinds of bending lights 9a and 9b leak to the outside of the one-dimensional photonic crystal 2 on the exit side inclined surface 2b.

FIG. 6 shows a band diagram corresponding to FIG. Fig. 6 shows the photo of the one-dimensional photonic crystal 2 that is the core, the substrate 1 that is the medium on the output side of the output light 6, and the medium (air in this embodiment) that is in contact with the output-side inclined surface 2b. The nick band structure is illustrated in the inverse space of the YZ plane. Hereinafter, the band diagram of FIG. 6 will be described with reference to FIG.

[0062] Since the band of the one-dimensional photonic crystal 2 shows periodicity, as shown in Fig. 6, the band of the one-dimensional photonic crystal 2 is shown by a periodic zone method, and at this frequency. The first band and the second band exist. The broken line 16 represents the boundary between the substrate 1 and the one-dimensional photonic crystal 2, and the broken line 17 represents the boundary between air and the one-dimensional photonic crystal 2 (corresponding to the outgoing side inclined surface 2b).

[0063] The substrate 1 and air are homogeneous media having a uniform refractive index, and as shown in Fig. 6, the bands indicating them are simple circles. The center point of the band of the substrate 1 is a normal line of the broken line 16 representing the boundary between the substrate 1 and the one-dimensional photonic crystal 2, and is located on the line passing through the center point of the one-dimensional photonic crystal 2. The center point of the air band is the normal line of the broken line 17 representing the boundary between air and the one-dimensional photonic crystal 2, and is located on the line passing through the center point of the one-dimensional photonic crystal 2. Also, the arrows shown in FIG. 6 indicate the energy traveling directions at each of the coupling points H to M on the band, and the energy traveling direction is the normal direction of the band. For example, there are a plurality of coupling points H, but these are all equivalent points based on periodicity. The same applies to the connection points I to M other than the connection point H, and the connection points indicated by the same reference numerals represent equivalent points. In FIG. 6, the light that is orthogonal to the broken line 17 representing the boundary between the air and the one-dimensional photonic crystal 2 and intersects the coupling point H and the light at the intersection of each band is the light that couples with the propagating light 8. It is.

[0064] The light at the coupling point H, which is the propagating light 8 on the Brillouin zone boundary, passes through the outgoing inclined surface 2b. The light is reflected and combined with the light at the coupling point I, and becomes the outgoing light 6 that is directly emitted to the outside perpendicularly to the bottom force of the one-dimensional photonic crystal 2. However, there is a possibility that the propagating light 8 is coupled with the light at the coupling point J when reflected by the outgoing side inclined surface 2b. In addition, if the propagating light 8 is reflected by the exit-side inclined surface 2b, there is a possibility that the propagating light 8 may be combined with the light at the coupling point K. So it can be ignored. Therefore, the light reflected by the emission side inclined surface 2b is only the light at the coupling point I and the coupling point J.

[0065] Since the line 18 passing through the coupling point H and perpendicular to the broken line 17 intersects the air band at the coupling point L and the coupling point M, the directions indicated by the arrows of the coupling point L and the coupling point M respectively. Refraction light 9a, 9b is generated on the air side.

That is, the light shown in FIG. 6 is as shown below. Light at the coupling point H is propagating light 8 in the one-dimensional photonic crystal 2. The light at the coupling point I is outgoing light 6 that is reflected by the outgoing side inclined surface 2b and travels toward the substrate 1 side. The light at the coupling point L and the coupling point M is refracted light 9a and 9b that leaks to the outside from the exit-side inclined surface 2b. Although not shown in FIG. 5, the light at the coupling point J may be emitted from the one-dimensional photonic crystal 2 toward the substrate 1 side. The light at the junction point J travels differently from the light at the junction point I.

[0067] Of the light shown in FIGS. 4 and 6, the waveguide element 10 of the present embodiment uses light at the coupling point A (incident light 5) and light at the coupling point B (propagation). Light 8), light at coupling point H (propagating light 8) and light at coupling point I (emitted light 6).

[0068] It is desirable that the light at the coupling point C in FIG. 4 and the light at the coupling point J in FIG. 6 be small. Therefore, for example, in the frequency region where the diameter of the ellipse indicating the second band of the one-dimensional photonic crystal 2 becomes small, the inclination angle φ a and the inclination angle φ are

b Design should be done. As a result, it is possible to prevent the light at the coupling point J from existing. As a result, it is possible to couple the reflected light on the exit side inclined surface 2 b only with the light at the coupling point I.

[0069] In the waveguide element 10 of the present embodiment, a reflective layer may be formed on the incident side inclined surface 2a and the emission side inclined surface 2b. FIG. 7 shows the configuration of a waveguide element provided with a reflective layer in this embodiment. In FIG. 7, members having the same functions as those shown in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof is omitted.

FIG. 7 differs from FIG. 1 and FIG. 2 in that the incident side inclined surface 2a and the emission side inclined surface 2b are different from each other. The point is that the reflective layer 21a and the reflective layer 21b are formed. By forming the reflective layer 21a and the reflective layer 21b in this way, light at the coupling point F, the coupling point G, the coupling point L, and the coupling point M (refracted light 7a, 7b, 9a, 9b) (Figs. However, it does not leak to the outside of the one-dimensional photonic crystal 2 and its energy becomes the energy of propagating light 8 and outgoing light 6. As a result, the light loss can be reduced and the coupling efficiency can be increased.

[0071] As the reflective layer 21a and the reflective layer 21b, for example, a metal film may be used. A material such as silver, aluminum, or gold is particularly desirable as a material for the reflective layer 21a and the reflective layer 21b because it has high reflectivity and can be easily formed. The metal film can be easily formed by, for example, a vacuum deposition method or a sputtering method. In addition to the metal film, a dielectric multilayer film may be used as the reflective layer 21a and the reflective layer 21b. As a material for the dielectric multilayer film, silica, silicon, titanium oxide, tantalum oxide, niobium oxide, magnesium fluoride, silicon nitride, etc., which are generally used as thin film materials and are excellent in terms of durability and film formation cost, etc. Such a material may be used. These materials can be easily formed into thin films by sputtering, vacuum deposition, ion-assisted deposition, plasma CVD, or the like.

In the waveguide element 10 of the present embodiment described above, the traveling directions of the incident light 5 and the outgoing light 6 are substantially perpendicular to the traveling direction of the propagating light 8. Therefore, by using the waveguide element 10 of the present embodiment, an optical circuit suitable for vertical coupling can be realized. In addition, light having a plurality of frequencies can be incident, propagated, and emitted. In addition, the waveguide element 10 of the present embodiment can function as a light control element because it uses propagating light that propagates in a mode on the Brillouin zone boundary in the photonic band structure. Furthermore, since the waveguide element 10 of the present embodiment uses the one-dimensional photonic crystal 2, the waveguide element 10 can be easily manufactured because of its simple configuration, and a waveguide element that can be miniaturized can be obtained. Can be realized.

[0073] [Embodiment 2]

A waveguide element according to the second embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a side view showing the configuration of the waveguide element according to the second embodiment of the present invention. In FIG. 8, members having the same functions as those shown in FIG. 2 are given the same reference numerals, and descriptions thereof are omitted. As shown in FIG. 8, in the waveguide element 10a of the present embodiment, light from the light input unit 3 (incident light 5) is the same as in the case of the waveguide element 10 of the first embodiment. However, the bottom force also enters the one-dimensional photonic crystal 2 through the substrate 1. Then, the incident light 5 is reflected by the incident side inclined surface 2 a to become the propagation light 8 and propagates in the one-dimensional photonic crystal 2. However, unlike the case of the waveguide element 10 of the first embodiment, the propagating light 8 is emitted through the emission side inclined surface 2b without being reflected by the emission side inclined surface 2b. That is, in the waveguide element 10a shown in FIG. 8, the incident light 5 enters the one-dimensional photonic crystal 2 through the substrate 1, but the emitted light 6a is directly emitted from the emission-side inclined surface 2b.

In the waveguide element 10a, as described above, the propagation light 8 is emitted as the emission light 6a from the emission side inclined surface 2b. For this reason, the light output part 14 to which the outgoing light 6a is guided is arranged facing the outgoing side inclined surface 2b. The light output unit 14 includes an optical fiber 14a, a collimator lens 14b, and an objective lens 14c.

[0076] Next, the operation of the waveguide element 10a of the present embodiment will be described.

First, the incident light 5 that has propagated through the optical fiber 3 a is converted into parallel light by the collimator lens 3 b, condensed by the objective lens 3 c, and incident on the substrate 1. Light from the light input unit 3 (incident light 5) propagates through the substrate 1 and then enters the one-dimensional photonic crystal 2 from the bottom surface of the one-dimensional photonic crystal 2. Incident light 5 propagated in the one-dimensional photonic crystal 2 reaches the incident-side inclined surface 2a, is reflected in the Z-axis direction, and propagates in the one-dimensional photonic crystal 2 in the Z-axis direction. The propagating light 8 propagating in the one-dimensional photonic crystal 2 is preferably propagated by a mode on the Brillouin zone boundary in the photonic band structure. The incident side inclined surface 2a may be provided with a reflective layer made of, for example, a metal film or a dielectric multilayer film.

[0078] The propagating light 8 propagating through the one-dimensional photonic crystal 2 in the Z-axis direction reaches the exit-side inclined surface 2b. The propagating light 8 is emitted as outgoing light 6a from the outgoing side inclined surface 2b. The outgoing light 6 a emitted from the outgoing side inclined surface 2 b of the one-dimensional photonic crystal 2 is guided to the light output unit 14. Specifically, the outgoing light 6a emitted from the outgoing side inclined surface 2b of the one-dimensional photonic crystal 2 sequentially passes through the objective lens 14c and the collimating lens 14b and enters the optical fiber 14a. [0079] The waveguide element 10a of the present embodiment can achieve the same effects as the waveguide element 10 of the first embodiment.

[0080] The one-dimensional photonic crystal 2 may not include the exit-side inclined surface 2b. Even if the end face on the exit side of the one-dimensional photonic crystal 2 is a vertical end face, for example, by providing a phase grating on the end face, the propagating light 8 propagating in the mode on the Brillouin zone boundary is transmitted to the light output section 14. Can lead. Further, in the case of a waveguide element in which it is not necessary to take out the emitted light 6, it is not necessary to provide the light output unit 14. For example, in the case of a waveguide element in which incident light 5 is incident for use as control light or excitation light, the attenuation of energy of propagating light 8 may be significant. In such a case, it is not necessary to take out the emitted light 6, and therefore it is not necessary to provide the light output unit 14.

[0081] Each condition in the waveguide element 10a of the present embodiment may be obtained by band calculation.

[Third Embodiment]

A waveguide element according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 9 is a side view showing the configuration of the waveguide element according to Embodiment 3 of the present invention. In FIG. 9, members having the same functions as those shown in FIG. 2 are given the same reference numerals, and descriptions thereof are omitted.

As shown in FIG. 9, in the waveguide element 10b of the present embodiment, as in the case of the waveguide element 10 of the first embodiment, the propagating light 8 is reflected by the emission side inclined surface 2b. Then, it is emitted as outgoing light 6 through the substrate 1. However, unlike the case of the waveguide element 10 of the first embodiment, the incident light 5a is directly incident on the one-dimensional photonic crystal 2 from the incident side inclined surface 2a without passing through the substrate 1. Incident light 5 a incident on the one-dimensional photonic crystal 2 from the incident side inclined surface 2 a becomes propagating light 8 and propagates in the one-dimensional photonic crystal 2. In other words, in the waveguide element 10b shown in FIG. 9, the incident light 5a is emitted from the incident side inclined surface 2a directly into the one-dimensional photonic crystal 2 and the force-emitted light 6 is emitted through the substrate 1.

In the waveguide element 10b, as described above, the incident light 5a is directly incident on the one-dimensional photonic crystal 2 from the incident side inclined surface 2a without passing through the substrate 1. For this reason, the light input section 19 for making the incident light 5 a incident on the one-dimensional photonic crystal 2 faces the incident-side inclined surface 2 a. Are arranged. The light input unit 19 includes an optical fiber 19a, a collimator lens 19b, and an objective lens 19c.

Next, the operation of the waveguide element 10b according to the present embodiment will be described.

First, the incident light 5a propagating through the optical fiber 19a is collimated by the collimator lens 19b, then condensed by the objective lens 19c, and enters the photonic crystal 2 from the incident side inclined surface 2a. Incident. The propagating light 8 propagates through the one-dimensional photonic crystal 2 in the Z-axis direction. The propagating light 8 propagating in the one-dimensional photonic crystal 2 is preferably propagated by a mode on the Brillouin zone boundary in the photonic band structure.

[0087] The propagating light 8 propagating through the one-dimensional photonic crystal 2 in the Z-axis direction reaches the exit-side inclined surface 2b. The propagating light 8 is reflected by the outgoing inclined surface 2b and changes its course in the direction of the direction of force (Y-axis direction) on the bottom surface of the one-dimensional photonic crystal 2. Note that a reflective layer such as a metal film or a dielectric multilayer film may be provided on the outgoing side inclined surface 2b.

[0088] Further, the light that is reflected by the outgoing side inclined surface 2b of the one-dimensional photonic crystal 2 and becomes the outgoing light 6 is emitted from the bottom surface of the one-dimensional photonic crystal 2. The emitted light 6 from the one-dimensional photonic crystal 2 is incident on the substrate 1, propagates through the substrate 1, and is emitted from the substrate 1 to the outside. The emitted light 6 emitted from the substrate 1 is guided to the light output unit 4. Specifically, the outgoing light 6 emitted from the substrate 1 sequentially passes through the objective lens 4c and the collimating lens 4b and enters the optical fiber 4a. The light output unit 4 is arranged so that the emitted light 6 is guided to the light output unit 4 through the substrate 1.

The waveguide element 10b according to the present embodiment can achieve the same effects as the waveguide element 10 according to the first embodiment.

[0090] The one-dimensional photonic crystal 2 may not include the incident-side inclined surface 2a. Even if the end face on the incident side of the one-dimensional photonic crystal 2 is a vertical end face, the propagating light 8 can be a propagating light propagating by a mode on the Brillouin zone boundary. For example, a phase grating may be provided on the end face on the incident side of the one-dimensional photonic crystal 2 so that the incident light 5a is incident on the one-dimensional photonic crystal 2 via the phase grating. Further, in the case of a waveguide element that does not require incident light to enter, there is no need to provide the light input section 19. For example, a waveguide element that uses laser oscillation light generated by external energy as propagating light 8 In the case of a child, it is not necessary to provide the optical input unit 19.

[0091] Each condition in the waveguide element 10b of the present embodiment may be obtained by band calculation.

[0092] [Embodiment 4]

A waveguide element according to Embodiment 4 of the present invention will be described with reference to the drawings.

. FIG. 10 is a perspective view showing the configuration of the waveguide element in the fourth exemplary embodiment of the present invention.

[0093] The waveguide element 30 of the present embodiment and the waveguide element 10 of the first embodiment have substantially the same configuration except that the configuration of the one-dimensional photonic crystal is different. Therefore, in FIG. 10, members having the same functions as those shown in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted.

As shown in FIG. 10, the waveguide element 30 of the present embodiment includes a substrate 1, a one-dimensional photonic crystal 32 provided on the substrate 1, and light in the one-dimensional photonic crystal 32. And a light output unit 4 through which the light emitted from the one-dimensional photonic crystal 32 is guided.

The one-dimensional photonic crystal 32 is composed of a laminated structure in which two kinds of substances having different refractive indexes are periodically and alternately laminated in the Y-axis direction (the thickness direction of the substrate 1). The thickness of each material constituting the one-dimensional photonic crystal 32 is constant, and therefore the one-dimensional photonic crystal 32 has a refractive index periodicity only in one direction (Y-axis direction). Further, an incident side diffraction grating 32a and an emission side diffraction grating 32b are provided at both ends of the upper surface of the one-dimensional photonic crystal 32 (the surface on the opposite side of the substrate 1). Specifically, incident-side diffraction is formed by forming a plurality of grooves extending in the X-axis direction at equal intervals on the upper surface (a surface parallel to the XZ plane) of the one-dimensional photonic crystal 32 that is a laminated structure. A grating 32a and an output side diffraction grating 32b are provided.

[0096] Next, the operation of the waveguide element 30 of the present exemplary embodiment will be described.

First, the incident light 5 propagating through the optical fiber 3a is converted into parallel light by the collimator lens 3b, then condensed by the objective lens 3c, and incident on the substrate 1. The light from the light input unit 3 (incident light 5) propagates through the substrate 1 and then enters the bottom surface of the one-dimensional photonic crystal 32 (surface facing the top surface) into the one-dimensional photonic crystal 32. The 1D photonic crystal 32 The incident incident light 5 is reflected by the incident-side diffraction grating 32a, and from this, propagation light propagates in the one-dimensional photonic crystal 32 due to the mode on the Brillouin zone boundary in the photonic band structure. The propagating light is reflected by the exit-side diffraction grating 32b, and its path is changed to the bottom surface side (substrate 1 side) of the one-dimensional photonic crystal 32. The outgoing light 6 emitted from the bottom surface of the one-dimensional photonic crystal 32 passes through the substrate 1 and is guided to the light output unit 4.

The design of the entrance-side diffraction grating 32a and the exit-side diffraction grating 32b and the design of the one-dimensional photonic crystal 32 are performed using band calculation. This makes it possible to determine the conditions under which the propagating light propagates by the mode on the Brillouin zone boundary.

The one-dimensional photonic crystal 32 may include only one of the incident side diffraction grating 32a and the emission side diffraction grating 32b. In that case, the end face of the one-dimensional photonic crystal 32 on which the incident-side diffraction grating 32a or the emission-side diffraction grating 32b is not provided may be an inclined surface. Further, a phase grating may be provided on the end face of the one-dimensional photonic crystal 32, which is provided with the incident side diffraction grating 32a or the emission side diffraction grating 32b. This allows light to be incident into the one-dimensional photonic crystal 32 so that propagating light propagates depending on the mode on the Brillouin zone boundary. It can also be guided.

[0100] Next, a specific example in which an optical circuit using any one of the waveguide elements 10, 1 Oa, 10b, or 30 of Embodiment 1 to Embodiment 4 and an electronic circuit are combined will be described. To do. FIG. 11 is a perspective view showing a specific example in which an optical circuit using a waveguide element according to an embodiment of the present invention and an electronic circuit are combined.

As shown in FIG. 11, a lens array 41 in which a plurality of microlenses 4 la are arranged is arranged above the electronic circuit 42. Further, above the lens array 41, an optical circuit 40 including a waveguide element having the same function as the waveguide element of the first embodiment is disposed.

[0102] The upper surface of the electronic circuit 42 is provided with a VCSEL (Vertical Cavity Semiconductor Emission Laser) 42a and a light receiving cell 42b for emitting an optical signal in the vertical direction. Conductive wire 42c is provided for output.

[0103] Further, the optical circuit 40 is provided with a plurality of incident-side or emission-side inclined surfaces 40a. . Although not shown, the optical circuit 40 includes a one-dimensional photonic crystal, and the inclined surface 40a is formed in the one-dimensional photonic crystal. When light is incident on the inclined surface 40a, the light is propagated in the one-dimensional photonic crystal by a mode on the Brillouin zone boundary, and the light is emitted from the corresponding inclined surface 40a. Here, the microlens 41a corresponds to a light input unit or a light output unit.

For example, when an electric signal is input to the electronic circuit 42, signal light or control light is output from the VCSEL 42 a toward the lens array 41. The light 43 enters the inclined surface 40a through the microlens 41a. The signal light or the control light is processed by the waveguide element, and is emitted toward the lens array 41 from the inclined surface 40a different from the incident inclined surface 40a. The light 43 is input to the light receiving cell 42b through the microlens 41a.

[0105] With the configuration described above, the advantages of both flexible electronic processing and high-speed processing using light can be used. Further, according to the configuration shown in FIG. 11, since the optical circuit 40 and the electronic circuit 42 are arranged separately, the optical circuit 40 and the electronic circuit 42 are manufactured using completely different materials and processes. Can do. That is, the optical circuit 40 and the electronic circuit 42 can be efficiently manufactured without waste. Note that the optical circuit 40 and the electronic circuit 42 may be stacked and integrated on the same substrate.

Here, the optical circuit 40 provided with the waveguide element having the same function as the waveguide element of the first embodiment has been described as an example, but the second embodiment to the second embodiment are described. It may be provided with a waveguide element having the same function as the waveguide element of form 4

[Example]

The results of actually producing the waveguide device in the first embodiment and measuring the optical characteristics are shown below. FIG. 12 is a side view showing the configuration of the waveguide element in the example of the present invention. In FIG. 12, parts having the same functions as those shown in FIGS. 1 and 7 are given the same reference numerals.

First, the configuration of the waveguide element 50 of the present embodiment will be described.

[0109] The one-dimensional photonic crystal 2 that is the core of the waveguide is a Ta 2 O thin film and SiO 2 thin film formed on the upper surface of a parallel flat substrate 1 (100 mm X 20 mm X lmm) that also has quartz force by vacuum evaporation. Are alternately stacked. The thickness of the Ta O thin film is 424 nm, and Si

twenty five

The thickness of the O 2 thin film is 106 nm. These are the forces formed by 10 layers.

The thin film of 2 2 functions as the clad 51, and the film thickness is about 2000 nm. In other words, in this example, the SiO protection as the cladding 51 is formed on the one-dimensional photonic crystal 2 having the nine-layer structure.

Two layers are formed. From the above values, the refractive index period of the one-dimensional photonic crystal 2 is 530 η m. The optical characteristics were measured for two cases where the width (length in the X-axis direction) of the one-dimensional photonic crystal 2 was 10 mm and the length L of the one-dimensional photonic crystal 2 was 24.5 mm and 39.5 mm. went. In addition, both end surfaces of the one-dimensional photonic crystal 2 are cut obliquely so that the angles (tilt angles) formed by the XZ plane, the incident side inclined surface 2a, and the output side inclined surface 2b are 27 °, respectively. It is a polished surface. Further, reflective layers 21a and 21b made of silver having a thickness of 150 nm are formed on the incident side inclined surface 2a and the emission side inclined surface 2b by a vacuum deposition method, respectively.

[0110] The optical input unit 3 transmits incident light 5 propagating through an optical fiber 3a, which is a single-mode fiber for communication (SMF, wavelength 1550 nm specification, numerical aperture NA = 0. 1), with a focal length of 11.3 mm. The collimator lens 3b, which is a spherical lens, is converted into a parallel light beam. Further, the light input unit 3 transmits the parallel light beam by an objective lens 3c which is a cylindrical plano-convex lens (material is optical glass B K7, center thickness 3.8 mm, focal length 3.9 mm) having a curvature radius of 2. Omm. Convert to linear focus. This linear focal point is incident perpendicular to the bottom surface of the one-dimensional photonic crystal 2 (a plane parallel to the XZ plane). That is, the angle between the bottom surface of the one-dimensional photonic crystal 2 and the optical axis of the incident light 5 is 90 °. The focal point is linear because the one-dimensional photonic crystal 2 that becomes the core of the waveguide has a slab shape.

The light output unit 4 uses the same optical system as the light input unit 3 in reverse, and the light output unit 4 extracts the emitted light 6. Note that the band diagram of the one-dimensional photonic crystal 2 in this example has the shape shown in FIGS. 4 and 6 at a frequency corresponding to λ = 1550 nm.

0

It becomes a shape.

[0112] The SMFs (optical fibers 3a and 4a) on the incident side and the outgoing side are connected to an optical vector analyzer (OVA-CT type manufactured by Lun a Technologies Inc., USA), and the optical characteristics of the waveguide element 50 (JO All elements of the corn matrix were evaluated. [0113] The measurement results of this example are shown below.

FIG. 13 is a graph showing an impulse response when L = 24.5 mm in the present example. FIG. 14 is a graph showing an impulse response when L = 39.5 mm in this example. 13 and 14, the horizontal axis represents the delay time, and the vertical axis represents the amplitude. As shown in Fig. 13 and Fig. 14, it can be seen that in both cases, the force is such that the noise mode peak is slightly observed, and the propagation is almost a single mode (mode on the Brillouin zone boundary). Thus, according to the waveguide element 50 of the present embodiment, the mode on the Brillouin zone boundary can be propagated in a single mode.

FIG. 15 is a graph showing insertion loss when L = 24.5 mm in this example. FIG. 16 is a graph showing the insertion loss when L = 39.5 mm in this example. 15 and 16, the horizontal axis is wavelength and the vertical axis is insertion loss. As shown in Figure 15, the insertion loss at the peak wavelength when L = 24.5 mm is 19.8 dB. As shown in Fig. 16, the insertion loss at the peak wavelength when L = 39.5 mm is 28.7 dB.

In the present embodiment, the optical axes of the incident light 5 and the outgoing light 6 are set to be perpendicular to the substrate 1 (the substrate 1 for the incident light 5 and the outgoing light 6). It is possible to easily change the incident angle and the outgoing angle by changing the paths of the incident light 5 and the outgoing light 6.

Industrial applicability

According to the present invention, a waveguide element suitable for vertical coupling can be realized. Therefore, by mounting this waveguide element on an optical circuit and combining the optical circuit and the electronic circuit, a circuit that takes advantage of the advantages of the optical circuit and the electronic circuit can be manufactured.

Claims

The scope of the claims

[1] Refractive index periodicity in one direction, a bottom surface perpendicular to the direction having the refractive index periodicity, an incident side inclined surface and Z or exit inclined with respect to the bottom surface! A core photonic crystal having a side inclined surface;

A light input portion and a Z or light output portion arranged on the bottom surface side of the photonic crystal corresponding to the incident side inclined surface and Z or the outgoing side inclined surface,

The light input unit causes light to be incident on the photonic crystal through the bottom surface, and the light incident on the photonic crystal by the light input unit is reflected by the incident side inclined surface, and Propagation light is generated in the photonic crystal by a band on the Brillouin zone boundary,

The light output from the bottom surface of the photonic crystal is guided to the light output portion by the propagation light from the band on the Brillouin zone boundary propagating in the photonic crystal being reflected by the emission side inclined surface. Waveguide element to be cut.

[2] The waveguide element according to [1], wherein a reflection layer is formed on the incident side inclined surface and the Z or emission side inclined surface.

3. The waveguide element according to claim 2, wherein the reflective layer is made of a metal film or a dielectric multilayer film.

[4] A refractive index periodicity in one direction, a bottom surface perpendicular to the direction having the refractive index periodicity, a top surface facing the bottom surface, an incident-side diffraction grating provided on the top surface, and Z Or a photonic crystal as a core having an output side diffraction grating;

A light input unit and a Z or light output unit arranged on the bottom side of the photonic crystal corresponding to the incident side diffraction grating and the Z or output side diffraction grating,

The light input unit causes light to enter the photonic crystal through the bottom surface, and the light input into the photonic crystal by the light input unit is reflected by the incident-side diffraction grating, and Propagation light is generated in the photonic crystal by a band on the Brillouin zone boundary,

The light output from the bottom surface of the photonic crystal is guided to the light output part by propagating light from a band on the Brillouin zone boundary propagating in the photonic crystal by the output side diffraction grating. Waveguide element. The traveling direction of light incident into the photonic crystal and the traveling direction of light emitted from the Z or the photonic crystal are the same as the direction having the refractive index periodicity of the photonic crystal. Item 5. The waveguide device according to Item 1 or 4.