Annular narrow linewidth laser and control method

Abstract

The invention relates to an annular narrow linewidth laser and a control method. The annular narrow linewidth laser comprises a semiconductor laser, a fiber bragg grating, an optical splitter, a light outlet and a self-excited current regulator, the semiconductor laser is provided with a first coupling end, a second coupling end and an inner resonant cavity, the first coupling end is plated with an antireflection film, and the second coupling end is plated with a high-reflection film; the first coupling end, the fiber bragg grating, the low-proportion output end and the second coupling end are sequentially coupled to form an annular light path; a first Fabry-Perot resonant cavity is formed between one end of the fiber bragg grating and the high-reflective film, and a second Fabry-Perot resonant cavity is formed between the other end of the fiber bragg grating and the high-reflective film; the self-excited current regulator is used for tuning the current injected into the semiconductor laser, so that the oscillation frequency of the semiconductor laser, the oscillation frequency of the first Fabry-Perot resonant cavity and the oscillation frequency of the second Fabry-Perot resonant cavity are consistent, line width narrowing is achieved, and the self-excited current regulator has the advantages of narrowing the line width, increasing light emitting power and being easy to package.

Description

Technical Field

[0001] The present invention relates to the technical field of lasers, and in particular to a ring-shaped narrow-linewidth laser and a control method thereof. Background Art

[0002] With the development of coherent optical communication, lidar, wind radar, medical photons, and long-distance sensing, the line width requirements of the lasers used are getting narrower and narrower. At present, the mainstream method to achieve line width narrowing is the hybrid integration of semiconductor lasers and silicon-based external cavities. It mainly uses high-quality factor external cavities, such as silicon-based microrings and silicon-based Bragg gratings. The above methods can achieve good line width narrowing effects, even reaching the Hz level. However, its disadvantages are also obvious, such as:

[0003] 1) The hybrid integrated packaging process of silicon-based external cavity and semiconductor laser is not yet mature, and the packaging cost is relatively high;

[0004] 2) Because of the additional phase shift function, its power consumption is too large;

[0005] 3) Too much light is lost in hybrid integration, resulting in the hybrid integrated laser's output power being generally low.

[0006] Based on the shortcomings of the above technologies, we proposed a ring-shaped narrow-linewidth laser and a control method. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the defects in the prior art, thereby providing a ring-shaped narrow-linewidth laser and a control method.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A ring-shaped narrow linewidth laser comprises a semiconductor laser, a fiber Bragg grating, a beam splitter, a light outlet and a self-excited current regulator;

[0010] The semiconductor laser comprises a first coupling end, a second coupling end and an internal resonant cavity, the first coupling end is coated with an anti-reflection film, and the second coupling end is coated with a high-reflection film;

[0011] The optical splitter comprises a low-ratio output end and a high-ratio output end, and the high-ratio output end is coupled to the light outlet;

[0012] The first coupling end, the fiber Bragg grating, the low-ratio output end, and the second coupling end are coupled in sequence to form a ring optical path;

[0013] The fiber Bragg grating is used to reflect the forward light coupled out by the first coupling end, and is also used to reflect the reverse light coupled out by the second coupling end;

[0014] A first Fabry-Perot resonant cavity is formed between one end of the fiber Bragg grating and the high-reflection film; a second Fabry-Perot resonant cavity is formed between the other end of the fiber Bragg grating and the high-reflection film, and the first Fabry-Perot resonant cavity and the second Fabry-Perot resonant cavity have different cavity lengths;

[0015] The self-excited current regulator is used to tune the current injected into the semiconductor laser so as to make the oscillation frequency of the semiconductor laser, the oscillation frequency of the first Fabry-Perot resonant cavity and the oscillation frequency of the second Fabry-Perot resonant cavity consistent, thereby achieving line width narrowing.

[0016] Preferably, it also includes a first optical fiber and a second optical fiber; one end of the first optical fiber is coupled and docked with the first coupling end, and the other end is coupled and docked with one end of the second optical fiber through the low-ratio output end, and the other end of the second optical fiber is coupled and docked with the second coupling end.

[0017] Preferably, the first optical fiber is coupled to the semiconductor laser via a lens; and / or the second optical fiber is coupled to the semiconductor laser via a lens.

[0018] Preferably, the first optical fiber is configured as a lens optical fiber or a cleaved optical fiber, and / or the second optical fiber is configured as a lens optical fiber or a cleaved optical fiber.

[0019] Preferably, the reflectivity of the anti-reflection film is less than 1%; and the reflectivity of the high-reflection film is greater than 90%.

[0020] Preferably, the light splitting ratio between the low-ratio output end and the high-ratio output end is any one of 5% / 95%, 10% / 90%, and 20% / 80%.

[0021] A control method for a ring-shaped narrow linewidth laser based on the above-mentioned method, the ring-shaped narrow linewidth laser comprises a semiconductor laser, a fiber Bragg grating, a beam splitter, a light outlet and a self-excited current regulator, the semiconductor laser comprises a first coupling end, a second coupling end and an internal resonant cavity, the first coupling end is plated with an anti-reflection film, the second coupling end is plated with a high-reflection film, a first Fabry-Perot resonant cavity is formed between the fiber Bragg grating and the high-reflection film; a second Fabry-Perot resonant cavity is formed between the fiber Bragg grating and the high-reflection film, the first Fabry-Perot resonant cavity and the second Fabry-Perot resonant cavity have different cavity lengths; the control method comprises the following steps: injecting a preset current into the semiconductor laser so that the semiconductor laser outputs a preset output light; tuning the preset current injected into the semiconductor laser so that the oscillation frequency of the semiconductor laser, the oscillation frequency of the first Fabry-Perot resonant cavity and the oscillation frequency of the second Fabry-Perot resonant cavity are consistent to achieve linewidth narrowing; and outputting narrow linewidth laser through the light outlet.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] In the above technical solution, a ring-shaped narrow linewidth laser is provided, wherein the first coupling end, the fiber Bragg grating, the low-ratio output end, and the second coupling end are coupled and docked in sequence to form a ring optical path, so that the phase of the light in the narrow linewidth laser is always matched, and no additional phase shift function is required, thereby reducing the power consumption of the entire laser. In addition, the optical loss of the optical fiber is 5 orders of magnitude smaller than that of the silicon-based material, and the maturity of the semiconductor laser and optical fiber coupling process can avoid excessive loss of light during the hybrid integration process, thereby increasing the output power of the laser. In addition, compared with the existing silicon-based microring and silicon-based Bragg grating lasers, this solution does not need to set a phase shift structure, and the overall structure is simple, which is compatible with the existing semiconductor laser packaging process and is convenient for laser packaging. At the same time, by forming a first Fabry-Perot resonant cavity between the fiber Bragg grating and the high-reflection film, and forming a second Fabry-Perot resonant cavity between the fiber Bragg grating and the high-reflection film, the lengths of the first Fabry-Perot resonant cavity and the second Fabry-Perot resonant cavity can be different, and the corresponding FP mode intervals will also be different, which will produce an optical cursor effect. When the current injected into the semiconductor laser is tuned by the self-excited current regulator, the oscillation frequency of the inner resonant cavity of the semiconductor laser is consistent with the oscillation frequency of the first Fabry-Perot cavity and the oscillation frequency of the second Fabry-Perot cavity formed in the annular optical path, the line width can be narrowed. Correspondingly, the control method based on the above-mentioned annular narrow line width laser has the advantages of narrowing the line width, increasing the light output power, and simple packaging. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0025] Figure 1 This is a schematic diagram of the structure of the narrow linewidth laser provided by the present invention.

[0026] Figure 2 Schematic diagram of the optical vernier effect.

[0027] Figure 3 This is a line width test diagram in one embodiment.

[0028] Description of reference numerals:

[0029] 1. Semiconductor laser; 11. First coupling end; 12. Second coupling end; 2. Fiber Bragg grating; 3. Optical splitter; 31. Low-ratio output end; 32. High-ratio output end; 4. Light outlet; 5. First optical fiber; 6. Second optical fiber. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention 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 limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that, 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 indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] See also Figures 1 to 3 The embodiment of the present invention provides a ring narrow linewidth laser, including a semiconductor laser 1, a fiber Bragg grating 2, a beam splitter 3, a light outlet 4 and a self-excited current regulator.

[0034] Specifically, the semiconductor laser 1 has a first coupling end 11, a second coupling end 12 and an internal resonant cavity, the first coupling end 11 is coated with an anti-reflection film, and the second coupling end 12 is coated with a high-reflection film; the optical splitter 3 includes a low-ratio output end 31 and a high-ratio output end 32, and the high-ratio output end 32 is coupled to the light outlet 4; the first coupling end 11, the fiber Bragg grating 2, the low-ratio output end 31, and the second coupling end 12 are coupled in sequence to form a ring optical path; the fiber Bragg grating 2 is used to reflect the clockwise light coupled out of the first coupling end 11, and is also used to reflect the clockwise light of the second coupling end 12 coupled output reverse light; a first Fabry-Perot resonant cavity is formed between one end of the fiber Bragg grating 2 and the high reflection film; a second Fabry-Perot resonant cavity is formed between the other end of the fiber Bragg grating 2 and the high reflection film, and the first Fabry-Perot resonant cavity and the second Fabry-Perot resonant cavity have different cavity lengths; a self-excited current regulator is used to tune the current injected into the semiconductor laser 1 so that the oscillation frequency of the semiconductor laser 1, the oscillation frequency of the first Fabry-Perot resonant cavity and the oscillation frequency of the second Fabry-Perot resonant cavity are consistent, so as to achieve line width narrowing.

[0035] In this embodiment, the first coupling end 11, the fiber Bragg grating 2, the low-ratio output end 31, and the second coupling end 12 are coupled and docked in sequence to form a ring optical path, so that the phase of the light in the narrow linewidth laser is always matched, and there is no need to use an additional phase shift function, which reduces the power consumption of the entire laser. In addition, the optical loss of the optical fiber is 5 orders of magnitude smaller than that of the silicon-based material, and the maturity of the semiconductor laser and optical fiber coupling process can avoid excessive loss of light in the hybrid integration process, thereby increasing the output power of the laser. In addition, compared with the existing silicon-based microring and silicon-based Bragg grating lasers, this solution does not need to set a phase shift structure, the overall structure is simple, and it is compatible with the existing semiconductor laser 1 packaging process, which is convenient for laser packaging. At the same time, a first Fabry-Perot resonant cavity is formed between the fiber Bragg grating 2 and the high-reflection film; a second Fabry-Perot resonant cavity is formed between the fiber Bragg grating 2 and the high-reflection film, so that the lengths of the first Fabry-Perot resonant cavity and the second Fabry-Perot resonant cavity are different, and the corresponding FP mode intervals will also be different, which will produce an optical vernier effect. When the current injected into the semiconductor laser 1 is tuned by the self-excited current regulator so that the oscillation frequency of the inner resonant cavity of the semiconductor laser 1 is consistent with the oscillation frequency of the first Fabry-Perot cavity and the oscillation frequency of the second Fabry-Perot cavity formed in the ring optical path, line width narrowing can be achieved.

[0036] See also Figure 1 In this embodiment, the annular narrow linewidth laser further includes a first optical fiber 5 and a second optical fiber 6. One end of the first optical fiber 5 is coupled and docked with the first coupling end 11, and the other end is coupled and docked with one end of the second optical fiber 6 through the low-ratio output end 31, and the other end of the second optical fiber 6 is coupled and docked with the second coupling end 12. The maturity of the semiconductor laser and optical fiber coupling process can avoid excessive light loss in the hybrid integration process, thereby increasing the output power of the laser.

[0037] Specifically, the first optical fiber 5 is coupled to the semiconductor laser 1 through a lens, and the second optical fiber 6 is coupled to the semiconductor laser 1 through a lens.

[0038] Furthermore, the fiber Bragg grating 2 is manufactured on the first optical fiber 5 .

[0039] Furthermore, the first optical fiber 5 can be configured as a lens optical fiber or a cleaved optical fiber, and the second optical fiber 6 can also be configured as a lens optical fiber or a cleaved optical fiber.

[0040] In this embodiment, the reflectivity of the anti-reflection film is less than 1%; the reflectivity of the high-reflection film is greater than 90%.

[0041] In this embodiment, the light splitting ratio between the low-ratio output end 31 and the high-ratio output end 32 can be set to 5% / 95%, 10% / 90% or 20% / 80%.

[0042] As can be seen from the above, when the narrow linewidth laser is in use, a certain value of current is injected into the semiconductor laser 1, so that the semiconductor laser 1 emits light of a certain frequency, wherein part of the light emitted by the semiconductor laser 1 is coupled into the first optical fiber 5. For the convenience of description, this part of the light is called forward light. The forward light passes through the fiber Bragg grating 2, a small part of it is reflected back to the semiconductor laser 1 through the fiber Bragg grating 2, and most of it is transmitted to the optical splitter 3 through the fiber Bragg grating 2. Most of the forward light transmitted to the optical splitter 3 is output through the high-ratio output end 32 and the light outlet 4. Part of the light emitted by the semiconductor laser 1 is coupled into the second optical fiber 6. For the convenience of description, this part of the light is called reverse light. After a part of the reverse light passes through the optical splitter 3, it is reflected back to the semiconductor laser 1 through the fiber Bragg grating 2.

[0043] It can be known that, at this time, the semiconductor laser 1, the first optical fiber 5, the optical splitter 3, and the second optical fiber 6 form a ring optical path. Figure 1 and Figure 2 In the forward light path, the high-reflection film of the semiconductor laser 1 and the fiber Bragg grating 2 form the first Fabry-Perot resonant cavity; in the reverse light path, the high-reflection film of the semiconductor laser 1 and the fiber Bragg grating 2 form the second Fabry-Perot resonant cavity; the lengths of the inner resonant cavity of the semiconductor laser 1, the first Fabry-Perot resonant cavity, and the second Fabry-Perot resonant cavity are different, and for λ1, the FP mode interval Δλ2 of the first Fabry-Perot resonant cavity and λ3 of the second Fabry-Perot resonant cavity will also be different, thereby generating an optical vernier effect. By tuning the current injected into the semiconductor laser 1, λ1, the oscillation frequency λ2 of the first Fabry-Perot resonant cavity, and the oscillation λ3 of the second Fabry-Perot resonant cavity are kept consistent, the line width can be narrowed.

[0044] Further, see Figure 3 , Figure 3 This is the line width test chart. The integrated line width of about 7 kHz was measured using the delayed self-heterodyne method, and the optical power was about 15 dBm.

[0045] The present application also provides a control method based on the above-mentioned ring narrow linewidth laser, which specifically includes the following steps:

[0046] Injecting a preset current into the semiconductor laser 1 so that the semiconductor laser 1 outputs a preset output light;

[0047] Tuning the preset current injected into the semiconductor laser 1 so that the oscillation frequency of the semiconductor laser 1, the oscillation frequency of the first Fabry-Perot resonant cavity and the oscillation frequency of the second Fabry-Perot resonant cavity are consistent, thereby achieving line width narrowing;

[0048] The narrow line width laser is outputted through the light outlet 4 .

[0049] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A ring-shaped narrow linewidth laser, characterized in that: It comprises a semiconductor laser (1), a fiber Bragg grating (2), a beam splitter (3), a light outlet (4) and a self-excited current regulator; The semiconductor laser (1) comprises a first coupling end (11), a second coupling end (12) and an internal resonant cavity, the first coupling end (11) being plated with an anti-reflection film, and the second coupling end (12) being plated with a high-reflection film; The optical splitter (3) comprises a low-ratio output end (31) and a high-ratio output end (32), and the high-ratio output end (32) is coupled to the light output port (4); The first coupling end (11), the fiber Bragg grating (2), the low-ratio output end (31), and the second coupling end (12) are coupled in sequence to form a ring optical path; The fiber Bragg grating (2) is used to reflect the forward light coupled out by the first coupling end (11), and is also used to reflect the reverse light coupled out by the second coupling end (12); A first Fabry-Perot resonant cavity is formed between one end of the fiber Bragg grating (2) and the high-reflection film, and a second Fabry-Perot resonant cavity is formed between the other end and the high-reflection film, wherein the first Fabry-Perot resonant cavity and the second Fabry-Perot resonant cavity have different cavity lengths; The self-excited current regulator is used to tune the current injected into the semiconductor laser (1) so as to make the oscillation frequency of the semiconductor laser (1), the oscillation frequency of the first Fabry-Perot resonant cavity and the oscillation frequency of the second Fabry-Perot resonant cavity consistent, thereby achieving line width narrowing.

2. The ring-shaped narrow linewidth laser according to claim 1, characterized in that: Also includes a first optical fiber (5) and a second optical fiber (6); One end of the first optical fiber (5) is coupled and docked with the first coupling end (11), and the other end is coupled and docked with one end of the second optical fiber (6) through the low-ratio output end (31), and the other end of the second optical fiber (6) is coupled and docked with the second coupling end (12).

3. The ring-shaped narrow linewidth laser according to claim 2, characterized in that: The fiber Bragg grating (2) is manufactured on the first optical fiber (5).

4. The ring-shaped narrow linewidth laser according to claim 2, characterized in that: The first optical fiber (5) is coupled to the semiconductor laser (1) via a lens; and / or, The second optical fiber (6) is coupled to the semiconductor laser (1) via a lens.

5. The ring-shaped narrow linewidth laser according to claim 2, characterized in that: The first optical fiber (5) is configured as a lens optical fiber or a cleaved optical fiber, and / or, The second optical fiber (6) is configured as a lens optical fiber or a cleaved optical fiber.

6. A ring-shaped narrow linewidth laser according to any one of claims 1 to 5, characterized in that: The reflectivity of the antireflection film is less than 1%; The reflectivity of the high-reflective film is greater than 90%.

7. A ring-shaped narrow linewidth laser according to any one of claims 1 to 5, characterized in that: The light splitting ratio between the low-ratio output end (31) and the high-ratio output end (32) is selected from any one of 5% / 95%, 10% / 90%, and 20% / 80%.

8. A control method for a ring narrow linewidth laser according to any one of claims 1 to 7, characterized in that: The annular narrow linewidth laser comprises a semiconductor laser (1), a fiber Bragg grating (2), a beam splitter (3), a light outlet (4) and a self-excited current regulator. The semiconductor laser (1) has a first coupling end (11), a second coupling end (12) and an internal resonant cavity. The first coupling end (11) is coated with an anti-reflection film, and the second coupling end (12) is coated with a high-reflection film. A first Fabry-Perot resonant cavity is formed between the fiber Bragg grating (2) and the high-reflection film; a second Fabry-Perot resonant cavity is formed between the fiber Bragg grating (2) and the high-reflection film. The first Fabry-Perot resonant cavity and the second Fabry-Perot resonant cavity have different cavity lengths. The control method comprises the following steps: Injecting a preset current into the semiconductor laser (1) so that the semiconductor laser (1) outputs a preset output light; Tuning a preset current injected into the semiconductor laser (1) so that the oscillation frequency of the semiconductor laser (1), the oscillation frequency of the first Fabry-Perot resonant cavity and the oscillation frequency of the second Fabry-Perot resonant cavity are consistent, thereby achieving line width narrowing; Laser light with a narrow line width is output through the light outlet (4).

Images