Wavelength variable light source

Abstract

To shorten the time required for mounting.SOLUTION: A wavelength variable light source includes: a first substrate on which a gain chip including a first optical waveguide and an optical amplifier including a second optical waveguide are formed; and a second substrate on which a wavelength variable block including a wavelength variable element, a third optical waveguide to be connected to an input end of the wavelength variable block, and a fourth optical waveguide to be connected to an output end of the wavelength variable block are formed. In the wavelength variable light source, the first optical waveguide and the third optical waveguide are optically coupled to each other, and the second optical waveguide and the fourth optical waveguide are optically coupled to each other by mounting the first substrate on the second substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to tunable light sources. [Background technology]

[0002] As a related technique, Patent Document 1 discloses a multi-wavelength light source. The multi-wavelength light source described in Patent Document 1 includes a laser, an optical amplifier, an optical splitter, and an output waveguide. The laser includes a laser gain medium and multiple diffraction gratings. The optical amplifier collectively amplifies multiple wavelength laser light output from the laser. The optical splitter splits the output light from the optical amplifier. The output waveguide is connected to the optical splitter and outputs light of multiple wavelengths.

[0003] In Patent Document 1, a laser gain medium and an optical amplifier are formed on the same substrate and are separated from each other by a dividing groove. A plurality of diffraction gratings, an optical demultiplexer, and an output waveguide are formed on a silicon photonics substrate. A groove or a recess is formed in the silicon photonics substrate. The substrate on which the laser gain medium and the optical amplifier are formed is accommodated in the groove or recess formed in the silicon photonics substrate and mounted on the silicon photonics substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-197837 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, tunable light sources having a light source and a wavelength-selective filter have been configured to optically couple a silicon photonics (SiP) element equipped with a wavelength-selective filter to a gain chip, which serves as the light source. Furthermore, to provide the tunable light source with the ability to adjust its optical output, a semiconductor optical amplifier (SOA) is often coupled to the end face of the SiP element. In such tunable light sources, the light output from the gain chip is input to the wavelength-selective filter, and the light output from the wavelength-selective filter is input to the SOA.

[0006] The light source described in Patent Document 1 is a multi-wavelength light source, and light output from a laser is input directly to an optical amplifier on the same substrate. In Patent Document 1, the gain chip cannot selectively input light of a desired wavelength to the optical amplifier, and the optical amplifier amplifies multiple wavelength laser light collectively. Generally, in a wavelength-tunable light source, the gain chip and the semiconductor optical amplifier are formed on separate substrates and individually connected to the wavelength tuning block. In this case, the substrate on which the gain chip is formed and the substrate on which the semiconductor optical amplifier is formed must be individually mounted on a silicon photonics substrate. This poses the problem of time-consuming mounting and low productivity.

[0007] An exemplary object of the present disclosure is to provide a tunable light source that can reduce the time required for implementation. [Means for solving the problem]

[0008] A tunable light source according to one aspect of the present disclosure includes a first substrate on which a gain chip including a first light guide and an optical amplifier including a second light guide are formed, a tunable block including a wavelength tunable element, a third light guide connected to an input end of the tunable block, and a fourth light guide connected to an output end of the tunable block. By mounting the tunable light source on the first substrate and the second substrate, the first light guide and the third light guide are optically coupled, and the second light guide and the fourth light guide are optically coupled. [Effects of the Invention]

[0009] The tunable light source according to the present disclosure can reduce the time required for implementation. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a layout diagram showing a configuration example of a first wavelength-tunable light source according to the present disclosure. [Figure 2] FIG. 10 is a layout diagram showing a configuration example of a second wavelength-tunable light source according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the following description and drawings have been omitted and simplified as appropriate for clarity of explanation. In addition, in the following drawings, the same or similar elements are designated by the same reference numerals, and duplicate explanations are omitted as necessary.

[0012] A first embodiment will be described. FIG. 1 is a layout diagram showing a configuration example of a first wavelength-tunable light source according to the present disclosure. The wavelength-tunable light source 100 shown in FIG. 1 has a first substrate 120 and a second substrate 130. In the wavelength-tunable light source 100, the first substrate 120 is mounted on the second substrate 130. In the following description, the side surface of the first substrate 120 adjacent to the second substrate 130 will be referred to as a first end face. Also, the side surface of the second substrate 130 adjacent to the first substrate 120 will be referred to as a second end face.

[0013] The first substrate 120 has a gain chip 121, which is a light source, and an optical amplifier 122. The first substrate is also called an optical semiconductor substrate. The gain chip 121 is an element used as an optical gain medium of an external cavity laser. The gain chip 121 includes a first optical guide 125. The optical amplifier 122 is a semiconductor optical amplifier, which is a device that amplifies laser light. The optical amplifier 122 includes a second optical guide 126. The optical amplifier 122 is used to adjust the optical output of the wavelength-tunable light source 100. In the first substrate 120, the first optical guide 125 and the second optical guide 126 are each formed from a first end face to an end face opposite the first end face.

[0014] The second substrate 130 is, for example, a silicon-on-insulator (SOI) substrate, which is a silicon photonics substrate in which optical waveguides and optical elements are formed using silicon wire waveguides. The second substrate 130 is also called an optical integrated circuit or optical integrated element. The second substrate 130 has a wavelength tuning block 131, a third light guide path 135, and a fourth light guide path 136. The wavelength tuning block 131 includes a wavelength selection filter or wavelength selection element such as a diffraction grating. The third light guide path 135 is formed from a second end face of the second substrate 130 to an input end of the wavelength tuning block 131. The fourth light guide path 136 is formed from the second end face of the second substrate 130 to an output end of the wavelength tuning block 131.

[0015] The first light guide path 125 and the second light guide path 126 each extend to a first end face of the first substrate 120. The third light guide path 135 and the fourth light guide path 136 each extend to a second end face of the second substrate 130. The first light guide path 125 and the second light guide path 126 are exposed at the first end face, and the third light guide path 135 and the fourth light guide path 136 are exposed at the second end face. In mounting, the first substrate 120 is mounted on the second substrate 130 so that the first end face and the second end face are bonded. In this manner, the first light guide path 125 and the second light guide path 126 of the first substrate 120 are optically coupled to the third light guide path 135 and the fourth light guide path 136 of the second substrate 130.

[0016] The height, position, and size of the first end face of the first light guide 125 are the same as the height, position, and size of the second end face of the third light guide 135. The height, position, and size of the first end face of the second light guide 126 are the same as the height, position, and size of the second end face of the fourth light guide 136. When the first substrate 120 is mounted on the second substrate 130, the first light guide 125 on the first substrate 120 is optically coupled to the third light guide 135 on the second substrate 130 by end-face coupling. The second light guide 126 on the first substrate 120 is optically coupled to the fourth light guide 136 on the second substrate 130 by end-face coupling.

[0017] In the gain chip 121, a reflective coating is applied to the end face opposite to the first end face of the first light guide 125. Light output from the gain chip 121 is input from the first light guide 125 to the third light guide 135 and input to the wavelength tunable block 131 through the third light guide 135. Light output from the wavelength tunable block 131, i.e., laser light, is input from the fourth light guide 136 to the second light guide 126 and amplified in the optical amplifier 122. The wavelength tunable light source 100 outputs the amplified laser light from the end face opposite to the first end face of the second light guide 126. The amplification factor of the optical amplifier 122 is adjusted so as to obtain a desired optical output.

[0018] In this embodiment, light output from the gain chip 121 is input to the wavelength tunable block 131, and light output from the wavelength tunable block 131 is input to the optical amplifier 122. In implementation, the first light guide 125 and the second light guide 126 formed on the first substrate 120 are optically coupled to the third light guide 135 and the fourth light guide 136, respectively. In this manner, the gain chip 121 formed on the first substrate 120 and the optical amplifier 122 are connected via the wavelength tunable block 131 formed on the second substrate 130. In this embodiment, the optical amplifier 122 amplifies light of a wavelength selected in the wavelength tunable block 131.

[0019] Now, consider a case where the gain chip 121 and the optical amplifier 122 are formed on separate substrates. In that case, two optical semiconductor substrates need to be individually mounted on the second substrate 130, which is a silicon photonics substrate. In other words, elements need to be mounted twice on the silicon photonics substrate. This requires time for mounting. In this embodiment, the gain chip 121 and the optical amplifier 122 are formed on the same substrate, so a wavelength-tunable light source with adjustable optical output can be obtained by mounting only once. Therefore, compared to a case where the gain chip 121 and the optical amplifier 122 are formed on separate substrates, the time required for mounting can be shortened, and productivity can be improved.

[0020] In this embodiment, by joining the first end face of the first substrate 120 and the second end face of the second substrate 130, the first light guide path 125 and the second light guide path 126 are optically coupled to the third light guide path 135 and the fourth light guide path 136. In this embodiment, the first substrate 120 is mounted on the second substrate 130 at one side surface, which makes mounting easier than when the first substrate 120 is mounted on the second substrate 130 at two or more side surfaces.

[0021] Next, a second embodiment will be described. Fig. 2 is a layout diagram showing a configuration example of a second wavelength-tunable light source according to the present disclosure. In the wavelength-tunable light source 100a shown in Fig. 2, the first substrate 120a has a light source 141, a fifth light guide 142, a sixth light guide 143, and a photodetector (Photo Detector (PD)) 144 in addition to the configuration of the first substrate 120 in the wavelength-tunable light source 100 shown in Fig. 1. Furthermore, the second substrate 130a has a seventh light guide 137 in addition to the configuration of the second substrate 130 in the wavelength-tunable light source 100 shown in Fig. 1.

[0022] The light source 141 outputs laser light of a predetermined wavelength. The light source 141 may be a semiconductor laser such as a distributed feedback laser diode (DFB) laser or a Fabry-Perot (FP) laser. The photodetector 144 detects the input light. The photodetector 144 includes, for example, an SOA, and the SOA is used as the photodetector. The light source 141 and the photodetector 144 are formed in an area of ​​the first substrate 120a outside the area in which the gain chip 121 and the optical amplifier 122 are formed. The fifth light guide 142 is connected to the light source 141. The sixth light guide 143 is connected to the photodetector 144. The fifth light guide 142 and the sixth light guide 143 each extend to a first end face of the first substrate 120a and are exposed at the first end face.

[0023] The seventh light guide 137 extends from one position on the second end surface of the second substrate 130a to another position on the second end surface. When the first substrate 120a is mounted on the second substrate 130a, one end of the seventh light guide 137 is connected to the fifth light guide 142 and the other end is connected to the sixth light guide 143. The seventh light guide 137 is formed in a region on the second substrate 130a outside the wavelength tunable block 131. The seventh light guide 137 is formed, for example, along the outer edge of the second substrate 130a as shown in FIG. 2.

[0024] The light source 141 is turned on when the first substrate 120a is mounted on the second substrate 130a. When the first substrate 120a is mounted on the second substrate 130a, the fifth light guide 142 connected to the light source 141 is optically coupled by end-face coupling to one end of the seventh light guide 137 formed on the second substrate 130a. Furthermore, the sixth light guide 143 connected to the photodetector 144 is optically coupled by end-face coupling to the other end of the seventh light guide 137 formed on the second substrate 130a.

[0025] Light output from the light source 141 is input from a fifth light guide path 142 to a seventh light guide path 137 formed on the second substrate 130a at the boundary between the first substrate 120a and the second substrate 130a. The light input to the seventh light guide path 137 is input to a sixth light guide path 143 to which a photodetector 144 is connected. The photodetector 144 detects the light input from the sixth light guide path 143. During mounting, the relative positional relationship between the first substrate 120a and the second substrate 130a is adjusted while monitoring the amount of light detected by the photodetector 144. The mounting position is adjusted, for example, so that the current flowing through a semiconductor optical amplifier used as the photodetector 144 is maximized. In other words, the mounting position of the first substrate 120a is adjusted so that the amount of light received by the photodetector 144 is maximized.

[0026] Generally, when mounting a gain chip on a SiP substrate, it is necessary to control the characteristics of the optical elements on the SiP substrate to ensure accurate alignment. For example, during mounting, the mounting position is adjusted while monitoring the optical output wavelength or intensity of the wavelength tunable block, and the gain chip is mounted on the SiP substrate at a position that provides optimal characteristics. In this case, controlling the optical characteristics of the SiP element takes time, which reduces productivity.

[0027] In contrast, in this embodiment, mounting can be performed based on the amount of light received by the photodetector 144 formed on the first substrate 120a. For example, the first substrate 120a is mounted on the second substrate 130a so as to maximize the amount of light received by the photodetector 144. In this embodiment, control of the elements on the second substrate 130a is not required during mounting. Therefore, in this embodiment, the first substrate 120a can be mounted on the second substrate 130a without reducing productivity.

[0028] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0029] Each drawing is merely an example for describing one or more embodiments. Each drawing may relate not only to one particular embodiment, but also to one or more other embodiments. As will be understood by those skilled in the art, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings to create, for example, an embodiment not explicitly shown or described. Not all features or steps shown in any one drawing are necessary to describe an exemplary embodiment, and some features or steps may be omitted. The order of steps described in any drawing may be changed as appropriate.

[0030] A part or all of the above-described embodiments can be described as, but not limited to, the following supplementary notes.

[0031] [Appendix 1] A wavelength tunable light source, a first substrate on which a gain chip including a first optical waveguide and an optical amplifier including a second optical waveguide are formed; a wavelength tunable block including a wavelength tunable element, and a second substrate on which a third light guide path connected to an input end of the wavelength tunable block and a fourth light guide path connected to an output end of the wavelength tunable block are formed; a tunable light source, wherein the first light guide path and the third light guide path are optically coupled, and the second light guide path and the fourth light guide path are optically coupled, by being mounted on the first substrate and the second substrate.

[0032] [Appendix 2] the first light guide path and the second light guide path each extend to a first end face of the first substrate, and the third light guide path and the fourth light guide path each extend to a second end face of the second substrate; 2. The tunable light source according to claim 1, wherein the first substrate is mounted on the second substrate by bonding the first end face and the second end face together.

[0033] [Appendix 3] 3. The tunable light source according to claim 1, wherein the first light guide path and the second light guide path are optically coupled to the third light guide path and the fourth light guide path by end face coupling.

[0034] [Appendix 4] 4. The tunable light source according to any one of claims 1 to 3, wherein the first substrate is an optical semiconductor substrate and the second substrate is a silicon photonics substrate.

[0035] [Appendix 5] the first substrate further includes a light source, a fifth light guide connected to the light source, a photodetector, and a sixth light guide connected to the photodetector; 5. The wavelength-tunable light source according to any one of claims 1 to 4, wherein the second substrate has a seventh light guide path having one end connected to the fifth light guide path and the other end connected to the sixth light guide path when the first substrate is mounted on the second substrate.

[0036] [Appendix 6] 6. The tunable light source according to claim 5, wherein the seventh light guide path is formed in an area of ​​the second substrate outside the tunable block.

[0037] [Appendix 7] 7. The wavelength-tunable light source according to claim 5 or 6, wherein the light source includes a semiconductor laser.

[0038] [Appendix 8] 8. The tunable light source according to any one of claims 5 to 7, wherein the photodetector includes a semiconductor optical amplifier.

[0039] [Appendix 9] 9. The tunable light source according to any one of claims 5 to 8, wherein the first substrate is mounted on the second substrate so as to maximize the amount of light output from the light source and input to the photodetector via the fifth light guide path, the seventh light guide path, and the sixth light guide path. [Explanation of symbols]

[0040] 100: Tunable wavelength light source 120: First substrate 121: Gain Chip 122: Optical amplifier 125: First light guide 126: Second light guide 130: Second substrate 131:Tunable wavelength block 135: Third light guide 136: Fourth light guide 137: Seventh Light Guide 141: Light source 142: Fifth light guide 143: Sixth light guide 144: Photodetector

Claims

1. A wavelength tunable light source, a first substrate on which a gain chip including a first optical waveguide and an optical amplifier including a second optical waveguide are formed; a wavelength tunable block including a wavelength tunable element, and a second substrate on which a third light guide path connected to an input end of the wavelength tunable block and a fourth light guide path connected to an output end of the wavelength tunable block are formed; a tunable light source, wherein by mounting the tunable light source on the first substrate and the second substrate, the first light guide path and the third light guide path are optically coupled, and the second light guide path and the fourth light guide path are optically coupled.

2. the first light guide path and the second light guide path each extend to a first end face of the first substrate, and the third light guide path and the fourth light guide path each extend to a second end face of the second substrate; The tunable light source according to claim 1 , wherein the first substrate is mounted on the second substrate by bonding the first end face and the second end face together.

3. 3. The wavelength-tunable light source according to claim 1, wherein the first and second light guide paths are optically coupled to the third and fourth light guide paths by end-face coupling.

4. 3. The tunable light source according to claim 1, wherein the first substrate is an optical semiconductor substrate, and the second substrate is a silicon photonics substrate.

5. the first substrate further includes a light source, a fifth light guide connected to the light source, a photodetector, and a sixth light guide connected to the photodetector; 3. The wavelength-tunable light source according to claim 1, wherein the second substrate has a seventh light guide path having one end connected to the fifth light guide path and the other end connected to the sixth light guide path when the first substrate is mounted on the second substrate.

6. The tunable light source according to claim 5 , wherein the seventh light guide path is formed in an area of ​​the second substrate outside the tunable block.

7. The tunable light source of claim 5 , wherein the light source includes a semiconductor laser.

8. The tunable light source of claim 5 , wherein the photodetector comprises a semiconductor optical amplifier.

9. 6. The tunable light source according to claim 5, wherein the first substrate is mounted on the second substrate so as to maximize the amount of light output from the light source and input to the photodetector via the fifth light guide path, the seventh light guide path, and the sixth light guide path.

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