External cavity type narrow linewidth laser assembly

Abstract

The invention relates to an external cavity type narrow linewidth laser assembly comprising a substrate, the substrate is fixedly connected with a gain chip used for emitting laser, and the substrate is further connected with a first light-transmitting reflector and a second light-transmitting reflector which are sequentially arranged at intervals in the laser emitting end direction of the gain chip; the first light-transmitting reflector and the gain chip are arranged at an interval and jointly form a first outer optical resonant cavity, the second light-transmitting reflector and the first light-transmitting reflector are arranged at an interval, and the second light-transmitting reflector and the gain chip jointly form a second outer optical resonant cavity. The lengths of the first outer optical resonant cavity and the second outer optical resonant cavity of the outer cavity type narrow linewidth laser assembly are greatly increased in a limited tube shell space, and the longer the resonant cavity is, the longer the coherent light is, so that the narrower the linewidth is, and higher performance is obtained while the lower cost is kept.

Description

Technical Field

[0001] The present application relates to the field of optical communication technology, and in particular to an external cavity narrow linewidth laser component. Background Art

[0002] Semiconductor lasers have many unique advantages, such as small size, high photoelectric conversion efficiency, low driving power consumption, wide coverage, etc. However, there are also some serious shortcomings, such as wide line width. Although some semiconductor lasers can reach about 10MHz, it is far from the ideal single-mode narrow line width (sub-kHz) required by many systems.

[0003] External cavity semiconductor lasers overcome the shortcomings of ordinary semiconductor lasers, such as wide line width and poor frequency stability. They have high efficiency, long life, and stable frequency, and can be widely used in the fields of optical wave device measurement, metrology detection, water quality detection, high-resolution spectral analysis, etc.

[0004] In the related technology, external cavity type narrow linewidth lasers generally use Gain Chip chips as laser sources. The external cavity design is generally divided into two types. The first type is an integrated external chip external cavity narrow linewidth laser, and the second type is a narrow linewidth laser that uses optical components to form an external cavity.

[0005] However, the first type is more expensive due to the existence of the chip, but it has excellent performance and the intrinsic linewidth can reach the Hz level; the second type is much cheaper, but has some shortcomings in performance, and can generally make the intrinsic linewidth reach the KHz level. Summary of the invention

[0006] The embodiment of the present application provides an external cavity narrow linewidth laser component to solve the problem in the related art that external cavity semiconductor lasers with narrow intrinsic linewidth are expensive, while inexpensive external cavity semiconductor lasers have too wide intrinsic linewidth.

[0007] The embodiment of the present application provides an external cavity narrow linewidth laser assembly, comprising:

[0008] A substrate, to which a gain chip for emitting laser light is fixedly connected, and to which a first light-transmitting reflector and a second light-transmitting reflector which are arranged in sequence and spaced apart in the direction of the laser emitting end of the gain chip are also connected;

[0009] The first light-transmitting reflector is spaced apart from the gain chip and together form a first external optical resonant cavity, and the second light-transmitting reflector is spaced apart from the second light-transmitting reflector and together form a second external optical resonant cavity with the gain chip.

[0010] In some embodiments: the first light-transmitting reflector and the second light-transmitting reflector have their surfaces close to the laser emitting end of the gain chip coated with a reflective film, and the first light-transmitting reflector and the second light-transmitting reflector have their surfaces away from the laser emitting end of the gain chip coated with an anti-reflection film.

[0011] In some embodiments: the reflectivity of the first light-transmitting reflector is greater than the reflectivity of the second light-transmitting reflector, and the first light-transmitting reflector and the second light-transmitting reflector are both perpendicular to the laser emitting end of the gain chip.

[0012] In some embodiments: a collimating lens fixed on the substrate is provided between the laser emitting end of the gain chip and the first light-transmitting reflector, and the collimating lens is used to collimate the outgoing light of the laser emitting end of the gain chip into parallel light;

[0013] An etalon fixed on a substrate is provided between the collimating lens and the first light-transmitting reflector, and the etalon is used to convert the parallel light coupled by the collimating lens into multi-peak wide-spectrum parallel light with consistent free spectral range intervals.

[0014] In some embodiments: a filter fixed on the substrate is provided between the first light-transmitting reflector and the second light-transmitting reflector, and the passband range of the filter is consistent with the tuning range of the second external optical resonant cavity to suppress the laser mode outside its passband range.

[0015] In some embodiments: an isolator and a focusing lens fixed on a substrate are provided on the side of the second light-transmitting reflector facing away from the first light-transmitting reflector, the isolator is used to block the return light of the focusing lens from returning to the second external optical resonant cavity, and the focusing lens is used to focus the collimated parallel light emitted by the gain chip onto the collimating optical fiber.

[0016] In some embodiments: the collimating optical fiber is connected to a spectrometer, the substrate is provided with a slideway slidably connecting the first light-transmitting reflector and the second light-transmitting reflector, and the slideway extends along the direction of the laser emitting end of the gain chip;

[0017] The first light-transmitting reflector and the second light-transmitting reflector slide on the slideway respectively to adjust the cavity lengths of the first external optical resonant cavity and the second external optical resonant cavity, and the spectrometer displays spectral characteristics of different cavity lengths.

[0018] In some embodiments: the slide is also slidably connected to a height adjuster respectively connected to the first light-transmitting reflector and the second light-transmitting reflector, and the height adjuster is used to alternately adjust the height of the first light-transmitting reflector and the second light-transmitting reflector to match the laser modes of the first external optical resonant cavity and the second external optical resonant cavity alternately formed by the first light-transmitting reflector and the second light-transmitting reflector.

[0019] In some embodiments: a heat sink connected to the gain chip is provided on the substrate, the gain chip is attached to the heat sink by eutectic welding, the positive electrode on the surface of the gain chip is connected to one side of the heat sink by gold wire bonding, and the negative electrode on the back side of the gain chip is connected to the other side of the heat sink by bonding.

[0020] In some embodiments: the gain chip is a DFB laser, and a housing encapsulating the gain chip, the first light-transmitting reflector, and the second light-transmitting reflector is disposed on the substrate.

[0021] The beneficial effects of the technical solution provided by this application include:

[0022] An embodiment of the present application provides an external cavity narrow linewidth laser component. The external cavity narrow linewidth laser component of the present application is provided with a substrate, a gain chip for emitting laser light is fixedly connected to the substrate, and a first light-transmitting reflector and a second light-transmitting reflector which are arranged in sequence and spaced apart in the direction of the laser emitting end of the gain chip are also connected to the substrate; the first light-transmitting reflector and the gain chip are arranged spaced apart and together form a first external optical resonant cavity, and the second light-transmitting reflector and the first light-transmitting reflector are arranged spaced apart and together form a second external optical resonant cavity with the gain chip.

[0023] Therefore, the external cavity narrow linewidth laser assembly of the present application has a first light-transmitting reflector and a second light-transmitting reflector arranged in sequence in the direction of the laser emission end of the gain chip, and the first light-transmitting reflector is arranged at intervals with the gain chip and together forms a first external optical resonant cavity, and the second light-transmitting reflector is arranged at intervals with the first light-transmitting reflector and together forms a second external optical resonant cavity with the gain chip. The first external optical resonant cavity and the second external optical resonant cavity greatly increase the length of the resonant cavity within the limited tube shell space. The longer the resonant cavity length, the longer the coherent light length, and thus the narrower the linewidth, achieving higher performance while maintaining a lower cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 This is a structural front view of an embodiment of the present application;

[0026] Figure 2 A structural stereogram of an embodiment of the present application;

[0027] Figure 3This is a test spectrum diagram of an embodiment of the present application.

[0028] Reference numerals:

[0029] 1. Substrate; 2. Gain chip; 3. First light-transmitting reflector; 4. Second light-transmitting reflector; 5. First external optical resonant cavity; 6. Second external optical resonant cavity; 7. Collimating lens; 8. Standard tool; 9. Filter; 10. Isolator; 11. Focusing lens; 12. Heat sink. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0031] The embodiment of the present application provides an external cavity narrow linewidth laser component, which can solve the problem in the related art that external cavity semiconductor lasers with narrow intrinsic linewidth are expensive, while cheap external cavity semiconductor lasers have too wide intrinsic linewidth.

[0032] See also Figure 1 and Figure 2 As shown, an embodiment of the present application provides an external cavity narrow linewidth laser assembly, comprising:

[0033] A substrate 1 is provided, on which a gain chip 2 for emitting laser light is fixedly connected, and a first light-transmitting reflector 3 and a second light-transmitting reflector 4 are also connected, which are arranged in sequence and spaced apart in the direction of the laser emitting end of the gain chip 2. The first light-transmitting reflector 3 is spaced apart from the gain chip 2 and together form a first external optical resonant cavity 5, and the second light-transmitting reflector 4 is spaced apart from the first light-transmitting reflector 3 and together form a second external optical resonant cavity 6 with the gain chip 2.

[0034] The external cavity narrow linewidth laser assembly of the embodiment of the present application comprises a first light-transmitting reflector 3 and a second light-transmitting reflector 4 which are arranged in sequence in the direction of the laser emission end of the gain chip 2, and the first light-transmitting reflector 3 is arranged in intervals with the gain chip 2 and together form a first external optical resonant cavity 5, and the second light-transmitting reflector 4 is arranged in intervals with the first light-transmitting reflector 3 and together form a second external optical resonant cavity with the gain chip 2.

[0035] The first light-transmitting reflector 3 and the laser emitting end of the gain chip 2 form a first external optical resonant cavity 5 that resonates and amplifies only the target wavelength light, and the first external optical resonant cavity 5 selects the laser wavelength and continuously oscillates and amplifies it. The second light-transmitting reflector 4, the first light-transmitting reflector 3, and the laser emitting end of the gain chip 2 form a second external optical resonant cavity 6 that resonates and amplifies only the target wavelength light, and the second external optical resonant cavity 6 selects the laser wavelength and continuously oscillates and amplifies it.

[0036] The broadband light emitted by the gain chip 2 is emitted from the laser emission end and vertically incident on the first light-transmitting reflector 3. The first light-transmitting reflector 3 reflects the target wavelength and transmits the non-target light. The reflected light of the target wavelength enters the gain chip 2 and is stimulated to radiate and then reflected again. The gain chip 2 and the first light-transmitting reflector 3 form a first external optical resonant cavity 5. The gain chip 2 is combined with the first light-transmitting reflector 3 to repeatedly resonate and amplify the target light, and lasing is formed for the first time. The lasing light is output through the first light-transmitting reflector 3.

[0037] The laser light output from the first light-transmitting reflector 3 is vertically incident on the second light-transmitting reflector 4. The second light-transmitting reflector 4 reflects the target wavelength again and transmits the non-target light. The reflected light of the target wavelength passes through the first light-transmitting reflector 3 and enters the gain chip 2 for stimulated radiation and then reflects again. The gain chip 2 and the second light-transmitting reflector 4 form a second external optical resonant cavity 6. The target light is repeatedly resonated and amplified in combination with the gain chip 2 to form laser light for the second time. The laser light passes through the first light-transmitting reflector 3 and the second light-transmitting reflector 4 and is output.

[0038] The first external optical resonant cavity 5 and the second external optical resonant cavity 6 greatly increase the length of the resonant cavity within the limited tube shell space. The longer the resonant cavity length is, the longer the coherent light length is, and thus the narrower the line width is, thereby reducing the bandwidth of the resonance while maintaining a low cost, thereby realizing narrowband filtering. It has the advantages of good wavelength stability, high side mode suppression ratio, narrow line width, large adjustment tolerance, and simple manufacturing process.

[0039] In some alternative embodiments: See Figure 1 and Figure 2 As shown, an embodiment of the present application provides an external cavity narrow linewidth laser component, in which the first light-transmitting reflector 3 and the second light-transmitting reflector 4 of the external cavity narrow linewidth laser component are coated with a reflective film on one side close to the laser emitting end of the gain chip 2, and the first light-transmitting reflector 3 and the second light-transmitting reflector 4 are coated with an anti-reflection film on one side away from the laser emitting end of the gain chip 2.

[0040] The reflectivity of the first light-transmitting reflector 3 is greater than the reflectivity of the second light-transmitting reflector 4. The first light-transmitting reflector 3 and the second light-transmitting reflector 4 are perpendicular to the laser emitting end of the gain chip. The reflective films of the first light-transmitting reflector 3 and the second light-transmitting reflector 4 are used to reflect the target wavelength, and the anti-reflection films of the first light-transmitting reflector 3 and the second light-transmitting reflector 4 are used to transmit non-target light.

[0041] The reflectivity of the first light-transmitting reflector 3 is greater than that of the second light-transmitting reflector 4, so that the first external optical resonant cavity 5 formed by the first light-transmitting reflector 3 and the gain chip 2 can achieve the best oscillation state of the gain chip 2, and the spectrum formed by the first external optical resonant cavity 5 is wider and has a higher peak value.

[0042] In some alternative embodiments: See Figure 1 and Figure 2 As shown, an embodiment of the present application provides an external cavity narrow linewidth laser component, in which a collimating lens 7 fixed on a substrate 1 is provided between the laser emitting end of a gain chip 2 and a first light-transmitting reflector 3. The collimating lens 7 is used to collimate the outgoing light of the laser emitting end of the gain chip 2 and convert it into parallel light.

[0043] An etalon 8 fixed on the substrate 1 is provided between the collimating lens 7 and the first light-transmitting reflector 3. The etalon 8 is used to convert the parallel light coupled by the collimating lens 7 into multi-peak wide-spectrum parallel light with consistent free spectrum range intervals. A filter 9 fixed on the substrate 1 is provided between the first light-transmitting reflector 3 and the second light-transmitting reflector 4. The passband range of the filter 9 is consistent with the tuning range of the second external optical resonant cavity 6 to suppress the laser mode outside its passband range.

[0044] In some alternative embodiments: See Figure 1 and Figure 2 As shown, the embodiment of the present application provides an external cavity narrow linewidth laser assembly, in which the second light-transmitting reflector 4 of the external cavity narrow linewidth laser assembly is provided with an isolator 10 and a focusing lens 11 fixed on the substrate 1 on the side away from the first light-transmitting reflector 3. The isolator 10 is used to block the return light of the focusing lens 11 from returning to the second external optical resonant cavity 6 to avoid affecting the resonance performance of the second external optical resonant cavity 6. The focusing lens 11 is used to focus the collimated parallel light emitted by the gain chip 2 onto the collimating optical fiber (not shown in the figure).

[0045] In some alternative embodiments: See Figures 1 to 3As shown, an embodiment of the present application provides an external cavity narrow linewidth laser assembly, the collimating optical fiber of the external cavity narrow linewidth laser assembly is connected to a spectrometer (not shown in the figure), and a slideway (not shown in the figure) is provided on the substrate 1 for slidingly connecting the first light-transmitting reflector 3 and the second light-transmitting reflector 4, and the slideway extends along the laser emitting end direction of the gain chip 2.

[0046] The first light-transmitting reflector 3 and the second light-transmitting reflector 4 slide on the slideway respectively to adjust the cavity length of the first external optical resonant cavity 5 and the second external optical resonant cavity 6, and the spectrometer displays the spectral characteristics of different cavity lengths. The spectrometer detects and displays the spectral graph formed by the cavity lengths of the first external optical resonant cavity 5 and the second external optical resonant cavity 6 to determine the position of the first light-transmitting reflector 3 and the second light-transmitting reflector 4 from the gain chip 2.

[0047] Also slidably connected on the slide are height adjusters (not shown in the figure) respectively connected to the first light-transmitting reflector 3 and the second light-transmitting reflector 4. The height adjusters are used to alternately adjust the heights of the first light-transmitting reflector 3 and the second light-transmitting reflector 4 so that the laser modes of the first external optical resonant cavity 5 and the second external optical resonant cavity 6 alternately formed by the first light-transmitting reflector 3 and the second light-transmitting reflector 4 are matched.

[0048] A heat sink 12 connected to the gain chip 2 is provided on the substrate 1. The gain chip 2 is attached to the heat sink 12 by eutectic welding. The positive electrode on the surface of the gain chip 2 is connected to one side of the heat sink 12 by gold wire bonding, and the negative electrode on the back of the gain chip 2 is connected to the other side of the heat sink 12 by bonding. The gain chip 2 is preferably a DFB laser, which greatly reduces the overall device cost. A housing that encapsulates the gain chip 2, the first light-transmitting reflector 3, and the second light-transmitting reflector 4 is provided on the substrate 1, which is not drawn in the figure.

[0049] During testing or use, two metal probes are used to connect the positive and negative electrodes of the gain chip 2 to the power supply, and a height adjuster is used to adjust the height of the first light-transmitting reflector 3 and the second light-transmitting reflector 4 to be above the emitted light of the gain chip 2. A collimating optical fiber is used to collect light at the tail of the substrate 1. The distance between the collimating optical fiber and the gain chip 2 is fine-tuned, and the optical power is adjusted to the maximum by observing the state of the spectrum output by the spectrometer. Then, the heat sink 12 with the gain chip 2 is fixed to complete the preliminary optical coupling.

[0050] After completing the preliminary optical coupling, use the height adjuster to first place the first light-transmitting reflector 3 downward to a position close to the gain chip 2 to form the first external optical resonant cavity 5, fine-tune the first light-transmitting reflector 3 to slide on the slide, observe the spectrum pattern, so that the gain chip 2 reaches the best oscillation state and the oscillation peak matches the DFB chip peak.

[0051] Use the height adjuster to lift the first light-transmitting reflector 3 again, and place the second light-transmitting reflector 4 downward to a position farther away from the gain chip 2, and fine-tune the second light-transmitting reflector 4 to slide on the slide to form a second external optical resonant cavity 6. Observe the spectral pattern to match the mode of the second external optical resonant cavity 6 with the first external optical resonant cavity 5 to match the DFB laser chip peak.

[0052] Finally, the first light-transmitting reflector 3 is lowered by using a height adjuster, and the first light-transmitting reflector 3 and the second light-transmitting reflector 4 are fine-tuned to find a stable state, thereby completing the coupling of the key parts.

[0053] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0054] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0055] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. An external cavity narrow linewidth laser assembly, characterized in that: include: A substrate (1), a gain chip (2) for emitting laser light being fixedly connected to the substrate (1), and a first light-transmitting reflector (3) and a second light-transmitting reflector (4) being connected to the substrate (1) and being arranged in sequence and spaced apart in the direction of the laser emitting end of the gain chip (2); The first light-transmitting reflector (3) and the gain chip (2) are arranged at intervals and together form a first external optical resonant cavity (5); the second light-transmitting reflector (4) and the first light-transmitting reflector (3) are arranged at intervals and together form a second external optical resonant cavity (6) with the gain chip (2).

2. An external cavity narrow linewidth laser assembly as claimed in claim 1, characterized in that : A surface of the first light-transmitting reflector (3) and the second light-transmitting reflector (4) close to the laser emitting end of the gain chip (2) is coated with a reflective film, and a surface of the first light-transmitting reflector (3) and the second light-transmitting reflector (4) away from the laser emitting end of the gain chip (2) is coated with an anti-reflection film.

3. An external cavity narrow linewidth laser assembly as claimed in claim 1 or 2, characterized in that : The reflectivity of the first light-transmitting reflector (3) is greater than the reflectivity of the second light-transmitting reflector (4), and the first light-transmitting reflector (3) and the second light-transmitting reflector (4) are both perpendicular to the direction of the laser emitting end of the gain chip (2).

4. An external cavity narrow linewidth laser assembly as claimed in claim 1 or 2, characterized in that : A collimating lens (7) fixed on a substrate is provided between the laser emitting end of the gain chip (2) and the first light-transmitting reflector (3), and the collimating lens (7) is used to collimate the emitted light from the laser emitting end of the gain chip (2) into parallel light; An etalon (8) fixed on the substrate (1) is provided between the collimating lens (7) and the first light-transmitting reflector (3), and the etalon (8) is used to convert the parallel light coupled by the collimating lens (7) into multi-peak wide-spectrum parallel light with consistent free spectral range intervals.

5. An external cavity narrow linewidth laser assembly as claimed in claim 1 or 2, characterized in that : A filter (9) fixed on the substrate (1) is provided between the first light-transmitting reflector (3) and the second light-transmitting reflector (4); the passband range of the filter (9) is consistent with the tuning range of the second external optical resonant cavity (6) so as to suppress laser modes outside its passband range.

6. An external cavity narrow linewidth laser assembly as claimed in claim 1 or 2, characterized in that : An isolator (10) and a focusing lens (11) fixed on the substrate (1) are provided on the side of the second light-transmitting reflector (4) facing away from the first light-transmitting reflector (3); the isolator (10) is used to block the return light of the focusing lens (11) from returning to the second external optical resonant cavity (6); and the focusing lens (11) is used to focus the collimated parallel light emitted by the gain chip (2) onto the collimating optical fiber.

7. An external cavity narrow linewidth laser assembly as claimed in claim 6, characterized in that : The collimating optical fiber is connected to a spectrometer, and a slideway for slidably connecting the first light-transmitting reflector (3) and the second light-transmitting reflector (4) is provided on the substrate (1), and the slideway extends in the direction of the laser emitting end of the gain chip (2); The first light-transmitting reflector (3) and the second light-transmitting reflector (4) slide on the slideway respectively to adjust the cavity lengths of the first external optical resonant cavity (5) and the second external optical resonant cavity (6), and the spectrometer displays spectral characteristics of different cavity lengths.

8. An external cavity narrow linewidth laser assembly as claimed in claim 7, characterized in that : The slideway is also slidably connected to a height adjuster respectively connected to the first light-transmitting reflector (3) and the second light-transmitting reflector (4), and the height adjuster is used to alternately adjust the height of the first light-transmitting reflector (3) and the second light-transmitting reflector (4) so ​​as to match the laser modes of the first external optical resonant cavity (5) and the second external optical resonant cavity (6) alternately formed by the first light-transmitting reflector (3) and the second light-transmitting reflector (4).

9. An external cavity narrow linewidth laser assembly as claimed in claim 1 or 2, characterized in that : A heat sink (12) connected to the gain chip (2) is provided on the substrate (1); the gain chip (2) is attached to the heat sink (12) by eutectic welding; the positive electrode on the surface of the gain chip (2) is connected to one side of the heat sink (12) by gold wire bonding; and the negative electrode on the back side of the gain chip (2) is connected to the other side of the heat sink (12) by bonding.

10. An external cavity narrow linewidth laser assembly as claimed in claim 1 or 2, characterized in that : The gain chip (2) is a DFB laser, and a housing for packaging the gain chip (2), a first light-transmitting reflector (3), and a second light-transmitting reflector (4) is provided on the substrate (1).

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