JP4468867B2 - Multilayer filter and optical wavelength filter having in-plane confinement structure - Google Patents

Description

  The present invention relates to a multilayer filter and an optical wavelength filter having an in-plane confinement structure. More specifically, the present invention relates to a multilayer filter inserted into a gap provided in an optical waveguide or an optical fiber on a flat substrate, and formed by the multilayer filter. The present invention relates to an optical wavelength filter.

  Currently, with the spread of the Internet and data communication, access networks are becoming faster and lighter. For example, in the B-PON system standardized by ITU-T recommendation G.983.1, as shown in FIG. 1, the communication from the subscriber 1 to the station 2 uses light having a wavelength of 1260-1360 nm, Communication from the station 2 to the subscriber 1 uses light having a wavelength of 1480 to 1580 nm, and it is determined that light in both wavelength bands is bidirectionally transmitted through the same optical fiber 3. In this case, it is necessary to multiplex and demultiplex the two lights by the filters 4 and 5 and transmit / receive them on the subscriber side and the station side.

In FIG. 1, an LD 6 that oscillates light having a wavelength λ ₁ (1260-1360 nm) and a PD 7 that receives light having a wavelength λ ₂ (1480-1580 nm) are connected to the filter 4. Therefore, the subscriber 1 transmits the light with the wavelength λ ₁ to the station 2 and receives the light with the wavelength λ ₂ . On the other hand, the filter 5 is connected to an LD 8 that oscillates light of wavelength λ ₂ and a PD 9 that receives light of wavelength λ ₁ . Therefore, the station 2 transmits the light having the wavelength λ ₂ to the subscriber 1 and receives the light having the wavelength λ ₁ .

An example of an optical transmission / reception module for this purpose is shown in Patent Document 1. As in the optical module described in Patent Document 1, a WDM optical transmission / reception module in which LD, PD, and a multilayer filter are hybrid-mounted on a planar optical waveguide is being developed actively because it can be made small and inexpensive. .
Recently, as shown in FIG. 2, a system for providing a service by superimposing an additional signal on another wavelength to a desired subscriber has been studied. In FIG. 2, the subscriber 21 includes a filter 24. The filter 24, the LD26 for oscillating light of a wavelength lambda _1, the PD27 for receiving the light of the wavelength lambda _2, the PD28 for receiving the light of wavelength λ ₃ (1550-1560nm) is connected. On the other hand, the station 22 includes a filter 25. The filter 25, the LD29 for oscillating the light of the wavelength lambda _2, the LD30 for oscillating light of wavelength lambda _3, and PD31 are connected for receiving the light of wavelength lambda _1.

  In FIG. 2, with such a configuration, signal exchange between the subscriber 21 and the station 22 is performed via the optical fiber 23.

  Thus, the form of providing different services at different wavelengths is increasing, and the number of wavelengths is expected to increase. Patent Document 1 describes a method of multiplexing and demultiplexing light of different wavelengths with a multilayer filter inserted in an optical waveguide. This system does not require a lens or the like, and is a compact optical component suitable for integration and mass production.

JP-A-11-68705

However, a problem arises when the method described in Patent Document 1 is applied to the system shown in FIG. In the system shown in FIG. 1, there is a 120 nm guard band between the wavelengths λ ₁ and λ ₂ of the light multiplexed / demultiplexed by the multilayer filter. Therefore, the multilayer filter may be manufactured so that the transmission and reflection characteristics are switched in this guard band, and a good optical transceiver module with small crosstalk can be realized.

However, in the system shown in FIG. 2, there is only a 50 nm guard band between wavelengths λ ₂ and λ ₃ . Further, in the future, when a wavelength different from the above-described wavelengths λ _{1 to} λ ₃ is used, the guard band wavelength may become narrower. When the guard band is 50 nm or less, the cutoff characteristic of the membrane filter is somewhat insufficient, the two lights incident on the multilayer filter cannot be sufficiently demultiplexed, and crosstalk may occur. As a result, there arises a problem that the operation of the optical transceiver module becomes unstable.

  The present invention has been made in view of such problems, and the object of the present invention is that the cutoff wavelength characteristic of a multilayer filter inserted into an optical waveguide without using a lens is not sufficiently steep. An object of the present invention is to provide a multilayer filter and an optical wavelength filter having an in-plane confinement structure that solves the problem and realizes an optical transceiver module with reduced crosstalk.

  In order to achieve the above object, the present invention provides a multilayer film formed by laminating a substrate and at least two types of optical thin films formed on the substrate in multiple layers. The at least one optical thin film has an in-plane refractive index in which the refractive index of a predetermined region is higher than the refractive index around the predetermined region in at least one in-plane direction of the optical thin film. A multilayer film having a distribution, and at least a light incident on a region where the in-plane refractive index distribution is formed at a predetermined angle with respect to a vertical direction of the substrate is confined in the multilayer film and the multilayer film It is characterized by propagating through the film.

  According to a second aspect of the present invention, in the first aspect of the invention, the in-plane refractive index distribution is such that a region having a higher refractive index than the periphery of the predetermined region is centered on a predetermined point in the predetermined region. It is characterized by the two-dimensional distribution.

  According to a third aspect of the present invention, in the first aspect of the invention, the in-plane refractive index distribution is such that a region having a higher refractive index than the periphery of the predetermined region is a linear one-dimensional distribution. It is characterized by.

  According to a fourth aspect of the present invention, the multilayer filter according to the second aspect of the present invention and a cross-type optical waveguide are provided, and a direction substantially perpendicular to the longitudinal direction of the waveguide core of the optical waveguide at the intersection of the optical waveguide. The multilayer filter is inserted into the groove so that the predetermined region of the multilayer filter and the waveguide core substantially coincide with each other.

  According to a fifth aspect of the present invention, the multilayer filter according to the third aspect of the present invention and an intersecting optical waveguide are provided, and at a crossing portion of the optical waveguide, a direction substantially perpendicular to the longitudinal direction of the waveguide core of the optical waveguide And the width of the waveguide core in the vicinity of the intersection is wider than the width of the waveguide core other than in the vicinity of the intersection, the height of the waveguide core, and the predetermined region The multilayer filter is inserted in the width so that the height of the filter substantially coincides.

  As described above, according to the present invention, in a multilayer film formed by laminating at least two types of optical thin films, at least one of the optical thin films is in at least one in-plane direction of the optical thin film. Since the refractive index of the predetermined region has an in-plane refractive index distribution that is higher than the refractive index around the predetermined region, a steep cutoff wavelength characteristic can be realized without using a lens, An optical module with reduced crosstalk can be realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings described below, components having the same function are denoted by the same reference numerals, and repeated description thereof is omitted.
First, the reason why the cutoff wavelength characteristic of the multilayer filter inserted in the optical waveguide is not sufficiently steep is analyzed. FIG. 3 shows an example of a cutoff wavelength characteristic when a multilayer filter is inserted into a light beam collimated using a lens in space. In FIG. 3, two wavelength spectra correspond to a transmission spectrum and a reflection spectrum. In this case, a steep cutoff wavelength characteristic is shown, and it can be seen that the transmission and reflection characteristics are switched in a guard band of about 4 nm.

  Next, FIG. 4 shows the cutoff wavelength characteristics when the multilayer filter is inserted into the optical waveguide. In FIG. 4, two wavelength spectra correspond to a transmission spectrum and a reflection spectrum. FIG. 4 shows that the cut-off wavelength characteristic is greatly reduced compared to FIG.

  The cause of the loss of the cutoff wavelength characteristic can be considered as follows. The light that is collimated and is in a state close to a plane wave realizes a strong resonance state without being dissipated no matter how many times it is reflected by the resonator in the multilayer film. On the other hand, when a multilayer filter is inserted into the waveguide, light is diffracted and dissipated in the multilayer film, so that a strong resonance state cannot be realized. Therefore, in order to realize a steep wavelength characteristic as shown in FIG. 3 with the multilayer filter inserted in the waveguide, it is only necessary to realize a state close to a collimated beam by expanding the beam size. Regarding the beam size in the planar optical waveguide, the beam size in the horizontal direction with respect to the substrate can be easily increased by increasing the core width.

  However, enlarging the beam size in the direction perpendicular to the substrate is burdensome in terms of process. Specifically, the beam size in the direction perpendicular to the substrate can be increased by increasing the core thickness at the portion intersecting the multilayer filter. However, depositing a thick core and forming a taper in the height direction on the core imposes a heavy burden on the manufacturing process and increases the manufacturing cost. Therefore, in one embodiment of the present invention, a high resonance state is realized by creating an optical confinement structure in the multilayer filter instead of expanding the beam size in the optical waveguide.

(First embodiment)
FIG. 5 shows a multilayer filter having a two-dimensional in-plane refractive index distribution according to the first embodiment of the present invention. In FIG. 5, two in-plane directions of the polyimide substrate 51 and the multilayer film 52 are the x and y axis directions, and the height direction is the z axis direction.

  A thin polyimide film is used as the substrate of the multilayer filter 50 according to the present embodiment. This is because the multilayer filter 50 according to the present embodiment is assumed to be used by being inserted into a waveguide without using a lens. Therefore, in order to suppress diffraction loss at that time, several μm The polyimide film that can realize the thickness is used. The polyimide film thickness of this embodiment is 5 μm.

A SiO ₂ / Ta ₂ O ₅ multilayer film 52 is formed on a polyimide substrate 51 made of such a polyimide film. As the multilayer film 52, a laminated film of commonly used SiO ₂ and Ta ₂ O ₅ is used. The multilayer film 52 is deposited on the polyimide substrate 1 by ion-assisted vacuum evaporation. The film thickness of the multilayer film 52 is 20 μm. After the multilayer film 52 is deposited, a predetermined region on the upper surface of the multilayer film 52 is irradiated with ultraviolet rays to form a high refractive index region 53 that is a region having a higher refractive index than the surroundings, and the multilayer film 52 An in-plane (x, y-axis direction) refractive index distribution is formed.

In the present embodiment, the multilayer film 52 is formed by laminating two types of optical thin films of SiO ₂ and Ta ₂ O ₅ , but the present invention is not limited to this. That is, the composition of the material and the number of materials to be laminated are not essential, and it is important to form an in-plane confinement structure by providing the multilayer film 52 with a region having a higher refractive index than the periphery thereof, as will be described later. is there. Therefore, other optical thin films may be used as a material for forming the multilayer film 52, and the number of optical thin films may be at least two kinds.

6A and 6B show the refractive index distribution of the multilayer filter according to the present embodiment. FIG. 6A is a diagram showing an in-plane refractive index distribution of the Ta ₂ O ₅ layer according to this embodiment, and FIG. 6B is an internal refractive index of the SiO ₂ layer according to this embodiment. FIG. 6C is a diagram showing the refractive index distribution in the film thickness direction (z-axis direction) of the multilayer film.

In the present embodiment, in-plane refractive index distributions are formed on both the SiO ₂ layer and the Ta ₂ O ₅ layer included in the multilayer film 52 by ultraviolet irradiation. Regarding the SiO ₂ and Ta ₂ O ₅ layers, the difference in refractive index between the UV-irradiated place and the surrounding area is 0.5% for the Ta ₂ O ₅ layer and 0.1% for the SiO ₂ layer, and there is a difference between them. Has occurred. This in-plane refractive index distribution is formed for the purpose of confining light incident substantially perpendicularly to the multilayer film in the in-plane direction, and therefore functions even if it is formed only in at least one of the two layers. To do.

Moreover, even if there is a difference in refractive index between the SiO ₂ layer and the Ta ₂ O ₅ layer as in the present embodiment, it functions. Furthermore, the in-plane refractive index of the SiO ₂ layer and the Ta ₂ O ₅ layer may be a rectangular refractive index distribution shown in FIGS. 6A and 6B, or may be a mountain-shaped gentle refractive index distribution. Absent. What is important in this embodiment is that the mode field of light confined in the in-plane direction of the SiO ₂ layer / Ta ₂ O ₅ layer is close to the mode field of the optical waveguide used for input and output.

  In the present embodiment, the portion having a high refractive index is formed obliquely in the depth direction (z-axis direction) of the multilayer filter 50 in accordance with the incident angle of light 6 ° in FIG. 8 described later. The ultraviolet rays are irradiated from the vertical direction in the plane of the multilayer film 52 at an incident angle of 6 °.

  The multilayer filter 50 in which the in-plane refractive index distribution as described above is formed is finally cut into chips with a dicing saw. The multilayer filter chip is finally inserted into a groove provided in the optical waveguide. At that time, it is important to align the core of the optical waveguide with the high refractive index region 53 of the multilayer film 52 (the portion where the refractive index of the multilayer film 52 is high).

  For this reason, in the present embodiment, two ideas have been made. FIG. 7 is a plan view of a multilayer filter chip for explaining this device. The first idea is to cut the chip so that the distance from the end of the chip to the high refractive index region 53 becomes a predetermined value when the multilayer filter 50 is cut into the chip. Here, the predetermined value means the distance from the bottom of the groove for inserting the chip provided in the optical waveguide to the core of the optical waveguide. In addition, the groove | channel for inserting a chip | tip is formed so that the core of a waveguide may be penetrated.

  When the multilayer filter chip 71 formed in this way is inserted into the groove for inserting the chip, the end of the chip 71 is abutted against the groove, so that the core and the high refractive index region 53 in the height direction automatically. Alignment is realized. Specifically, in this embodiment, the depth of the groove for inserting the chip from the upper surface of the optical waveguide is 150 microns, and the depth of the core from the upper surface of the optical waveguide is 25 microns. Therefore, the height from the bottom of the groove to the core is 125 microns. Therefore, the distance from the end of the multilayer filter chip 71 (the side in contact with the groove) to the high refractive index region 53 is designed to be 125 microns.

  The second contrivance is to form a hole as a mark by strongly applying the same ultraviolet ray in the vicinity thereof when the high refractive index region 53 is formed with the ultraviolet ray. In this embodiment, the hole is formed at the end of the chip 71 by strongly irradiating ultraviolet rays near the high refractive index region 53. In the present embodiment, this hole is used as a marker (alignment marker), thereby aligning the high refractive index region 53 and the core. In FIG. 7, markers 72a and 72b are formed as such positioning markers. The marker used at the time of actual alignment is the marker 72a. The marker 72b is formed when a marker for alignment is formed on a chip adjacent to the chip 71 on the side where the high refractive index region 53 is formed.

  8 is a perspective view of the multiplexer / demultiplexer in which the multilayer filter chip is inserted into the optical waveguide, FIG. 9 is a top view of the multiplexer / demultiplexer shown in FIG. 8, and FIG. It is AA 'line cutting | disconnection sectional drawing of.

  8 to 10, the multiplexer / demultiplexer 81 includes a silicon substrate 82, a clad 83 formed on the silicon substrate 81, and a Y-branch waveguide core 84 embedded in the clad 83. One output end branched into two of the Y-branch type waveguide core 84 is a reflection port 87, and the other output end is a common port 88. Further, the non-branched output end of the Y-branch waveguide core 84 is a transmission port 89.

  An insertion groove 85 for inserting a chip is formed on the upper surface side (cladding 83) of the multiplexer / demultiplexer 81 at a branch point of the waveguide core 84 in a direction substantially perpendicular to the longitudinal direction of the waveguide core 84. Yes. The depth of the insertion groove 85 is set so as to penetrate the waveguide core 84 from the top surface of the clad 83 and the bottom surface 86 of the groove is at a distance d from the waveguide core 84.

  In the insertion groove 85, a multilayer filter chip 71 in which the distance from the end surface on the insertion side to the high refractive index region 53 is set to the distance d is inserted. The multilayer filter chip 71 is positioned by a positioning marker 72a. That is, in the multilayer filter chip 71, since the marker 72a is formed vertically above the high refractive index region 53, the chip 71 is moved in the insertion groove 85 so that the marker 72a is aligned with the waveguide core 84. If the positioning is performed, the waveguide core 84 and the high refractive index region 53 can be positioned in the substrate in-plane direction with high accuracy. Further, since the distance from the end surface on the insertion side of the chip 71 to the high refractive index region 53 and the distance from the waveguide core 84 to the bottom surface 86 of the groove are set to the distance d, the waveguide core 84 and the high refractive index are set. Positioning in the height direction with the rate region 53 can also be performed with high accuracy.

  After positioning the waveguide core 84 and the high refractive index region 53, the multilayer filter chip 71 is fixed with an adhesive. Thus, the optical wavelength filter is formed by inserting the multilayer filter chip into the optical waveguide. At this time, as can be seen from FIGS. 8 to 10, in this embodiment, no lens is provided between the multilayer filter chip 71 and the waveguide core 84.

  In the present embodiment, light incident on the multilayer filter chip 71 from the waveguide core 84 is incident on the high refractive index region 53. Therefore, in the multilayer filter chip 71, light is confined by the high refractive index region, so that a high resonance state can be realized. Therefore, it is possible to improve the steepness of the cutoff wavelength characteristic of the multilayer filter.

  In the multiplexer / demultiplexer having such a configuration, a transmission wavelength spectrum from the common port 88 to the transmission port 89 and the reflection port 87 is shown in FIG. In this embodiment, as shown in FIG. 11, it can be seen that the cut-off wavelength characteristics are steeper than in the case of using the multilayer filter having no in-plane refractive index distribution of FIG. It is also possible to make the cutoff wavelength characteristic steep by optimizing the in-plane refractive index distribution.

  As described above, by using the multilayer filter according to the present embodiment, an integrated multiplexing / demultiplexing filter having a steep cutoff wavelength characteristic can be realized without providing a lens between the multilayer filter and the optical waveguide. be able to.

(Second Embodiment)
FIG. 12 shows a multilayer filter having a one-dimensional in-plane refractive index distribution according to the second embodiment of the present invention. The multilayer filter 120 according to the present embodiment has basically the same configuration as the multilayer filter 50 used in the first embodiment. The difference between the two is that the shape of the portion having a high refractive index in the multilayer film 52 has a two-dimensional distribution in the first embodiment, whereas in this embodiment, as shown in FIG. This is a point having a one-dimensional distribution on a straight line. That is, as shown in FIG. 12, the high refractive index region 121, which is a region having a higher refractive index than the surrounding area, is in the horizontal direction with respect to the substrate in the vertical plane of the substrate when the multilayer filter is inserted into the optical waveguide. And has a refractive index component. FIG. 13 shows a top view of a multilayer filter having a one-dimensional refractive index distribution in this way. Other methods for increasing the film thickness, refractive index, and the like are the same as those in the first embodiment, and thus description thereof is omitted.

  In the configuration of the multilayer filter 120 of the present embodiment, since there is no lateral confinement, alignment in the lateral direction (in the x-axis direction in FIG. 12) becomes unnecessary when the multilayer filter is inserted into the intersecting waveguide. The filter insertion work is greatly reduced. What is important in the present embodiment is that the distance from the bottom surface of the groove for inserting the chip to the waveguide core is the only thing in order to align the waveguide core and the high refractive index region 121 with high accuracy. The distance from the end on the insertion side to the groove of the multilayer filter to the high refractive index region 121 needs to be the same.

  However, in this embodiment, there is a confinement effect in the vertical direction (y-axis direction in FIG. 12), but no confinement effect in the horizontal direction (x-axis direction in FIG. 12). Therefore, it is difficult to suppress lateral diffraction in this state. Therefore, in the present embodiment, in the waveguide core of the optical waveguide portion where the multilayer filter 120 is inserted, the width of the waveguide core is made larger than the width of the waveguide core other than the connection portion of the waveguide core. FIG. 14A is a top view showing the vicinity of the connection portion between the waveguide core and the high refractive index region according to the present embodiment, and FIG. 14B is a cross-sectional view taken along line BB ′ of FIG. FIG.

  As shown in FIG. 14A, in this embodiment, the waveguide core 141 has a tapered waveguide core 142 at the connection portion between the waveguide core 141 and the high refractive index region 143 of the multilayer filter. That is, in the waveguide core, the width of the waveguide core in the vicinity of the connection portion with the high refractive index region 143 is made wider than the width of the other waveguide cores, thereby reducing the width of the waveguide core in the connection portion. Further, the width of the waveguide core is made wider than that of the other waveguide cores to suppress diffraction in the width direction of the waveguide cores (the x-axis direction in FIG. 12). Further, as shown in FIG. 14B, the width of the tapered waveguide core 142 is wider than its height. Usually, the width of the waveguide core is about several microns. In this case, the width of the waveguide core of the connecting portion may be about 20 to 30 microns.

  In this embodiment, the multilayer filter 120 is irradiated with ultraviolet rays in a wafer state to form a one-dimensionally high refractive index portion, and the high refractive index region 121 is formed in the multilayer film 52. Then, it cuts out into a multilayer filter chip with a dicing saw. At the time of this cutting, cutting is performed so that the distance from the end of the multilayer filter chip on the insertion side to the groove to the high refractive index region 121 matches the distance from the groove bottom surface for inserting the chip to the waveguide core. . By cutting the multilayer filter 120 in such a manner, the high refractive index region 121 is in the lateral direction in the plane of the chip (longitudinal direction of the groove for inserting the chip) just by inserting the multilayer filter chip into the groove. Therefore, the waveguide core and the high refractive index region 121 of the multilayer filter chip can be aligned in the height direction.

  FIG. 14 shows a transmission wavelength spectrum from the common port to the transmission port and the reflection port when the multilayer filter chip according to the present embodiment is inserted into the multiplexer / demultiplexer configured as shown in FIG. As can be seen from FIG. 15, in this embodiment, the cut-off wavelength characteristic is sharper than the transmission spectrum of the prior art shown in FIG.

It is a figure which shows an example of the conventional optical access system. It is a figure which shows an example of the conventional optical access system. It is a figure which shows an example of the cutoff wavelength characteristic at the time of inserting a multilayer filter in the light beam collimated using the lens in space. It is a figure which shows an example of the cutoff wavelength characteristic when a multilayer filter is inserted in an optical waveguide. It is a figure which shows the multilayer filter based on one Embodiment of this invention. (A), according to an embodiment of the present invention is a diagram showing an in-plane refractive index distribution of the Ta ₂ O ₅ layer, (b), according to an embodiment of the present invention, the surface of the SiO ₂ layer It is a figure which shows an internal refractive index distribution, (c) is a figure which shows the refractive index distribution of the film thickness direction of a multilayer film. It is a top view of the multilayer filter chip for demonstrating alignment with the core of an optical waveguide, and the high refractive index area | region of a multilayer film based on one Embodiment of this invention. 1 is a perspective view of a multiplexer / demultiplexer in which a multilayer filter chip is inserted into an optical waveguide according to an embodiment of the present invention. FIG. 9 is a top view of the multiplexer / demultiplexer shown in FIG. 8. FIG. 10 is a cross-sectional view taken along line A-A ′ of FIG. 9. It is a figure which shows the transmission wavelength spectrum from the common port to the transmission port and reflection port based on one Embodiment of this invention. It is a figure which shows the multilayer filter based on one Embodiment of this invention. It is a figure showing the upper surface of a multilayer filter concerning one embodiment of the present invention. (A) is a top view which shows the connection part vicinity of a waveguide core and high refractive index area | region based on one Embodiment of this invention, (b) is a BB 'line | wire cross section of (a). FIG. It is a figure which shows the transmission wavelength spectrum from the common port to the transmission port and reflection port based on one Embodiment of this invention.

Explanation of symbols

51 Polyimide substrate 52 Multilayer film 53 High refractive index region

Claims (2)

A substrate,
A multilayer film formed on the substrate by laminating at least two types of optical thin films in multiple layers, wherein at least one of the optical thin films is a predetermined region in the in-plane direction of the optical thin film Has an in-plane refractive index distribution higher than the refractive index around the predetermined region, and the in- plane refractive index distribution is a two-dimensional centered on a predetermined point in the predetermined region. A multilayer filter having a multilayer film having an in-plane refractive index distribution ;
With a crossed optical waveguide,
In the multilayer filter, light incident on at least a region where the in-plane refractive index distribution is formed at a predetermined angle with respect to a vertical direction of the substrate is confined in the multilayer film and passes through the multilayer film. have a plane confinement structure you propagation,
At the intersection of the optical waveguide, a groove is formed in a direction substantially perpendicular to the longitudinal direction of the waveguide core of the optical waveguide,
The optical wavelength filter, wherein the multilayer filter is inserted into the groove so that the predetermined region of the multilayer filter and the waveguide core substantially coincide with each other . A substrate,
A multilayer film formed on the substrate by laminating at least two types of optical thin films in multiple layers, wherein at least one of the optical thin films is a predetermined region in the in-plane direction of the optical thin film the refractive index has a plane refractive index distribution higher than the refractive index of the periphery of the predetermined region, the plane refractive index profile of the multilayer film is a one-dimensional in-plane refractive index distribution of the linear A multilayer filter having ,
With a crossed optical waveguide,
In the multilayer filter, light incident on at least a region where the in-plane refractive index distribution is formed at a predetermined angle with respect to a vertical direction of the substrate is confined in the multilayer film and passes through the multilayer film. have a plane confinement structure you propagation,
At the intersection of the optical waveguide, a groove is formed in a direction substantially perpendicular to the longitudinal direction of the waveguide core of the optical waveguide,
The width of the waveguide core in the vicinity of the intersection is wider than the width of the waveguide core other than in the vicinity of the intersection,
The optical wavelength filter, wherein the multilayer filter is inserted in the width so that a height of the waveguide core and a height of the predetermined region substantially coincide with each other .

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