A mid-infrared fiber laser system

Abstract

The application relates to the field of middle infrared laser, and particularly provides a middle infrared fiber laser system, which comprises a semiconductor pumping source, a rare earth ion doped middle infrared fiber and a middle infrared laser outlet; the semiconductor pumping source comprises a semiconductor surface emitting laser pumping source chip with double light emitting areas; the pumping source chip comprises, from bottom to top, an N-type electrode layer, a substrate layer, an N-type DBR reflector, a lower limiting layer, an active layer, an upper limiting layer, an oxidation layer, a P-type cover layer, a P-type electrode layer and a P-type dielectric film reflector; the P-type electrode layer is provided with two light emitting holes; and the oxidation layer is provided with an oxidation hole; the middle infrared laser outlet comprises, from bottom to top, a fiber cladding layer, a fiber core layer and an etched second-order grating structure; and the middle infrared fiber comprises a fiber cladding layer and a fiber core layer. The two light emitting areas in the scheme can be directly aligned with two end faces of the middle infrared fiber respectively, the coupling efficiency can be improved, the volume of the system can be reduced, and the middle infrared fiber can be prevented from being damaged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mid-infrared laser, and particularly relates to a mid-infrared fiber laser system. BACKGROUND

[0002] 3-5 μm band mid-infrared laser has a wide application prospect and market demand in the fields of national defense safety, remote sensing, space communication, atmospheric monitoring, biochemical sensing, spectral analysis and the like due to the minimum atmospheric transmission window corresponding to the decay and covering many molecular absorption peaks. At present, in the field of 3-5 μm band mid-infrared laser research, semiconductor quantum cascade laser, transition metal doped chalcogenide (such as Fe2+: ZnSe) solid laser, optical parametric oscillator (OPO), supercontinuum light source and fiber laser are the research and development focuses.

[0003] Among them, 1) the quantum cascade laser has the characteristics of small volume, high photoelectric conversion efficiency and continuous operation, but the quantum cascade laser needs a complex growth process, and the heat dissipation of the device also limits the output power of the single tube device (<1 W); 2) the transition metal doped chalcogenide solid laser has the disadvantage that the laser output efficiency is seriously reduced as the temperature rises, which is difficult to meet the demand of high-power output at room temperature; 3) the optical parametric oscillator OPO can realize mid-infrared laser output by high-power laser pumping a nonlinear crystal, but the beam quality is poor (M2 ~ dozens), and the structure of the laser is complex and the heat management is difficult; 4) the supercontinuum light source has an extremely wide spectral bandwidth, so that the energy density of the mid-infrared laser source in a single band range is too low, and since a femtosecond laser is used as a pumping source, it is difficult to realize high-power continuous laser output of the mid-infrared laser; 5) the optical fiber has excellent heat dissipation performance due to the large surface / volume ratio of the optical fiber, and the excellent double-clad waveguide mechanism enables the optical fiber laser to have large power pumping capacity and ideal beam quality, the inherent fully enclosed flexible light path of the optical fiber enables it to adapt to harsh environments and has extremely high flexibility and stability, and the optical fiber laser also has the advantages of maintenance-free, long service life, small size, light weight, high energy conversion efficiency and the like.

[0004] As can be seen from the above, compared with other mid-infrared lasers, the optical fiber laser has incomparable technical superiority and can be applied to many fields. The basic structure of the existing mid-infrared all-fiber optical fiber laser system is as shown in Figure 1 Taking 3.9 um mid-infrared fiber laser as an example, a 890 nm semiconductor pump source 1 is used to pump a mid-infrared fiber 2 doped with Ho3+ ions, and a fiber grating (FBG) is written at both ends of the mid-infrared fiber 2 to form a mirror to support laser oscillation, and the laser is emitted at a mid-infrared laser emission port 3. The existing technology mainly has the following problems:

[0005] 1. Semiconductor pump source 1 is a side-emitting semiconductor, which requires independent butterfly packaging and cooling, increasing the size and power consumption of the entire system;

[0006] 2. Currently, the fabrication technology of mid-infrared fiber gratings (FBGs) is only in the preliminary research stage. The fabrication process of fiber gratings is prone to introducing large fiber damage, which affects the power characteristics and reliability of the system.

[0007] In summary, designing a mid-infrared fiber laser system that can reduce the size and power consumption of the laser system while avoiding fiber damage is an urgent problem to be solved. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a mid-infrared fiber laser system, comprising a semiconductor surface-emitting laser pump source chip with dual emission regions, a rare-earth ion-doped mid-infrared fiber, and a mid-infrared laser emission port formed by etching a second-order grating. This system can reduce system size and power consumption, ensure system power stability, and avoid fiber damage.

[0009] To achieve the above objectives, the present invention proposes the following technical solution: a mid-infrared fiber laser system, comprising a semiconductor pump source, a mid-infrared fiber, and a mid-infrared laser emission port formed by etching a second-order grating on the mid-infrared fiber; the semiconductor pump source includes a semiconductor surface-emitting laser pump source chip with dual emission regions, and the mid-infrared fiber is doped with rare earth ions; the two emission regions of the semiconductor pump source are respectively aligned with the two end faces of the mid-infrared fiber, and the pump laser emitted from the two emission regions is directly input into the mid-infrared fiber to excite the gain medium in the fiber to generate mid-infrared laser; the mid-infrared laser is vertically coupled and emitted at the mid-infrared laser emission port through a second-order grating.

[0010] Preferably, the pump source chip comprises, from bottom to top, an N-type electrode layer, a substrate layer, an N-type DBR mirror, a lower confinement layer, an active layer, an upper confinement layer, an oxide layer, a P-type capping layer, and a P-type electrode layer; the P-type electrode layer is provided with a P-type dielectric film mirror, and the P-type electrode layer includes two light-emitting holes located at the lower end of the P-type dielectric film mirror, the two light-emitting holes forming the light-emitting ports of each light-emitting region in the dual-emitting region of the laser pump source chip; the oxide layer includes oxide holes.

[0011] Preferably, the P-type dielectric film reflector is composed of multiple layers of different dielectric film materials. The thickness of each dielectric film material is set according to the wavelength range of the pump laser and the mid-infrared laser so that the P-type dielectric film reflector has high reflectivity in both the pump laser band and the mid-infrared laser band. The thickness of each dielectric film material in the P-type dielectric film reflector ranges from 0.1 to 1 micrometer.

[0012] Preferably, the middle infrared laser exit port comprises, from bottom to top, a fiber cladding layer, a fiber core layer and an etched second-order grating structure, the fiber cladding layer has a diameter ranging from 20 to 500 microns, and the fiber core layer has a diameter ranging from 1 to 100 microns; the grating period of the second-order grating structure is half of the wavelength of the middle infrared laser / the refractive index of the fiber cladding layer.

[0013] Preferably, the middle infrared fiber comprises a fiber cladding layer and a fiber core layer, the middle infrared fiber is a fluoride fiber, a fluorotellurite fiber or a chalcogenide fiber; the rare earth ions doped in the middle infrared fiber include Er 3+ , Dy 3+ , Ho 3+ ; the total length of the middle infrared fiber is 0.5-10 meters.

[0014] Preferably, in the process of preparing the P-type metal electrode, a light hole is prepared by a lift-off process, the diameter of the light hole ranges from 1 to 100 microns; the length of a single light emitting region ranges from 250 to 500 microns.

[0015] Preferably, the substrate layer is an N-type GaAs material; the material of the N-type DBR mirror is a periodically grown AlGaAs material, each set of the material of the N-type DBR mirror comprises two AlGaAs layers with different Al contents, the Al content of each AlGaAs layer ranges from 0.05 to 0.95, the thickness of each AlGaAs layer is a quarter of the wavelength of the emitted light / the refractive index of the cover layer material, the period logarithm ranges from 10 pairs to 40 pairs, inclusive, the total thickness ranges from 2 microns to 5 microns, inclusive; the dopant in each AlGaAs layer is Si, and the doping concentration is 1E18-8E18 / cm3; the light emitted by the active layer is reflected back into the pump source chip through the N-type DBR mirror and forms light oscillation together with the P-type dielectric film mirror.

[0016] Preferably, the material of the lower confinement layer is AlGaAs, the Al content ranges from 0 to 0.9, the thickness ranges from 1 to 1000 nanometers, the dopant is Si, and the doping concentration is 1E15-8E18 / cm3; the active layer is not actively doped, the active layer has a barrier / quantum well / barrier structure, the material of the active layer is AlGaAsP / InAlGaAs / AlGaAsP, the In content of the active layer ranges from 0 to 0.5, the Al content ranges from 0 to 0.5, the P content ranges from 0 to 0.2, the barrier thickness ranges from 1 nanometer to 200 nanometers, the quantum well thickness ranges from 1 nanometer to 20 nanometers, and the light emission wavelength ranges from 700 nanometers to 1200 nanometers; the material of the upper confinement layer is AlGaAs, the Al content ranges from 0 to 0.9, the thickness ranges from 1 to 1000 nanometers, the dopant is C, and the doping concentration is 1E15-8E18 / cm3; the lower confinement layer, the active layer and the upper confinement layer form an active cavity of the surface emitting laser, and the thickness of the active cavity is the wavelength of the emitted light / the average refractive index of the active cavity.

[0017] Preferably, the material of the oxidation layer is AlGaAs, the Al component content in the oxidation layer is 0.98, the thickness ranges from 5 nanometers to 30 nanometers, inclusive; the oxidation layer is made by a wet oxidation process, part of the AlGaAs is oxidized into an insulating material to form the oxidation layer, and the unoxidized AlGaAs forms the oxidation hole; the diameter of the oxidation hole ranges from 1 to 100 microns, inclusive.

[0018] Preferably, the material of the P-type cap layer is GaAs, the thickness of the P-type cap layer ranges from 100 nanometers to 1 micron, inclusive, the dopant is C, and the doping concentration is 1E18-1E19 / cm3; the P-type cap layer forms an ohmic contact with the P-type electrode layer and reduces the resistance; the thickness of the P-type electrode layer and the N-type electrode layer is 200 nanometers-500 nanometers, and the material of the P-type electrode layer and the N-type electrode layer is an alloy material including titanium, platinum, gold, nickel, and germanium.

[0019] The present application has the following advantages:

[0020] 1. The present application adopts a surface emitting laser structure with double emitting areas, two emitting areas are respectively aligned with two end faces of a rare earth doped mid-infrared optical fiber, the pump laser emitted by the two emitting areas of the surface emitting semiconductor laser is directly input into the mid-infrared optical fiber to excite the gain medium in the optical fiber to generate mid-infrared laser; the spot emitted by the surface emitting laser is circular, which can be directly coupled into the optical fiber, greatly improving the coupling efficiency, and the size of the surface emitting laser is similar to that of the optical fiber, so that the pump source chip and the optical fiber end face can be directly coupled and packaged, greatly reducing the volume of the system.

[0021] 2. The present application includes a P-type dielectric film mirror, firstly, the P-type dielectric film mirror serves as the upper mirror of the semiconductor surface emitting laser pump source chip, which can reflect the pump laser back into the laser cavity to form laser oscillation together with the N-type DBR mirror, and the pump laser is emitted from the surface of the P-type dielectric film mirror through the light emitting hole; secondly, the P-type dielectric film mirror serves as the two mirrors of the mid-infrared fiber laser, which can form optical oscillation in the optical fiber; further, the P-type dielectric film mirror provides sufficient reflectivity for the surface emitting semiconductor pump source structure to reach the lasing threshold condition, so as to emit pump laser, and also provides sufficient reflectivity for the mid-infrared excitation light propagating in the fiber core to form stable oscillation between the two end faces of the optical fiber and finally reach the lasing threshold condition to form mid-infrared laser.

[0022] 3. The second-order grating structure is etched in the mid-infrared laser exit, so that the mid-infrared laser can be emitted through vertical coupling formed by the second-order grating structure at any position of the optical fiber, which can improve the coupling efficiency and ensure the reliability of the system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a fiber laser system in the background technology.

[0024] Figure 2 This is a schematic diagram of the mid-infrared fiber laser system provided in an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of the structure of the pump source chip in the semiconductor pump source provided in the embodiment of the present invention.

[0026] Figure 4 This is a schematic diagram of the structure of the mid-infrared laser emission port provided in an embodiment of the present invention.

[0027] Figure 5 This is a schematic diagram of the light field distribution of the pump laser and the mid-infrared laser in the mid-infrared fiber provided in the embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram of the reflection spectrum of the P-type dielectric film reflector provided in an embodiment of the present invention.

[0029] Figure reference numerals: 1. Semiconductor pump source; 2. Mid-infrared fiber; 3. Mid-infrared laser emission port; 4. N-type electrode layer; 5. Substrate layer; 6. N-type DBR mirror; 7. Lower confinement layer; 8. Active layer; 9. Upper confinement layer; 10. Oxide layer; 11. P-type capping layer; 12. P-type electrode layer; 13. P-type dielectric film mirror; 14. Oxide hole; 15. Light emission hole; 16. Fiber cladding; 17. Fiber core; 18. Second-order grating structure. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with the appendix. Figures 1-6 The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and do not constitute a limitation thereof.

[0031] A mid-infrared fiber laser system includes a semiconductor pump source 1, a mid-infrared fiber 2, and a mid-infrared laser emission port 3 formed by etching a second-order grating on the mid-infrared fiber 2; as shown Figure 3 As shown, the semiconductor pump source 1 includes a semiconductor surface-emitting laser pump source chip with dual emission regions, the dual emission regions being respectively Figure 3 The first emitting region shown at Q1 and the second emitting region shown at Q2 are two emitting regions of the semiconductor pump source 1, which are respectively aligned with the two end faces of the mid-infrared optical fiber 2. The pump laser emitted from the two emitting regions is directly input into the mid-infrared optical fiber 2 to excite the gain medium in the fiber to generate mid-infrared laser. The mid-infrared laser is vertically coupled and emitted at the mid-infrared laser emission port 3 through a second-order grating.

[0032] As Figure 3 shown, the pump source chip includes, from bottom to top, an N-type electrode layer 4, a substrate layer 5, an N-type DBR mirror 6, a lower confinement layer 7, an active layer 8, an upper confinement layer 9, an oxidation layer 10, a P-type cover layer 11, and a P-type electrode layer 12; the P-type electrode layer 12 is provided with a P-type dielectric film mirror 13, and the P-type electrode layer 12 includes two light-emitting holes 15 located at the lower end of the P-type dielectric film mirror 13, which form light-emitting openings of each light-emitting area in the dual light-emitting area of the laser pump source chip; the oxidation layer 10 includes an oxidation hole 14; in the process of preparing the P-type metal electrode, the light-emitting hole 15 is prepared by the lift-off process, and the diameter of the light-emitting hole 15 ranges from 1 to 100 microns; the length of a single light-emitting area ranges from 250 to 500 microns; the total length of the laser device is 500-1000 microns, and the width is half of the length.

[0033] The P-type dielectric film mirror 13 is composed of multiple layers of different dielectric film materials, including but not limited to SiO2, TiO2, Si4N3, Al2O3, and Ta2O5. The thickness of each layer of dielectric film material is set according to the wavelength range of the pump laser and the mid-infrared laser. By designing specific dielectric film materials and their thicknesses, the P-type dielectric film mirror 13 has high reflection characteristics in the pump laser wavelength range and the mid-infrared laser wavelength range. The thickness of each layer of dielectric film material in the P-type dielectric film mirror 13 ranges from 0.1 to 1 micron.

[0034] The substrate layer 5 is an N-type GaAs material; the material of the N-type DBR mirror 6 is a periodically grown AlGaAs material, and each set of N-type DBR mirror 6 material contains two layers of AlGaAs with different Al contents, the Al content of each layer of AlGaAs material is 0.05-0.95, the thickness is the quarter of the refractive index of the cover layer material, the period logarithm ranges from 10 pairs to 40 pairs, including the end point value, the total thickness ranges from 2 microns to 5 microns, including the end point value; the dopant in each layer of AlGaAs material is Si, and the doping concentration is 1E18-8E18 / cm3; the light emitted by the active layer 8 is reflected back to the inside of the pump source chip by the N-type DBR mirror 6 and forms an optical oscillation together with the P-type dielectric film mirror 13.

[0035] The material of the lower confinement layer 7 is AlGaAs, the Al component content is 0-0.9, the thickness ranges from 1-1000 nanometers, the dopant is Si, and the doping concentration is 1E15-8E18 / cm3; the active layer 8 is not actively doped, the active layer 8 is a barrier / quantum well / barrier structure, the material of the active layer 8 is AlGaAsP / InAlGaAs / AlGaAsP, the In component content of the active layer 8 is 0-0.5, the Al component content is 0-0.5, the P component content is 0-0.2, the barrier thickness is 1 nanometer-200 nanometers, the quantum well thickness is 1 nanometer-20 nanometers, and the light-emitting wavelength band is 700 nanometers-1200 nanometers; the material of the upper confinement layer 9 is AlGaAs, the Al component content is 0-0.9, the thickness ranges from 1-1000 nanometers, the dopant is C, and the doping concentration is 1E15-8E18 / cm3; the lower confinement layer 7, the active layer 8, and the upper confinement layer 9 form an active cavity of the surface-emitting laser, and the thickness of the active cavity is the light-emitting wavelength / the average refractive index of the active cavity.

[0036] The material of the oxidation layer 10 is AlGaAs, the Al component content in the oxidation layer 10 is 0.98, the thickness ranges from 5 nanometers-30 nanometers, and the end point value is included; the oxidation layer 10 is formed by a wet oxidation process, part of the AlGaAs is oxidized into an insulating material to form the oxidation layer 10, and the unoxidized AlGaAs forms the oxidation hole 14; the diameter of the oxidation hole 14 ranges from 1-100 micrometers, and the end point value is included; in this way, the current injected by the P-type electrode is limited to the center of the active layer of the surface-emitting laser.

[0037] The material of the P-type cap layer 11 is GaAs, the thickness of the P-type cap layer 11 ranges from 100 nanometers to 1 micrometer, the end point value is included, the dopant is C, and the doping concentration is 1E18-1E19 / cm3; the P-type cap layer 11 forms an ohmic contact with the P-type electrode layer 12 and reduces the resistance; the thickness of the P-type electrode layer 12 and the N-type electrode layer 4 is 200 nanometers-500 nanometers, and the material of the P-type electrode layer 12 and the N-type electrode layer 4 is an alloy material including titanium, platinum, gold, nickel, and germanium.

[0038] The middle infrared fiber 2 is doped with rare earth ions, and the rare earth ions include but are not limited to Er3+, Dy3+, and Ho3+, according to the type of the doped rare earth ions, the corresponding pump laser wavelength band mainly distributes in 808-980 nanometers, and the middle infrared laser wavelength band that can be emitted covers 3-4 micrometers; the middle infrared fiber 2 includes a fiber cladding layer 16 and a fiber core layer 17, and the middle infrared fiber 2 is a fluoride fiber, a fluorotellurite fiber, or a chalcogenide fiber; the total length of the middle infrared fiber 2 is 0.5-10 meters.

[0039] As Figure 4As shown, the middle infrared laser exit port 3 includes, from bottom to top, a fiber cladding layer 16, a fiber core layer 17, and an etched second-order grating structure 18. The diameter of the fiber cladding layer 16 ranges from 20 to 500 microns, and the diameter of the fiber core layer 17 ranges from 1 to 100 microns. The grating period of the second-order grating structure 18 is: half of the wavelength of the middle infrared laser / the refractive index of the fiber cladding layer 16. For example, the grating period of the second-order grating structure 18 is: 1.5 microns / 1.5 = 1 micron. Figure 4 As shown, the middle infrared laser oscillates back and forth in the fiber. At the second-order grating structure 18, part of the middle infrared laser is vertically coupled to generate middle infrared laser output.

[0040] Figure 5 The schematic diagram of the light field distribution of the pump laser and the middle infrared laser in the middle infrared fiber for simulation calculation is shown in FIG. 6. As shown in the figure, the middle infrared fiber 2 can well confine the pump laser and the middle infrared laser in the fiber core layer, thereby ensuring the pump efficiency and low loss of the middle infrared laser.

[0041] Figure 6 The reflection spectrum of the P-type dielectric film mirror 13 structure in a specific design of the present application is shown in FIG. 7. The design is for a middle infrared laser of 3.9 microns, and the corresponding pump laser wavelength is 890 nanometers. Figure 6 The upper graph in FIG. 7 is the full-band reflection spectrum from 500 to 5000 nanometers, and the lower two graphs are the local reflection spectrum of the pump laser and the middle infrared laser band. As shown in the figure, the P-type dielectric film mirror 13 in the present embodiment can simultaneously serve as a pump laser and middle infrared laser reflector.

[0042] The working principle of the middle infrared fiber laser system is as follows. First, the positive and negative electrodes of the semiconductor surface-emitting laser pump source chip are powered, and the chip generates laser oscillation under the electric excitation and emits from the light exit hole 15 on the upper surface of the chip. The emitted laser directly enters the middle infrared fiber 2 in contact with the upper surface of the semiconductor surface-emitting laser pump source chip. The middle infrared fiber 2 uses rare earth ion doping as the gain medium of the middle infrared laser, and emits middle infrared excitation light after absorbing the pump laser. The middle infrared light excited in the middle infrared fiber 2 propagates in the fiber. At the two end faces of the fiber, the middle infrared laser is reflected by the surface P-type dielectric film mirror 13 of the semiconductor surface-emitting laser pump source chip in direct contact with the fiber, forming optical oscillation amplification in the fiber, and finally forming middle infrared laser. The middle infrared laser is vertically coupled and emitted through the second-order grating structure 18 at the fiber exit port position.

[0043] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those skilled in the art can make changes, modifications, replacements, and variations to the above embodiments within the scope of the present application.

[0044] The above detailed description of the application is not intended to limit the scope of the application. Various other changes and modifications of the application can be made by those skilled in the art without departing from the scope of the application.

Claims

1. A mid-infrared fiber laser system, characterized in that, The semiconductor pump source (1), the mid-infrared fiber (2) and the mid-infrared laser exit (3) formed by etching a second-order grating on the mid-infrared fiber (2); the semiconductor pump source (1) comprises a semiconductor surface emitting laser pump source chip with double light emitting areas, and the mid-infrared fiber (2) is doped with rare earth ions; the two light emitting areas of the semiconductor pump source (1) are respectively aligned with the two end faces of the mid-infrared fiber (2), and the two end faces of the mid-infrared fiber (2) are respectively connected with the corresponding light emitting areas; the pump laser emitted by the two light emitting areas is directly input into the mid-infrared fiber (2) to excite the gain medium in the fiber to generate mid-infrared laser, and the mid-infrared laser is formed into vertical coupling emission at the mid-infrared laser exit (3) through a second-order grating; the mid-infrared laser exit (3) comprises, from bottom to top, a fiber cladding layer (16), a fiber core layer (17) and an etched second-order grating structure (18), and the grating period of the second-order grating structure (18) is half of the wavelength of the mid-infrared laser / the refractive index of the fiber cladding layer (16); The pump source chip comprises, from bottom to top, an N-type electrode layer (4), a substrate layer (5), an N-type DBR reflector (6), a lower confinement layer (7), an active layer (8), an upper confinement layer (9), an oxidation layer (10), a P-type cover layer (11) and a P-type electrode layer (12); two P-type dielectric film reflectors (13) are arranged on the P-type electrode layer (12) and located in the two light emitting areas respectively; the P-type dielectric film reflector (13) reflects the pump laser back into the laser cavity to form laser oscillation together with the N-type DBR reflector (6), and makes the pump laser emit from the surface of the P-type dielectric film reflector (13); the P-type dielectric film reflector (13) forms optical oscillation of the mid-infrared laser in the fiber and finally reaches the lasing threshold condition to form the mid-infrared laser.

2. The mid-infrared fiber laser system of claim 1, wherein, The P-type electrode layer (12) comprises two light emitting holes (15) located at the lower end of the P-type dielectric film reflector (13), and the two light emitting holes (15) form the light emitting port of each light emitting area in the double light emitting areas of the laser pump source chip; the oxidation layer (10) comprises an oxidation hole (14).

3. The mid-infrared fiber laser system of claim 2, wherein, The P-type dielectric film reflector (13) is composed of multiple different dielectric film materials, and the thickness of each layer of dielectric film material is set according to the wavelength range of the pump laser and the mid-infrared laser to make the P-type dielectric film reflector (13) have high reflection characteristics in the pump laser wavelength range and the mid-infrared laser wavelength range; the thickness of each layer of dielectric film material in the P-type dielectric film reflector (13) ranges from 0.1 to 1 microns.

4. The mid-infrared fiber laser system of claim 3, wherein, The diameter of the fiber cladding layer (16) ranges from 20 to 500 microns, and the diameter of the fiber core layer (17) ranges from 1 to 100 microns.

5. The mid-infrared fiber laser system of claim 4, wherein, The mid-infrared fiber (2) comprises a fiber cladding layer (16) and a fiber core layer (17), and the mid-infrared fiber (2) is a fluoride fiber, a fluorotellurite fiber or a sulfur-based fiber; the rare earth ions doped in the mid-infrared fiber (2) include Er3+, Dy3+ and Ho3+; the total length of the mid-infrared fiber (2) ranges from 0.5 to 10 meters.

6. The mid-infrared fiber laser system of claim 5, wherein, In the process of preparing the P-type metal electrode, a light hole (15) is prepared by a lift-off process, the diameter of the light hole (15) ranges from 1 to 100 microns, and the length of a single light emitting area ranges from 250 to 500 microns.

7. The mid-infrared fiber laser system of any of claims 2-6, wherein, The substrate layer (5) is an N-type GaAs material; the material of the N-type DBR reflector (6) is periodically grown AlGaAs material, each set of the material of the N-type DBR reflector (6) comprises two layers of AlGaAs with different Al contents, the Al content of each layer of AlGaAs material ranges from 0.05 to 0.95, the thickness is a quarter of the refractive index of the cover layer material of the emitted light wavelength, the period logarithm ranges from 10 pairs to 40 pairs, inclusive, the total thickness ranges from 2 microns to 5 microns, inclusive; the dopant in each layer of AlGaAs material is Si, and the doping concentration is 1E18-8E18 / cm3; the light emitted by the active layer (8) is reflected back into the pump source chip through the N-type DBR reflector (6) and forms an optical oscillation together with the P-type dielectric film reflector (13).

8. The mid-infrared fiber laser system of claim 7, wherein, The material of the lower confinement layer (7) is AlGaAs, the Al content ranges from 0 to 0.9, the thickness ranges from 1 to 1000 nanometers, the dopant is Si, and the doping concentration is 1E15-8E18 / cm3; the active layer (8) is not actively doped, the active layer (8) is a barrier / quantum well / barrier structure, the material of the active layer (8) is AlGaAsP / InAlGaAs / AlGaAsP, the In content of the active layer (8) ranges from 0 to 0.5, the Al content ranges from 0 to 0.5, the P content ranges from 0 to 0.2, the barrier thickness ranges from 1 nanometer to 200 nanometers, the quantum well thickness ranges from 1 nanometer to 20 nanometers, and the light emission wavelength ranges from 700 nanometers to 1200 nanometers; the material of the upper confinement layer (9) is AlGaAs, the Al content ranges from 0 to 0.9, the thickness ranges from 1 to 1000 nanometers, the dopant is C, and the doping concentration is 1E15-8E18 / cm3; the lower confinement layer (7), the active layer (8), and the upper confinement layer (9) form an active cavity of the surface emitting laser, and the thickness of the active cavity is the average refractive index of the active cavity.

9. The mid-infrared fiber laser system of claim 8, wherein, The material of the oxidation layer (10) is AlGaAs, the Al content in the oxidation layer (10) is 0.98, and the thickness ranges from 5 nanometers to 30 nanometers, inclusive; the oxidation layer (10) is made by a wet oxidation process, part of the AlGaAs is oxidized into an insulating material to form the oxidation layer (10), and the unoxidized AlGaAs forms an oxidation hole (14); the diameter of the oxidation hole (14) ranges from 1 to 100 microns, inclusive.

10. The mid-infrared fiber laser system of claim 9, wherein, The material of the P-type cap layer (11) is GaAs, the thickness of the P-type cap layer (11) ranges from 100 nm to 1 μm, inclusive, the dopant is C, and the doping concentration is 1E18-1E19 / cm3; an ohmic contact is formed between the P-type cap layer (11) and the P-type electrode layer (12) and the resistance is reduced; the thickness of the P-type electrode layer (12) and the N-type electrode layer (4) is both 200 nm-500 nm, and the material of the P-type electrode layer (12) and the N-type electrode layer (4) is an alloy material including titanium, platinum, gold, nickel, and germanium.

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