Packaging structure of distributed feedback fiber laser

Abstract

The invention relates to the technical field of fiber bragg grating lasers, in particular to a packaging structure of a distributed feedback fiber laser, the distributed feedback fiber laser is attached to a V-shaped groove in a packaging body, a TEC array is arranged below the V-shaped groove, and the temperature of the TEC array is controlled through a temperature control module. The V-groove structure with the arc-shaped bottom is tightly attached to the phase-shift fiber bragg grating, the TECs with independent temperature control are arranged at the bottom of the structure, and a distributed thermal field is generated through a TEC array to perform compensation temperature control on a non-uniform heating thermal field of the DFB-FL, so that the phase-shift fiber bragg grating structure still tends to be uniform during pumping work; and therefore, the problems of reduced laser efficiency and unstable line width caused by thermally induced chirp when the DFB-FL works can be eliminated.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber grating lasers, and in particular to a packaging structure of a distributed feedback fiber laser. Background Art

[0002] Distributed feedback fiber laser (DFB-FL) uses an active π-phase-shifted fiber Bragg grating to form a distributed feedback resonant cavity. It has the advantages of intrinsic single longitudinal mode, narrow linewidth, and low noise. It is widely used in technical fields such as fiber optic hydrophones, lidar, and high-precision fiber optic sensing.

[0003] The DFB-FL has a remarkably slender structure with an aspect ratio far greater than 150. Its distributed feedback resonator and laser gain medium are completely superimposed on the π-phase-shifted fiber Bragg grating structure. Therefore, the effects of environmental vibration and temperature changes on the grating structure can easily cause instability in the DFB-FL's output characteristics, such as efficiency, linewidth, and noise.

[0004] To address these issues, the utility model patent with authorization publication number CN205377008U proposes a narrow-linewidth fiber laser packaging device that uses a semiconductor cooler for active temperature control, combined with aerogel insulation material, to minimize the impact of temperature changes on laser stability. The invention patent with authorization publication number CN116646807B proposes a narrow-linewidth fiber laser packaging device that uses a semiconductor cooler and an air circulation drive mechanism for forced convection to dissipate heat from the narrow-linewidth fiber laser. However, forced air flow can cause local airflow disturbances, affecting the thermal field balance within the fiber laser resonator. This can cause laser frequency drift, particularly under high-frequency vibration or rapid temperature changes. The invention patent with application publication number CN103050872A proposes a product comprising a certain length of optical fiber and a packaging body. This product achieves acoustic and vibration isolation for the fiber laser by providing a carrier surface that is convex in the longitudinal direction of the optical fiber, which supports the optical fiber including a fiber Bragg grating. However, it does not examine the disturbance of the fiber Bragg grating structure caused by uneven thermal field distribution within the resonator during fiber laser operation.

[0005] The above work is all carried out to address the impact of ambient temperature vibration on DFB-FL. In addition, DFB-FL itself will generate heat after being excited by pump light (fibers with different gain media and doping concentrations will generate heat differently). The thermal field distribution generated by this heat is attenuated to both sides with the grating π phase shift point as the highest temperature point. This causes the π phase shift fiber grating period to generate thermal chirp with temperature distribution to a certain extent, thereby breaking the structural stability of the distributed feedback resonant cavity. The thermal imager actually detected that the temperature difference in the grating area of ​​40mm long erbium-doped fiber DFB-FL during operation reached more than 2°C. Figure 1Therefore, DFB-FL has obvious thermal chirp problem in actual operation, which may cause the efficiency and noise level of narrow linewidth laser to be suboptimal. There are few targeted studies on this issue.

[0006] To this end, the present application proposes a packaging structure for a distributed feedback fiber laser, which utilizes a V-groove structure with an arc-shaped bottom to tightly fit a phase-shifted fiber Bragg grating. Multiple TECs with independent temperature control are arranged at the bottom of the structure. The distributed thermal field generated by the TEC array is used to compensate for the uneven heating field of the DFB-FL itself, so that the phase-shifted fiber Bragg grating structure remains uniform during pumping operation, thereby eliminating the problems of reduced laser efficiency and unstable linewidth caused by thermally induced chirp during DFB-FL operation. Summary of the Invention

[0007] In order to make up for the deficiencies in the prior art, the present invention provides a packaging structure for a distributed feedback fiber laser.

[0008] A packaging structure for a fabric feedback fiber laser includes a packaging body, characterized in that: A distributed feedback fiber laser is attached to the V-groove in the package body, and a TEC array is arranged below the V-groove. The temperature of the TEC array is controlled by a temperature control module.

[0009] Furthermore, in order to better implement the present invention, the convex arc shape of the V-shaped groove fits the distributed feedback fiber laser, so that the entire distributed feedback resonant cavity presents a convex arc shape.

[0010] Furthermore, in order to better implement the present invention, the parts where the two ends of the distributed feedback fiber laser contact the packaging body are glue points, and UV glue is used to glue and fix the distributed feedback fiber laser at the glue points.

[0011] Furthermore, in order to better implement the present invention, thermal conductive silicone grease is applied to the convex arc portion of the V-shaped groove to assist in heat dissipation and fixation of the distributed feedback fiber laser.

[0012] Furthermore, in order to better implement the present invention, the TEC array is composed of 5 TEC sheets, which are arranged in sequence from the pump end to the output end below the convex arc V-groove, and the 5 TEC sheets are all connected to a five-channel temperature control module.

[0013] Furthermore, in order to better implement the present invention, the five TEC pieces are arranged in the order of the fourth TEC piece, the second TEC piece, the first TEC piece, the third TEC piece and the fifth TEC piece from the pump end to the output end; The temperature control module controls the temperature of the fourth TEC plate and the fifth TEC plate to be consistent and set to 27°C; the temperature control module controls the temperature of the second TEC plate and the third TEC plate to be consistent and set to 26°C; the first TEC plate is set directly below the π phase shift point of the distributed feedback fiber laser, corresponding to the highest point of the internal thermal field when the distributed feedback fiber laser emits laser, and the first TEC plate is set to the lowest temperature, set to 25°C.

[0014] The beneficial effects of the present invention are: The present invention utilizes a V-groove structure with an arc-shaped bottom to tightly fit a phase-shifted fiber Bragg grating (FBG). Multiple independently temperature-controlled TECs are disposed at the bottom of the structure. The TEC array generates a distributed thermal field to compensate for the uneven heating field of the DFB-FL itself, thereby ensuring that the phase-shifted fiber Bragg grating structure remains uniform during pumping operation, thereby eliminating the problems of reduced laser efficiency and unstable linewidth caused by thermally induced chirp during DFB-FL operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the grating region temperature when the distributed feedback fiber laser is working; Figure 2 Schematic diagram of the temperature difference inside the distributed feedback fiber laser; Figure 3 This is a schematic diagram of the packaging structure of the distributed feedback fiber laser of the present invention; Figure 4 This is the thermal field distribution diagram of the distributed feedback fiber laser before and after packaging of the present invention; Figure 5 This is a comparison chart of the output laser slope efficiency of the distributed feedback fiber laser before and after packaging of the present invention.

[0016] In the figure, 1. Semiconductor pump source, 2. Wavelength division multiplexer, 3. Package body, 4. Distributed feedback fiber laser, 5. TEC array, 6. Glue point, 7. Temperature control module, 8. Optical isolator, 51. First TEC plate, 52. Second TEC plate, 53. Third TEC plate, 54. Fourth TEC plate, 55. Fifth TEC plate. DETAILED DESCRIPTION

[0017] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in a variety of different configurations.

[0018] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely intended to represent selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0019] Figure 1-Figure 5 This is a specific embodiment of the present invention, which is a package structure for a distributed feedback fiber laser. A distributed feedback fiber laser is composed of an active fiber (doped with lanthanum rare earth elements such as erbium, ytterbium, thulium, and holmium, or co-doped with them) and a π-phase-shifted grating, forming a distributed feedback resonant cavity and providing laser gain. Under the action of pump light, heat is generated on the active grating, and the heat is attenuated toward both sides, with the π-phase-shifted point as the highest temperature point and center. This causes the fiber grating period to chirp, as shown in the following example. Figure 2 As shown, this further leads to obvious problems such as low output efficiency and noise degradation of distributed feedback fiber lasers.

[0020] This application proposes a packaging structure for temperature-controlled compensation of periodic thermal chirp of phase-shifted fiber Bragg gratings. First, a convex arc-shaped V-groove structure is used to encapsulate the DFB-FL. The V-groove structure fits the fiber Bragg grating tightly, forming a more effective heat exchange mechanism. Secondly, a gradient thermal field is constructed at different positions of the fiber Bragg grating through an independently temperature-controlled TEC array. This thermal field can compensate for the thermal field distribution law generated by the DFB-FL pump itself, such as Figure 3 As shown in the figure, precise temperature control enables the DFB-FL to maintain a uniform fiber Bragg grating state even at different pump powers, thereby improving laser efficiency and stable linewidth.

[0021] The upper half of the package structure body 3 features a V-groove with a convex bottom for accommodating the distributed feedback fiber laser 4. The lower half features several gaps for accommodating the TEC array 4. The package structure body 3 can be made of metal materials such as copper and aluminum to facilitate heat exchange management. The distributed feedback fiber laser 4 is made of lanthanide rare earth ion fiber, pre-stretched to a specific wavelength, and then bonded to the package structure body 3 using glue dots 6. The active phase-shift grating is attached to the bottom of the V-groove. The bottom of the V-groove is a convex arc structure with a radius generally greater than 0.5 meters. The lower half of the package structure body 3 features gaps of a number and size matching those of the TEC array 5, which are placed in these gaps. The TEC array 5 is temperature-controlled by a temperature control module 7.

[0022] When the distributed feedback fiber laser 4 operates under semiconductor pump light excitation and emits narrow-linewidth laser light, the phase-shift grating generates heat. This heat creates a thermal field distribution with the highest temperature at the π phase-shift point of the grating decaying toward both sides, causing periodic thermal chirp of the grating. The temperature control module 7 independently controls the temperature of each TEC in the TEC array 5, creating a thermal field distribution with a low temperature in the center and high temperatures on both sides. This temperature-controlled compensation compensates for the phase-shift grating's own thermal field, eliminating the thermal chirp and ensuring that the DFB-FL operates with a uniform period.

[0023] The packaging structure of the distributed feedback fiber laser of this embodiment utilizes a convex arc-shaped V-groove with higher heat transfer efficiency to limit and package the fiber Bragg grating laser. A controllable thermal field distribution is constructed by temperature-controlling multiple TECs separately. This compensates for the thermal gradient distribution on the π-phase-shifted fiber Bragg grating during operation of the distributed feedback fiber laser, eliminates the problem of thermal chirp, ensures thermal field balance within the distributed feedback resonant cavity, and enables the distributed feedback fiber laser to achieve higher output power and efficiency.

[0024] The specific implementation of this embodiment is as follows: This embodiment utilizes a distributed feedback fiber laser packaging structure to achieve the goal of higher efficiency and more stable laser emission from the distributed feedback fiber laser. A 40mm phase-shifted fiber Bragg grating with a phase shift of π is written on a 250μm diameter ytterbium-doped fiber using a grating writing system to form an ytterbium-doped distributed feedback fiber laser. During the writing process, the grating period except for the phase shift point is controlled to remain consistent. Under natural conditions, a 200mW pump light is applied to the ytterbium-doped distributed feedback fiber laser, causing stimulated radiation in its distributed feedback resonant cavity and emitting laser light. A thermal imager is used to perform a temperature test on the ytterbium-doped distributed feedback fiber laser, and it is detected that the thermal field temperature of the 40mm long ytterbium-doped distributed feedback fiber laser is as high as 27.2°C near the phase shift point and as low as 24.9°C at both ends of the distributed feedback resonant cavity, with a temperature difference of more than 2°C. This thermal field distribution will cause thermal chirp of the π phase-shifted fiber Bragg grating and change the grating period. The thermal field distribution in the distributed feedback resonant cavity is recorded at this time, and the slope efficiency of the ytterbium-doped distributed feedback fiber laser is tested using a power meter and the data is recorded. The ytterbium-doped distributed feedback fiber laser is then placed in the distributed feedback fiber laser packaging structure for packaging.

[0025] like Figure 3As shown, the Ytterbium-doped distributed feedback fiber laser 4 is placed in the convex arc V-groove. The Ytterbium-doped distributed feedback fiber laser 4 fits the convex arc V-groove, giving the entire distributed feedback resonant cavity a convex arc shape. The areas where the two ends of the Ytterbium-doped distributed feedback fiber laser 4 contact the package body 3 are glue points 6. UV glue is used to glue the Ytterbium-doped distributed feedback fiber laser 4 to the glue points 6. Thermal grease is evenly applied to the convex arc V-groove to assist in heat dissipation and fixation of the ytterbium-doped distributed feedback fiber laser 4; five TEC plates are arranged in sequence from the pump end to the output end below the convex arc V-groove to form a TEC array 5, and are divided into TEC plates 51, TEC plates 52, TEC plates 53, TEC plates 54, and TEC plates 55 according to different positions. When pumping is applied to the ytterbium-doped distributed feedback fiber laser 4, the temperatures of the TEC plates 54 and 55 are controlled to be consistent through the five-channel temperature control module 7, and are set to 27°C; the temperatures of the TEC plates 52 and 53 are consistent and are set to 26°C. The TEC plate 51 is set directly below the π phase shift point of the ytterbium-doped distributed feedback fiber laser 4, corresponding to the highest point of the internal thermal field when the ytterbium-doped distributed feedback fiber laser 4 emits laser light. The TEC plate 51 is set to the lowest temperature, which is set to 25°C. Figure 3 This achieves gradient control of the thermal field of the ytterbium-doped distributed feedback fiber laser, maintains uniform thermal field distribution within the distributed feedback resonant cavity, and maintains the uniform and stable structure of the π-phase-shifted fiber Bragg grating.

[0026] Under 200mW pump power, the Yb-doped distributed feedback fiber laser was subjected to thermal field tests in the natural state before packaging and after packaging. Figure 4 As shown in the figure, the results show that the thermal field distribution of the Yb-doped distributed feedback fiber laser after packaging is more uniform; the Yb-doped distributed feedback fiber laser is subjected to a minimum of 25mW and a maximum of 300mW pump light, and the output laser slope efficiency of the Yb-doped distributed feedback fiber laser is tested in the natural state and after packaging. Figure 5 As shown, the results show that the laser output slope efficiency of the packaged ytterbium-doped distributed feedback fiber laser is better, indicating that this device can effectively achieve isothermal approach inside the distributed feedback resonant cavity, improve the output laser efficiency of the ytterbium-doped distributed feedback fiber laser, and achieve the goal of higher output power and more stable laser of the distributed feedback fiber laser.

[0027] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A packaging structure for a fabric feedback fiber laser, comprising a packaging body (3), characterized in that: A distributed feedback fiber laser (4) is bonded to the V-shaped groove in the package body (3), and a TEC array (5) is provided below the V-shaped groove. The temperature of the TEC array (5) is controlled by a temperature control module (7).

2. The packaging structure of the fabric feedback fiber laser according to claim 1, characterized in that: The convex arc shape of the V-shaped groove fits the distributed feedback fiber laser (4), so that the entire distributed feedback resonant cavity presents a convex arc shape.

3. The packaging structure of the fabric feedback fiber laser according to claim 2, characterized in that: The portions where both ends of the distributed feedback fiber laser (4) contact the packaging body (3) are glue points (6), and UV glue is used to glue and fix the distributed feedback fiber laser (4) at the glue points (6).

4. The packaging structure of the fabric feedback fiber laser according to claim 2, characterized in that: Thermal conductive silicone grease is applied to the convex arc portion of the V-shaped groove to assist in heat dissipation and fixation of the distributed feedback fiber laser (4).

5. The packaging structure of the fabric feedback fiber laser according to claim 1, characterized in that: The TEC array (5) is composed of five TEC sheets, which are arranged in sequence from the pump end to the output end below the convex arc V-shaped groove, and the five TEC sheets are connected to a five-channel temperature control module (7).

6. The packaging structure of the fabric feedback fiber laser according to claim 5, characterized in that: The five TEC plates are arranged in the order of the fourth TEC plate (54), the second TEC plate (52), the first TEC plate (51), the third TEC plate (53) and the fifth TEC plate (55) from the pump end to the output end; The temperature control module (7) controls the temperatures of the fourth TEC plate (54) and the fifth TEC plate (55) to be consistent; the temperature control module (7) controls the temperatures of the second TEC plate (52) and the third TEC plate (53) to be consistent; the first TEC plate (51) is arranged directly below the π phase shift point of the distributed feedback fiber laser (4), corresponding to the highest point of the internal thermal field when the distributed feedback fiber laser (4) emits laser light, and the first TEC plate (51) is set to the lowest temperature.

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