JP2008241952A - Wavelength selection reflection circuit and multiwavelength light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength selection reflection circuit capable of easily forming wavelength selection reflection parts having a desired wavelength without using a phase grating mask and to provide a multiwavelength light source provided with the wavelength selection reflection circuit. <P>SOLUTION: The wavelength selection reflection circuit 100 of a polymer resin is provided with a main line part 112 having an input/output end 114 through which an optical signal is input/output and which is formed on one end of the main line part, optical waveguide 110 having seven sub line parts 116 coupled to the main line part 112 via optical directional coupling circuits 118 and the wavelength selection reflection parts 130 formed on the main line part 112 and the sub line parts 116 and having reflection wavelengths different from each other. Heaters 120 switching whether the optical signal is coupled from the main line part 112 to the sub line parts 116 via the optical directional coupling circuits 118 by heating the optical directional coupling circuits 118 are formed on the wavelength selection reflection circuit 100. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wavelength selective reflection circuit that reflects an optical signal, and more particularly to a wavelength selective reflection circuit having a diffraction grating formed by a two-beam interference exposure method using ultraviolet rays. The present invention also relates to a multiwavelength light source including the wavelength selective reflection circuit.

Conventionally, an optical circuit in which a diffraction grating is formed has been widely used. As a method of forming a diffraction grating in an optical circuit, for example, there is a phase grating method in which hydrogen is penetrated into an optical circuit and ultraviolet rays are irradiated through a phase grating mask to form a diffraction grating (see, for example, Patent Document 1). reference.).
JP 2004-233665 A

  In the phase grating method, it is necessary to prepare a phase grating mask having a pattern corresponding to the diffraction grating, and there is a problem that the diffraction grating cannot be easily formed. On the other hand, it is also possible to form a diffraction grating by directly irradiating an optical circuit with ultraviolet rays without using a phase grating mask. However, in order to form a diffraction grating having a desired reflection wavelength, it is necessary to precisely control the irradiation position and irradiation direction of ultraviolet rays, and there is a problem that the diffraction grating cannot be easily formed.

  An object of the present invention is to provide a wavelength selective reflection circuit capable of easily forming a wavelength selective reflection portion having a desired reflection wavelength without using a phase grating mask, and a multiwavelength light source including the wavelength selective reflection circuit. And It is another object of the present invention to provide a wavelength selective reflection circuit capable of taking a wavelength tuning width per 1 ° C. larger than a quartz optical waveguide, and a multiwavelength light source including the wavelength selective reflection circuit.

  The wavelength selective reflection circuit according to the present invention is characterized in that wavelength selective reflection portions having different reflection wavelengths are formed in a polymer optical waveguide.

  Specifically, the wavelength selective reflection circuit according to the present invention is coupled to the main line portion via a main line portion formed at one end and an optical directional coupling circuit with an input / output end for inputting / outputting an optical signal. The optical directional coupling to a wavelength selective reflection circuit of a polymer resin comprising: an optical waveguide having one or more branch line parts; and a wavelength selective reflection part formed on the main line part and the branch line part and having different reflection wavelengths. A heater is formed that switches whether the optical signal is coupled to the branch line portion from the main line portion via the optical directional coupling circuit by heating the circuit.

  The wavelength selective reflection circuit according to the invention can easily form a wavelength selective reflection portion having a desired reflection wavelength without using a phase grating mask. In addition, the wavelength selective reflection circuit according to the invention can have a larger wavelength tuning width per 1 ° C. than a quartz optical waveguide.

  In the wavelength selective reflection circuit according to the present invention, it is preferable that the wavelength selective reflection portion is a diffraction grating having different refractive indexes and having gratings formed in the same direction.

  Since the wavelength selective reflection circuit according to the invention has the same grating direction, the wavelength selective reflection part can be formed more easily.

  A multi-wavelength light source according to the present invention is a multi-wavelength light source comprising: a wavelength selective reflection circuit according to the present invention; and a semiconductor laser light source coupled to the input / output end of the main line portion of the wavelength selective reflection circuit. The wavelength range in which the semiconductor laser light source can oscillate includes the reflection wavelength of the wavelength selective reflection portion.

  The multi-wavelength light source according to the invention can easily form a wavelength selective reflection portion having a desired reflection wavelength without using a phase grating mask. In addition, the multi-wavelength light source according to the invention can have a larger wavelength tuning width per 1 ° C. than a quartz optical waveguide.

  The present invention can provide a wavelength selective reflection circuit capable of easily forming a wavelength selective reflection portion having a desired reflection wavelength without using a phase grating mask, and a multi-wavelength light source including the wavelength selective reflection circuit. . In addition, it is possible to provide a wavelength selective reflection circuit capable of taking a wavelength tuning width per 1 ° C. larger than that of a quartz optical waveguide, and a multiwavelength light source including the wavelength selective reflection circuit.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment. Moreover, the same code | symbol was attached | subjected to the same member and the same site | part.

(First embodiment)
FIG. 1 shows a top view of the wavelength selective reflection circuit according to the first embodiment. The wavelength selective reflection circuit 100 according to the first embodiment is coupled to the main line portion 112 via the main line portion 112 and the optical directional coupling circuit 118 in which an input / output end 114 for inputting / outputting an optical signal is formed at one end. In the wavelength selective reflection circuit 100 made of polymer resin, including the optical waveguide 110 having the seven branch line portions 116, and the wavelength selective reflection portion 130 formed on the main line portion 112 and the branch line portion 116 and having different reflection wavelengths. By heating the optical directional coupling circuit 118, a heater 120 is formed that switches whether the optical signal is coupled to the branch line part 116 from the main line part 112 via the optical directional coupling circuit 118. Further, FIG. 1 shows a grating 132.

  The wavelength selective reflection circuit 100 is, for example, a polymer resin such as polysilane, polyimide, polymethyl methacrylate (PMMA), polystyrene (PS). The wavelength selective reflection circuit 100 includes, for example, one main line portion 112 and seven branch line portions 116, but the number of main line portions 112 and branch line portions 116 is not limited.

  At the place where the branch line part 116 is coupled to the main line part 112, the same number of optical directional coupling circuits 118 as the number of branch line parts 116, for example, seven, are formed. In the optical directional coupling circuit 118, the branch line part 116 and the main line part 112 are formed in parallel at a predetermined interval, for example, 1 to 10 μm, and the main line part 112 is utilized by using distributed coupling of optical signals propagating through the main line part 112. Is coupled to the branch line portion 116.

  The heater 120 is formed so that the branch line portion 116 is sandwiched between the optical directional coupling circuit 118 and the heater 120 when the surface of the optical waveguide 110, for example, the wavelength selective reflection circuit 100 is viewed from above. The heater 120, for example, plating a metal film such as Al, Cu, Cr or the like or bonding a metal plate with an adhesive, generates heat by a current from a power source (not shown), and heats the optical directional coupling circuit 118. For example, when the heater 120 is heating the branch line part 116 and the optical directional coupling circuit 118, an optical signal is coupled from the branch line part 116 to the main line part 112, and the heater 120 is not heating the light directional coupling circuit 118. When the optical signal propagates through the branch line part 116. On the other hand, when the heater 120 is located on the main line portion 112 side and is heating the main line portion 112 and the optical directional coupling circuit 118, the optical signal propagates through the branch line portion 116, and the heater 120 is in the light directional coupling circuit 118. The optical signal may be coupled from the branch line portion 116 to the main line portion 112 when the heater is not heated.

  The reflection wavelengths of the eight wavelength selective reflection units 130 are, for example, 1535 nm, 1540 nm, 1545 nm, 1550 nm, 1555 nm, 1560 nm, 1565 nm, and 1570 nm. The wavelength selective reflection circuit 100 preferably includes a control circuit (not shown) that controls whether or not the heater 120 is heated so that the optical signal reaches the wavelength selective reflection unit 130 having a desired reflection wavelength. . The wavelength selective reflection circuit 100 can easily select the reflection wavelength by the control circuit.

  In the wavelength selective reflection circuit 100 according to the first embodiment, the wavelength selective reflection unit 130 is preferably a diffraction grating having a refractive index and a grating 132 formed in the same direction. The diffraction grating includes, for example, four gratings 132, but the number of the gratings 132 is not limited. The wavelength selective reflection unit 130 is formed away from the end face on the input / output end 114 side, but may be on the main line part 112 or the branch line part 116. Here, the interval between the gratings 132 is, for example, 0.45 to 0.55 μm when the reflection wavelength is in the 1550 nm band. Furthermore, as shown in FIG. 1, in the wavelength selective reflection circuit 100 according to the first embodiment, it is preferable that the diffraction gratings have substantially the same distance from the end face on the input / output end 114 side. Thereby, the wavelength selective reflection circuit 100 can form the wavelength selective reflection unit 130 more easily. The reason will be described later.

  In the case where the wavelength selective reflection circuit 100 is polysilane, for example, when a wavelength selective reflection portion heating means (not shown) made of a metal such as Cr is further formed on the surface of the over clad where the wavelength selective reflection portion 130 is formed, the temperature is increased. It can be changed in the range of 20 to 80 ° C., and wavelength control of 4 to 6 nm is possible.

  The wavelength selective reflection circuit 100 uses, for example, a semiconductor laser light source (not shown) coupled to the input / output end 114.

  FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. The optical waveguide 110 is made of polymer resin, and includes, for example, an over clad layer 122, an under clad layer 124, and a core layer 126 composed of a main line portion 112 and a branch line portion 116 formed in the over clad layer 122 and the under clad layer 124. Have The core layer 126 has a higher refractive index than the over clad layer 122 and the under clad layer 124. The refractive index difference between the core layer 126, the over clad layer 122, and the under clad layer 124 is, for example, 0.3 to 7%. In FIG. 2, the boundary lines of the over clad layer 122, the under clad layer 124, and the core layer 126 are shown by broken lines for the sake of explanation.

  The optical waveguide 110 is laminated on the substrate 91, for example. The substrate 91 is, for example, a silicon substrate, a quartz glass substrate, or a sapphire substrate. In consideration of the heating of the heater 120, the substrate 91 may be a polymer resin. If the substrate 91 is made of a polymer resin, the difference in thermal expansion coefficient between the substrate 91 and the optical waveguide 110 is reduced, and damage to the wavelength selective reflection circuit 100 and peeling of the optical waveguide 110 can be reduced.

  The manufacture of the wavelength selective reflection circuit 100 will be described. The wavelength selective reflection circuit 100 can be manufactured using, for example, a laser direct exposure method or a photolithography method. When the laser direct exposure method is used, for example, the under cladding layer 124 and the core layer 126 are sequentially stacked on the substrate 91. For example, in the case of polysilane, the core layer 126 is irradiated with ultraviolet rays through a photomask in which a pattern is formed so that the main line portion 112 and the branch line portion 116 are not irradiated with ultraviolet rays. The refractive index of the portion of the core layer 126 irradiated with ultraviolet rays is lowered by the irradiation of ultraviolet rays, and the main line portion 112 and the branch line portion 116 can be formed in the core layer. Next, a diffraction grating (not shown) is formed as the wavelength selective reflection unit 130, and then, for example, an over cladding layer 122 is laminated. The formation of the diffraction grating will be described later.

  In the case of using the photolithography method, for example, an under cladding layer 124, a core layer 126, and a photoresist (not shown) are sequentially stacked on the substrate 91. Next, the photoresist is exposed and developed by a two-beam interference exposure method, and a diffraction grating (not shown) is formed on the main line portion 112 and the branch line portion 116. Next, for example, etching is performed by reactive ion etching (RIE) or the like to form the main line portion 112 and the branch line portion 116 in the core layer 126. Thereafter, for example, the over clad layer 122 is laminated.

  The formation of the diffraction grating will be described. In the wavelength selective reflection circuit 100 according to the first embodiment, the diffraction grating is preferably formed by a two-beam interference exposure method using ultraviolet rays. FIG. 3 shows a schematic diagram of a two-beam interference exposure apparatus used for forming a diffraction grating.

  The two-beam interference exposure apparatus 200 in FIG. 3 includes, for example, a He-Cd laser light source 210, four mirrors 220, a half mirror 230, a beam expander 240, two rotary stages 250, and an exposure window 260. FIG. 3 shows two gratings 132 out of many gratings appearing by the two-beam interference exposure method. The wavelength selective reflection circuit 100 is in a state before the overcladding layer is stacked. The He—Cd laser light source 210 preferably outputs ultraviolet light having a wavelength of 300 to 350 nm, and more preferably outputs ultraviolet light having a wavelength of 325 nm. The ultraviolet light output from the He-Cd laser light source 210 is expanded to a desired light diameter by the beam expander 240 via the two mirrors 220.

  The ultraviolet rays output from the beam expander 240 are divided into two by the half mirror 230, reflected by the two mirrors 220 arranged on the two rotary stages 250, and a large number of interference fringes on the wavelength selective reflection circuit 100. Form. The part where the grating 132 is formed is bright, the area between the gratings 132 is dark, and the refractive index of the part where the grating 132 is formed is low. Here, the two rotation stages 250 can be rotated by the same angle, and the interval between the gratings 132 can be freely controlled. In order to form the grating 132 at a desired location, the exposure window 260 is disposed in front of the selective reflection circuit 100. As shown in FIG. 1, when the intervals of the gratings 132 of the branch lines 116 are all different, as shown in FIG. 3, the selective reflection circuit 100 is moved along the movement direction A, and on the branch lines (not shown). The angle between the two gratings 132 may be adjusted by adjusting the angles of the desired two rotary stages 250. On the other hand, in the wavelength selective reflection circuit 100 according to the first embodiment, the intervals between the gratings 132 may be substantially equal. As described above, the wavelength selective reflection circuit 100 according to the first embodiment can easily form the wavelength selective reflection unit 130 having a desired reflection wavelength without using a phase grating mask. In addition, the wavelength selective reflection circuit 100 according to the first embodiment can have a larger wavelength tuning width per 1 ° C. than a quartz optical waveguide.

  The reflection wavelength of the diffraction grating formed by the two-beam interference exposure method will be described. FIG. 4 shows an enlarged view of the wavelength selective reflection circuit 100 of FIG. Further, FIG. 4 shows an interference angle θ that is an angle formed by the normal line X of the surface on which the grating 132 of the optical waveguide 110 is formed and the ultraviolet ray Y, and an interval Λ of the grating 132. Here, in the wavelength selective reflection circuit 100 according to the first embodiment, it is preferable that the interference angles θ of the two ultraviolet rays Y are substantially equal. The reflection wavelength of the diffraction grating can be easily calculated.

Here, the reflection wavelength of the diffraction grating can be expressed by, for example, Expression 1 and Expression 2. In Equations 1 and 2, λ _B is the reflection wavelength of the diffraction grating, n is the refractive index of the grating 132, Λ is the spacing of the grating 132, λ _UV is the wavelength of the ultraviolet light Y, and θ is the interference angle.
(Formula 1) λ _B = 2n × Λ
(Expression 2) Λ = λ _UV / (2 sin θ)

(Second Embodiment)
The multi-wavelength light source according to the second embodiment will be described mainly with respect to differences from the wavelength selective reflection circuit according to the first embodiment. FIG. 5 shows a top view of the multi-wavelength light source according to the second embodiment. The multi-wavelength light source 102 according to the second embodiment is a multi-wavelength light source 100 including a wavelength selective reflection circuit 100 and a semiconductor laser light source 140 coupled to the input / output end 114 of the main line portion 112 of the wavelength selective reflection circuit 100. Therefore, the reflection wavelength of the wavelength selective reflection unit 130 is included in the wavelength region where the semiconductor laser light source 140 can oscillate.

  The heater 120 is formed so that the main line portion 112 is sandwiched between the optical directional coupling circuit 118 and the heater 120 when the surface of the optical waveguide 110, for example, the wavelength selective reflection circuit 100 is viewed from above.

  The semiconductor laser light source 140 is, for example, an external resonance type semiconductor laser light source, and the oscillating wavelength region is 1500 to 1600 nm. The wavelength selective reflection unit 130 has a reflection wavelength of 1530 to 1570 nm, for example.

  In the main line portion 112 and the branch line portion 116, for example, a loss of an optical signal proportional to the optical path length from the input / output end 114 to the wavelength selective reflection portion 130 occurs due to transmission loss, backscattered light, or the like. When the optical path length from the input / output end 114 to the wavelength selective reflection unit 130 is different in each wavelength selective reflection unit 130, it is reflected by which wavelength selective reflection unit 130, that is, depending on the reflection wavelength of the wavelength selective reflection unit 130. A situation occurs in which the loss amount of the optical signal is different. Therefore, as shown in FIG. 5, in the multi-wavelength light source 102 according to the second embodiment, the wavelength selective reflection circuit 100 preferably has substantially the same optical path length from the input / output end 114 to the wavelength selective reflection unit 130. The multi-wavelength light source 102 can equalize the loss amount of the optical signal in proportion to the optical path length from the input / output end 114 to the wavelength selective reflection unit 130 in all the wavelength selective reflection units 130. As described above, the multi-wavelength light source 102 according to the second embodiment can easily form the wavelength selective reflection unit 130 having a desired reflection wavelength without using a phase grating mask. Further, the multi-wavelength light source 102 according to the second embodiment can take a larger wavelength tuning width per 1 ° C. than a quartz optical waveguide.

  FIGS. 6A and 6B are diagrams illustrating a coupling method of the semiconductor laser light source 140 and the wavelength selective reflection circuit 100, where FIG. 6A is a first coupling method, FIG. 6B is a second coupling method, and FIG. 6C is a third coupling method. It is a combination method. The first coupling method shown in FIG. 6A is a wavelength selection method in which a non-reflective coating film is formed on the output end (not shown) of the semiconductor laser 140, and the semiconductor laser 140 and the non-reflective coating are provided via the optical fiber 150. This is a method of coupling the reflection circuit 100. In the second coupling method shown in FIG. 6B, a non-reflective coating film is formed at the output end of the semiconductor laser 140 which is a semiconductor laser chip, and the semiconductor laser 140 is connected to the semiconductor laser 140 via a lens 160 having the non-reflective coating film formed thereon. In this method, the wavelength selective reflection circuit 100 coated with non-reflection is coupled. The third coupling method shown in FIG. 6C is a method of directly coupling the semiconductor laser light source 140 formed with the non-reflective coating film and the wavelength selective reflection circuit 100 coated with the non-reflective coating.

  The wavelength selective reflection circuit according to the present invention can be used as an optical signal reflection circuit. The multi-wavelength light source according to the present invention can be used as a light source for an optical network such as an optical WDM (Wavelength Division Multiplex).

It is a top view of the wavelength selective reflection circuit according to the first embodiment. FIG. 2 is a cross-sectional view taken along line A-A ′ of FIG. 1. It is the schematic of the two-beam interference exposure apparatus used for formation of a diffraction grating. FIG. 4 is an enlarged view of the wavelength selective reflection circuit of FIG. 3. It is a top view of the multiwavelength light source which concerns on 2nd Embodiment. It is a figure which shows the coupling | bonding method of a semiconductor laser light source and a wavelength selection reflection circuit.

Explanation of symbols

91 Substrate 100 Wavelength selective reflection circuit 102 Multi-wavelength light source 110 Optical waveguide 112 Main line portion 114 Input / output end 116 Branch line portion 118 Optical directional coupling circuit 120 Heater 130 Wavelength selective reflection portion 132 Grating 140 Semiconductor laser light source 150 Optical fiber 160 Lens 200 2 Beam interference exposure apparatus 210 He-Cd laser light source 220 Mirror 230 Half mirror 240 Beam expander 250 Rotating stage 260 Exposure window 270 Moving direction A Moving direction X Normal line Y Ultraviolet θ Interference angle Λ Distance between lattices

Claims (3)

An optical waveguide having an input / output end through which an optical signal is input and output is formed at one end and one or more branch lines coupled to the main line via an optical directional coupling circuit;
A wavelength selective reflection portion formed on the main line portion and the branch line portion, each having a different reflection wavelength, and
In the wavelength selective reflection circuit of polymer resin comprising
A wavelength formed by heating the optical directional coupling circuit to switch whether or not the optical signal is coupled to the branch line portion from the main line portion via the optical directional coupling circuit. Selective reflection circuit.   The wavelength selective reflection circuit according to claim 1, wherein the wavelength selective reflection unit is a diffraction grating having different refractive indexes and having gratings formed in the same direction. The wavelength selective reflection circuit according to claim 1 or 2,
A semiconductor laser light source coupled to the input / output end of the main line portion of the wavelength selective reflection circuit;
A multi-wavelength light source comprising:
The multi-wavelength light source, wherein the wavelength range in which the semiconductor laser light source can oscillate includes a reflection wavelength of the wavelength selective reflection portion.

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