Wavelength multiplexed light source

Abstract

A wavelength-multiplexing light source according to the present invention comprises a plurality of semiconductor lasers (11_1 to 11_N) and a single waveguide (12) that is near to the semiconductor lasers (11_1 to 11_N) with a low refractive index material (13_1) therebetween. Each of the plurality of semiconductor lasers (11_1 to 11_N) has a diffraction grating and oscillates at a different wavelength. Evanescent light is generated at the interfaces between the semiconductor lasers (11_1 to 11_N) and the low refractive index material (13_1), and the evanescent light is bound to the waveguide (12).　As a result, the present invention is capable of providing a compact wavelength-multiplexing light source that operates in a single mode.

Description

Technical Field

[0001] The present invention relates to a wavelength multiplexed light source using a coupled optical waveguide.

Background Art

[0002] In order to perform high-capacity information transmission by wavelength division multiplexing (WDM), various wavelength multiplexed light sources have been developed.

[0003] In a wavelength multiplexed light source, a laser array combines light from light sources having different oscillation wavelengths from different waveguides into an optical combiner. Non-Patent Document 1 discloses a wavelength multiplexed light source using four distributed feedback (DFB) lasers and a multimode interference (MMI) waveguide.

[0004] In addition, an integrated element of a light source and an arrayed waveguide grating combines light from light sources having different oscillation wavelengths with an arrayed waveguide grating (AWG). An AWG is a representative example of an optical combiner / splitter for WDM, and divides wavelengths using a multi-beam interference effect. For example, a wavelength multiplexed light source can be realized by integrating a small AWG (for example, Non-Patent Document 2) and a plurality (for example, four) of single-mode light sources (for example, Non-Patent Document 3).

[0005] Non-Patent Document 4 also discloses a wavelength multiplexed light source in which a plurality (for example, four) of disk-shaped resonator lasers are coupled in parallel to SOI (Silicon-on-insulator) thin wire waveguides.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

[0007] The size of the above laser array is 1000×1870 μm for four-wave multiplexing 2 (1.9 mm 2) This light source uses a waveguide with a large radius of curvature, and the bending waveguide and the multiplexer occupy a large area.

[0008] In the integrated element of the light source and the arrayed waveguide grating, when connecting the light source and the arrayed waveguide grating with a Si fine wire waveguide, its size is 340×1000 μm (0.3 mm 2 ) in 4-wave multiplexing, which is smaller than the laser array, but further miniaturization is required depending on the application.

[0009] In addition, the wavelength multiplexed light source disclosed in Non-Patent Document 4 can be miniaturized, but since it oscillates in multiple modes, it is difficult to apply it to wavelength multiplexed communication. For example, in Non-Patent Document 4, about 16.8 dB is reported as the side mode suppression ratio (SMSR), and it is difficult to apply it to wavelength multiplexed communication.

[0010] Thus, in order to apply to wavelength multiplexed communication, a small-sized and single-mode operating wavelength multiplexed light source is required.

Means for Solving the Problems

[0011] In order to solve the problems as described above, the wavelength multiplexed light source according to the present invention includes a plurality of semiconductor lasers, the semiconductor lasers, and a single waveguide adjacent via a low refractive index material. Each of the plurality of semiconductor lasers has a diffraction grating and oscillates at different wavelengths. Evanescent light is generated at the interface between the semiconductor laser and the low refractive index material, and the evanescent light is coupled to the waveguide and the plurality of semiconductor lasers are arranged in the waveguide direction and is characterized by this.

Effects of the Invention

[0012] According to the present invention, a small-sized and single-mode operating wavelength multiplexed light source can be provided.

Brief Description of the Drawings

[0013]

Figure 1

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Figure 5B

Figure 5C

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Figure 7A

Figure 7B

Figure 7C

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Figure 9A

Figure 9B

Figure 9C

Figure 10

Embodiments for Carrying Out the Invention

[0014] <First Embodiment> A wavelength multiplexed light source according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4.

[0015] <Configuration of Wavelength Multiplexed Light Source> As shown in FIG. 1, the wavelength multiplexed light source according to the present embodiment includes a plurality of semiconductor lasers 11_1 to 11_N, a semiconductor bus waveguide 12, and a low refractive index material 13_1. The plurality of semiconductor lasers 11_1 to 11_N are close to a single waveguide 12 via the low refractive index material 13_1. Further, the plurality of semiconductor lasers 11_1 to 11_N each have a diffraction grating with a different period, oscillate at different wavelengths, and are arranged in the waveguide direction (Y direction in the figure).

[0016] The laser light of the semiconductor lasers 11_1 to 11_N is evanescently coupled to the surrounding low refractive index material to emit evanescent light. Among this evanescent light, the evanescent light emitted toward the semiconductor bus waveguide 12 is coupled to the semiconductor bus waveguide 12 and propagates through the semiconductor bus waveguide 12 as shown in FIG. 2 (solid line arrow in the figure). Further, it is also conceivable that the light propagating through the semiconductor bus waveguide 12 is incident on the semiconductor lasers 11_1 to 11_N (dotted line arrow in the figure).

[0017] Here, the semiconductor lasers 11_1 to 11_N and the semiconductor bus waveguide 12 are separated by a distance of about several microns or less, and the evanescent coupling strength can be changed by this distance and the structure of the semiconductor bus waveguide 12.

[0018] Since the plurality of semiconductor lasers 11_1 to 11_N each oscillate laser light at a different wavelength, multi-wavelength laser light propagates through the semiconductor bus waveguide 12 and is emitted from an emission end face (not shown). Alternatively, it may be coupled to other optical elements.

[0019] Next, the coupling between the light propagating in the semiconductor bus waveguide and the semiconductor laser was calculated. The coupled-wave theory was used for the calculation (J.-P. Weber, “Spectral characteristics of coupled-waveguide Bragg-reflection tunable optical filter,” IEEE Proceedings Journal, Vol. 140, No. 5, pp. 275-284 (1993). Wei Shi et al., “Silicon photonic grating-assisted, contra-directional couplers,” Optics Express, Vol. 21, No. 3, pp. 181375 (2013).).

[0020] Also, in the structure in which the waveguide is coupled to the diffraction grating shown in FIG. 3, for the incident light I incident from one end of one waveguide, the transmitted light T emitted from the other end of one waveguide and the reflected light R emitted from one end of the other waveguide were calculated. In the calculation, the refractive indices of the materials were 2.61 and 2.45, and the coupling coefficient was 183 cm -1 was used.

[0021] FIG. 4 shows the spectrum of the reflected light (solid line in the figure) and the spectrum of the transmitted light (dotted line in the figure) with respect to the incident light I.

[0022] As shown in FIG. 4, the reflected light spectrum has a resonance peak at a wavelength of about 1518 nm. On the other hand, the transmitted light spectrum also has a resonance peak at a wavelength of about 1518 nm. Also, in the transmitted light spectrum, the transmittance is about 1.0 in the wavelength region less than 1510 nm and longer than 1525 nm.

[0023] This indicates that if there is a predetermined wavelength difference between the wavelength of the incident light and the resonance wavelength of the diffraction grating of the semiconductor laser, the incident light will transmit without being reflected by the diffraction grating. For example, in the structure used in the above calculation, the predetermined wavelength difference may be 15 nm or more.

[0024] Therefore, in this embodiment, even if the laser light propagating in the semiconductor bus waveguide enters another semiconductor laser, it passes through without being reflected by the diffraction grating of the other semiconductor laser, so it does not interfere with the laser light of the other semiconductor laser and does not affect the oscillation of the other semiconductor laser, such as making it unstable.

[0025] In other words, a predetermined wavelength difference is set between the wavelength of the incident light and the resonance wavelength of the diffraction grating of the semiconductor laser. That is, if the period of the diffraction grating of one semiconductor laser among the plurality of semiconductor lasers is set so as to transmit the oscillation light of the other semiconductor laser, it is possible to avoid the oscillation light of the other semiconductor laser from affecting the operation of one semiconductor laser.

[0026] <First Embodiment> The wavelength multiplexed light source according to the first embodiment of the present invention will be described with reference to FIGS. 5A to 7B.

[0027] <Configuration of Wavelength Multiplexed Light Source> As shown in FIGS. 5A to 5C, the wavelength multiplexed light source 20 according to this embodiment includes a plurality (for example, three) of DFB lasers 21_1 to 21_3 and a semiconductor bus waveguide 22.

[0028] As shown in FIG. 5A, in the wavelength multiplexed light source 20, a plurality of DFB lasers 21_1 to 21_3 are arranged in the waveguide direction (in the Y direction in the figure), and an insertion layer 23 is arranged between each of the plurality of DFB lasers 21_1 to 21_3. The insertion layer 23 is made of SiO2 and may be a dielectric such as SiN, as long as it has a refractive index lower than that of the material (for example, InP-based semiconductor) constituting the DFB laser.

[0029] The lengths of the DFB lasers 21_1 to 21_3 are 100 μm, and the interval between each of the DFB lasers 21_1 to 21_3 in the waveguide direction, that is, the length of the insertion layer 23 in the waveguide direction, is 200 μm.

[0030] As shown in Fig. 5B, the wavelength multiplexed light source 20 includes, in order, an SiO2 layer 202, a semiconductor bus waveguide 22, a coupling layer 24, and DFB lasers 21_1 to 21_3 on an Si substrate 201. In this way, the semiconductor bus waveguide 22 is disposed close to the DFB lasers 21_1 to 21_3.

[0031] The semiconductor bus waveguide 22 may be made of Si or any material that can propagate the laser light of the DFB lasers 21_1 to 21_3. Its width is 3 μm and its thickness is 100 nm.

[0032] The coupling layer 24 may be made of SiO2 or a dielectric such as SiN, as long as it has a refractive index lower than that of the material constituting the DFB laser (for example, an InP-based semiconductor). Its thickness, that is, the distance between the semiconductor bus waveguide 22 and the DFB lasers 21_1 to 21_3, is 250 nm. This distance may be in the range of 100 nm to 500 nm, as long as the evanescent light can be coupled to the semiconductor bus waveguide 22.

[0033] As shown in Figs. 5A and 5C, the DFB lasers 21_1 to 21_3 are formed by laminating a first semiconductor layer (InP) 211, a multi quantum well (MQW) 212 as an active layer, and a second semiconductor layer (InP) 213. The width of this laminated structure, that is, the width of the active layer, is about 1.0 μm. On one side surface in the width direction (X direction in the figure) of the active layer 212, a p-type semiconductor (InP) layer 215_1 is disposed in contact, and a p-type electrode (for example, gold) 216_1 is provided thereon via a p-type contact layer (for example, p-type InGaAs, not shown). On the other side surface, an n-type semiconductor (InP) layer 215_2 is disposed in contact, and an n-type electrode (for example, gold) 216_2 is provided thereon via an n-type contact layer (for example, n-type InGaAs, not shown).

[0034] Here, for example, the MQW active layer 212 is composed of an InGaAsP well layer and an InGaAsP barrier layer in the 1.55 μm wavelength band, and has a thickness of about 105 nm for 6 periods. The thicknesses of the first semiconductor layer (InP) 211 and the second semiconductor layer (InP) 213 are 165 nm and 80 nm, respectively. Also, the thicknesses of the p-type semiconductor (InP) layer 215_1 and the n-type semiconductor (InP) layer 215_2 are 350 nm.

[0035] Here, the MQW active layer 212 may be in the 1.31 μm wavelength band. For the MQW, InGaAs, GaInNAs, etc. may be used instead of InGaAsP. The configuration such as the period and thickness of the MQW may be other configurations.

[0036] In the DFB lasers 21_1 to 21_3, a DFB diffraction grating 214 is provided on the upper surface of the second semiconductor layer (InP) 213 above the active layer 212. The coupling coefficient of the DFB diffraction grating 214 is determined by the refractive index of InP and the refractive index of air. Here, in the DFB diffraction grating 214, for example, the pitch (period) is about 200 nm to 300 nm, the depth is about 10 nm to 50 nm, and is set according to the desired emission (oscillation) wavelength and coupling coefficient.

[0037] Also, a diffraction grating may be provided at the boundary between the active layer 212 and the first semiconductor layer (InP) below it.

[0038] Thus, the DFB lasers 21_1 to 21_3 have a membrane-type laser configuration, current is injected laterally (width direction) into the active layer 212, laser oscillation occurs, and laser light is emitted (in the figure, arrow 15).

[0039] The plurality of DFB lasers 21_1 to 21_3 each oscillate laser light at different wavelengths, for example, 1505 nm, 1520 nm, and 1535 nm.

[0040] The laser light of the DFB lasers 21_1 to 21_3 is evanescently coupled to the coupling layer to emit evanescent light. This evanescent light is coupled to the semiconductor bus waveguide 22 and propagates through the semiconductor bus waveguide 22.

[0041] Since the plurality of DFB lasers 21_1 to 21_3 each oscillate laser light at different wavelengths, multi-wavelength laser light propagates through the semiconductor bus waveguide 22 and is emitted from an emission end face (not shown). Alternatively, it may be coupled to other optical elements.

[0042] <Method for manufacturing a wavelength multiplexed light source> A method for manufacturing the wavelength multiplexed light source 20 according to this embodiment will be described with reference to FIG. 6. FIG. 6 shows a VC-VC' cross-sectional view of the wavelength multiplexed light source 20.

[0043] First, using an SOI substrate composed of an Si substrate 201, an SiO2 layer 202, and an Si layer 22_1 (S1_1), the Si layer 22_1 of the SOI substrate is processed by lithography, dry etching, etc. to form the semiconductor bus waveguide 22 (S1_2).

[0044] Next, SiO2 24 is formed by a method such as chemical vapor deposition (CVD), and its surface is planarized by a method such as chemical mechanical polishing (CMP) (S1_3).

[0045] Next, a wafer including the active layer crystal 212_1 is bonded by a method such as wafer bonding, and the support substrate is removed, so that the semiconductor thin films 211 and 212_1 including the active layer crystal are formed on the SiO2 24 of the SOI substrate processed in step (S1_3) (S1_4).

[0046] Next, the semiconductor thin films 211 and 212_1 including the active layer crystal are processed by etching to form the active layer (waveguide structure) 212 (S1_5). Thereby, the laser structure and the semiconductor bus waveguide 22 can be arranged in parallel in the vertical direction (Z direction in the figure).

[0047] Next, the active layer is embedded with InP by crystal regrowth. Next, p-type InP215_1 is formed on one side surface, and n-type InP215_2 is formed on the other side surface (S1_6). For example, p-type InP215_1 is formed by Zn diffusion, and the n-type InP layer 215_2 is formed by ion implantation. As a result, an undoped InP layer 213 is formed on the active layer 212.

[0048] Next, a diffraction grating 214 is formed on the surface (upper surface) of the InP layer 213 on the active layer (S1_7).

[0049] Finally, electrodes 216_1 and 216_2 are formed on p-type InP215_1 and n-type InP215_2, respectively (S1_8).

[0050] In the wavelength multiplexed light source 20, since the optical coupling strength between the DFB lasers 21_1 to 21_3 and the semiconductor bus waveguide 22 strongly depends on the distance between the DFB lasers 21_1 to 21_3 and the semiconductor bus waveguide 22, control of this distance is important. In the wavelength multiplexed light source 20, since the distance between the DFB lasers 21_1 to 21_3 and the semiconductor bus waveguide 22 corresponds to the thickness of the coupling layer 24, control of this distance depends on the film formation accuracy and the CMP accuracy.

[0051] On the other hand, when the DFB lasers 21_1 to 21_3 and the semiconductor bus waveguide 22 are arranged horizontally, the manufacturing error of the distance between the DFB lasers 21_1 to 21_3 and the semiconductor bus waveguide 22 depends on the lithography etching accuracy.

[0052] Therefore, since the film formation accuracy is usually higher than the lithography etching accuracy, according to the manufacturing method according to the present embodiment, the optical coupling between the DFB laser and the semiconductor bus waveguide can be controlled with high precision.

[0053] <Effect> When assuming an integrated element (Non-Patent Documents 2 and 3) of a light source and an arrayed waveguide grating as a conventional wavelength multiplexed light source, as described above, its size is 340×1000 μm (0.3 mm 2 )

[0054] On the other hand, assuming that a laser of the same size as the light source (laser) of a conventional wavelength-division multiplexed light source is used, the size of the wavelength-division multiplexed light source according to the present embodiment is 60×1150 μm (0.07 mm2), and can be reduced to about 1 / 5 compared to a conventional wavelength-division multiplexed light source.

[0055] Furthermore, in the wavelength-division multiplexed light source according to the present embodiment, since the semiconductor laser resonates with the diffraction grating, its oscillation wavelength can be easily controlled by changing the period of the diffraction grating, and good single-mode characteristics can be realized with an SMSR of 40 dB or more.

[0056] Thus, according to the wavelength-division multiplexed light source according to the present embodiment, a wavelength-division multiplexed light source that is small and operates in single mode can be realized.

[0057] In the present embodiment, an example in which a DFB laser is used for the semiconductor laser is shown, but the present invention is not limited thereto. As shown in FIGS. 7A to 7C, a distributed Bragg reflector (DBR) laser may be used. When a DBR laser is used, spatial hole burning can be suppressed and the mode stability can be improved compared to a DFB laser.

[0058] <Second Embodiment> The wavelength-division multiplexed light source according to the second embodiment of the present invention will be described with reference to FIG. 8.

[0059] <Configuration of Wavelength-Division Multiplexed Light Source> As shown in FIG. 8, the wavelength-division multiplexed light source 40 according to the present embodiment includes a plurality of semiconductor lasers 41_1 to 41_4 and a semiconductor bus waveguide 42. The plurality of semiconductor lasers 41_1 to 41_4 have different oscillation wavelengths and are arranged in the width direction (X direction in the figure).

[0060] Further, the semiconductor bus waveguide 42 is linearly arranged in the waveguide direction (Y direction in the figure) in a region close to the semiconductor lasers 41_1 to 41_4, but is arranged in a curved shape in the region between the respective semiconductor lasers 41_1 to 41_4. In this way, the semiconductor bus waveguide 42 has an S shape as a whole. Other configurations are the same as those in the first embodiment.

[0061] According to the wavelength multiplexed light source according to the present embodiment, since the wire wiring can be shortened, good high-frequency characteristics can be realized.

[0062] Further, in the present embodiment, by using a Si fine wire waveguide with a small bending radius, this configuration can be realized without increasing the element size.

[0063] Further, in the wavelength multiplexed light source according to the present embodiment, by adopting a configuration in which a diffraction grating is not provided in the semiconductor laser structure (for example, 41_4) on the side opposite to the emission end, this semiconductor laser structure can be used as a simple type light receiver to monitor the output light intensity from the wavelength multiplexed light source.

[0064] <Third Embodiment> The wavelength multiplexed light source according to the third embodiment of the present invention will be described with reference to FIG. 9.

[0065] <Configuration of Wavelength Multiplexed Light Source> The wavelength multiplexed light source according to the present embodiment includes a plurality of DFB lasers 51_1 to 51_3 and a semiconductor bus waveguide 52, as shown in FIGS. 9A to 9C.

[0066] As shown in FIG. 9A, in the wavelength multiplexed light source, a plurality of DFB lasers 51_1 to 51_3 are arranged in the waveguide direction (Y direction in the figure), and an insertion layer 53 is arranged between each of the plurality of DFB lasers 51_1 to 51_3.

[0067] The DFB lasers 51_1 to 51_3 include, in order, an InP layer 511, an active layer 512 composed of MQW, an InP layer 513, and a p-type InP clad 515_1 on an n-type InP substrate 501. Further, an n-type electrode 516_2 is provided on the back surface of the n-type InP substrate, and an n-type electrode 516_1 is provided on the surface of the p-type InP clad.

[0068] The semiconductor bus waveguide 52 is disposed close to the side walls of the DFB lasers 51_1 to 51_3 in the width direction (the X direction in the figure). Further, the semiconductor bus waveguide 52 is formed on SiO2 502 provided on the n-type InP substrate 501, and the side walls and the upper surface are covered with a SiO2 clad (insertion layer) 53.

[0069] Here, the side walls of the DFB lasers 51_1 to 51_3 and the side walls of the semiconductor bus waveguide 52 are brought close to each other via a semi-insulating InP embedding layer 517 and a SiO2 clad (insertion layer) 53 in the width direction. The sum of the widths of the semi-insulating InP embedding layer 517 and the SiO2 clad (insertion layer) 53, that is, the distance between the side walls of the DFB lasers 51_1 to 51_3 and the side walls of the semiconductor bus waveguide 52 may be 100 nm to 500 nm.

[0070] Further, the width of the semiconductor bus waveguide 52 is 3 μm and the thickness is 100 nm.

[0071] Other configurations are substantially the same as those in the first embodiment.

[0072] <Method for manufacturing a wavelength multiplexed light source> The method for manufacturing a wavelength multiplexed light source according to this embodiment will be described with reference to FIG. 10. FIG. 10 shows a VIVC-VIVC' cross-sectional view of the wavelength multiplexed light source.

[0073] First, using an n-type InP substrate 501 (S3_1), an InP layer 511_1, an active layer 512_1, and an InP layer 513_1 are sequentially grown on the n-type InP substrate 501 (S3_2).

[0074] Next, a diffraction grating 514 is formed on the upper light confinement InP layer (S3_3).

[0075] Next, p-type InP 515_1 is crystal-grown on the InP layer 513_1 on which the diffraction grating 514 is formed (S3_4).

[0076] Next, the crystal-grown laminated structure is etched to form a mesa structure (S3_5).

[0077] Next, the side regions of the mesa structure are filled with semi-insulating (S.I.) InP 517 by crystal regrowth (S3_6).

[0078] Next, a part of the semi-insulating InP layer 517 and the n-type InP substrate 501 on one side of the side region of the mesa structure are removed by etching (S3_7). At this time, etching is performed so that the semi-insulating InP layer 517 remains with a thickness (width) of about 100 to 500 nm on one side wall of the mesa structure.

[0079] Next, SiO2 502 is deposited on the region removed from the n-type InP substrate 501 (S3_8).

[0080] Next, after amorphous Si is deposited on the deposited SiO2 502, etching is performed to form an amorphous Si waveguide 52 (S3_9). Here, the material of the waveguide 52 is not limited to amorphous Si, and any high refractive index material may be used.

[0081] Next, SiO2 53 is deposited so as to cover the amorphous Si waveguide 52 (S3_10).

[0082] Finally, an n-type electrode 516_2 is formed on the back surface of the n-type InP substrate 501, and a p-type electrode 516_1 is formed on the surface of the p-type InP 515. At this time, the n-type electrode 516_2 and the p-type electrode 516_1 may be formed on the back surface of the n-type InP substrate 501 and the surface of the p-type InP 515, respectively, via an ohmic contact layer.

[0083] The configuration of the buried DFB laser used in this embodiment has already been proven reliable. Therefore, according to the wavelength multiplexed light source according to this embodiment, the reliability can be improved.

[0084] In the embodiment of the present invention, an example of the configuration of a semiconductor laser in the 1.55 μm wavelength band is shown, but other wavelength bands such as 1.31 μm may also be used. Further, as an example of the layer configuration of a semiconductor laser such as an active layer, a waveguide layer, p-type and n-type semiconductor layers, a configuration using an InP-based compound semiconductor is shown, but other InP-based compound semiconductors may be used, or other semiconductors such as GaAs-based and Si-based semiconductors may be used, and any material that can form a semiconductor laser may be used.

[0085] In the embodiment of the present invention, in the configuration, manufacturing method, etc. of a wavelength multiplex light source, examples of the structure, dimensions, materials, etc. of each component are shown, but it is not limited thereto. Any configuration that can exhibit the function of the wavelength multiplex light source and achieve the effects may be used.

Industrial Applicability

[0086] The present invention relates to a wavelength multiplex light source and can be applied to a wavelength division multiplexing (WDM) communication system or the like.

Explanation of Reference Numerals

[0087] 10 Wavelength multiplex light source 11_1~11_N Semiconductor lasers 12 Semiconductor bus waveguide 13_1, 13_2 Low refractive index materials

Claims

1. A plurality of semiconductor lasers, a single waveguide that is adjacent to the semiconductor laser via a low refractive index material, and each of the plurality of semiconductor lasers has a diffraction grating and oscillates at a different wavelength, evanescent light is generated at the interface between the semiconductor laser and the low refractive index material, the evanescent light is coupled to the waveguide, and the plurality of semiconductor lasers are arranged in the waveguide direction A wavelength multiplexed light source characterized by this.

2. The period of the diffraction grating of one of the plurality of semiconductor lasers is set so as to transmit the oscillation light of the other semiconductor lasers. The wavelength multiplexed light source according to claim 1, characterized by this.

3. The distance between the semiconductor laser and the waveguide is 100 nm or more and 500 nm or less. The wavelength multiplexed light source according to claim 1 or claim 2, characterized by this.

4. In order, a substrate, the waveguide, the low refractive index material, and the semiconductor laser and the semiconductor laser has a waveguide structure including a first semiconductor layer, an active layer, and a second semiconductor layer in this order from the low refractive index material, a p-type semiconductor layer disposed in contact with one side surface of the active layer, an n-type semiconductor layer disposed in contact with the other side surface of the active layer, and the diffraction grating is disposed on either the upper surface of the second semiconductor layer or the lower surface of the first semiconductor layer. The wavelength multiplexed light source according to any one of claims 1 to 3, characterized by this.

5. A waveguide structure including, in order, a substrate, a first semiconductor layer, an active layer, a second semiconductor layer, and a cladding layer, A semi-insulating semiconductor layer disposed in contact with both side surfaces of the active layer, The waveguide disposed close to one of the side surfaces of the active layer and comprising The wavelength multiplex light source according to any one of claims 1 to 3, characterized in that.

6. The waveguide is Si The wavelength multiplex light source according to any one of claims 1 to 5, characterized in that.

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