High-efficiency deep red fiber laser and method for obtaining tunable laser

Abstract

The application relates to a high-efficiency deep red light fiber laser and a method for obtaining tunable laser, which comprises a blue light pump source, a dichroic mirror, a coupling aspheric lens, a gain fiber and a matching fiber arranged in sequence along a horizontal direction; a plane blazed grating is arranged on one side of the dichroic mirror in a Littrow structure to form a tunable laser resonant cavity for tuning laser; the blue light pump source emits laser which passes through the dichroic mirror and is coupled into the gain fiber by the coupling aspheric lens; the gain fiber and the matching fiber are connected at the end by a ceramic sleeve; the ceramic sleeve is internally provided with a fiber end face coating mirror, the fiber end face coating mirror is arranged between the connecting end of the gain fiber and the matching fiber; a free-running laser resonant cavity is formed between the fiber end face coating mirror and the fiber end face; the gain fiber is a single-clad fluorozirconate glass fiber, and the fiber end face coating mirror is a deep red light fiber end face coating mirror.

Description

Technical Field

[0001] This application relates to the technical field of deep-red fiber lasers, and more particularly to a high-efficiency deep-red fiber laser and a method for obtaining tunable laser light. Background Technology

[0002] 750nm deep-red lasers have broad application prospects in fields such as biomedicine, radar detection, and multiphoton microscopy. Ti:sapphire lasers are commonly used solid-state lasers in the deep-red band; however, their large size and high cost limit their widespread application in scientific research and industrial manufacturing. Fiber lasers, especially LD-pumped fiber lasers, are a new type of high-performance laser with advantages such as low cost, simple structure, and ease of integration. Developing LD-pumped fiber lasers in the deep-red band has profound significance for scientific research.

[0003] With the addition of Ho 3+ In-depth research on optical fibers has revealed the presence of Ho-doped fibers. 3+ Fluorozirconate glass fibers hold great potential for generating deep red lasers. As early as 1990, J.Y. Allain et al. used a 647.1 nm krypton-ion laser to pump Ho-doped fibers. 3+ Fluorozirconate glass fiber achieved 750nm laser output; until 2018, we reported the first successful use of a 450nm blue LD as a pump source to obtain 750nm deep red laser, but due to the lower energy level of the laser... 5 The I7 level has a lifetime exceeding 10 ms, which is much longer than that of the higher levels. 5 F4 5 The S2 level has a lifetime of 0.3 ms, and the population inversion between the upper and lower energy levels is difficult, leading to laser self-termination. Therefore, the slant efficiency of this deep red laser is only 3.9%. To overcome this self-termination bottleneck, SHJi et al. recently used 640 nm and 532 nm solid-state lasers to pump Ho-doped lasers. 3+ Fluorozirconate glass optical fibers reduce excited-state absorption (ESA). 5 The I7 level particle population enables high-efficiency watt-level deep red lasers. However, the use of a solid-state laser pump source undoubtedly increases the cost of the deep red fiber laser and leads to drawbacks such as large size and system complexity. Summary of the Invention

[0004] To address the bottlenecks of population inversion between upper and lower laser energy levels and laser self-termination, while effectively reducing costs, this application provides a high-efficiency deep-red fiber laser and a method for obtaining tunable laser light. The technical solution adopted is as follows:

[0005] A high-efficiency deep red fiber laser includes a blue pump source, a dichroic mirror, a coupling aspherical lens, a gain fiber, and a matching fiber arranged in a horizontal sequence; a planar blazed grating is placed on one side of the dichroic mirror in a Littrow structure to form a tuned laser resonant cavity for laser tuning.

[0006] The blue light pump source emits laser light, which passes through a dichroic mirror and is coupled into the gain fiber by a coupling aspherical lens; the gain fiber and the matching fiber are connected at their endpoints through a ceramic sleeve.

[0007] The ceramic sleeve contains a fiber end face coating mirror, which is placed between the connection end of the gain fiber and the matching fiber; the fiber end face coating mirror and the fiber end face form a free-running laser resonant cavity.

[0008] The gain fiber is a single-clad fluorozirconate glass fiber, and the fiber end-face coating mirror is a deep red fiber end-face coating mirror.

[0009] Optionally, the gain fiber is doped with rare earth ions.

[0010] Optionally, the rare earth ions doped in the gain fiber are holmium (Ho). 3+ The doping concentration is 1000ppm and the length is 1.0m.

[0011] Optionally, the blue light pump source is a blue light LD with a wavelength of 442±1nm.

[0012] Optionally, the deep red fiber end face coated mirror has a deep red light reflectivity greater than 99%.

[0013] Optionally, the dichroic mirror has high transmittance in the 400-700nm wavelength band and high reflectivity in the 700-800nm ​​wavelength band.

[0014] The dichroic mirror has a transmittance of more than 95% in the 400-700nm wavelength band and a reflectance of more than 99% in the 700-800nm ​​wavelength band.

[0015] Optionally, the planar blazed grating has a blazed wavelength of 750 nm and a blazed angle of 26°44′; the planar blazed grating has a reflectivity of more than 70% for deep red light at 750 nm.

[0016] A method for obtaining tunable laser light, using the deep red fiber laser described in any one of the above-mentioned methods; comprising the following steps:

[0017] Step 1: Turn on the blue light pump source, and after the emitted laser is transmitted through the dichroic mirror, it is coupled into the gain fiber by the coupling aspherical lens;

[0018] Step 2: The gain fiber is used to generate deep red light gain amplification under the combined action of ground state absorption and excited state absorption. Then, it enters the freely operating laser resonator to achieve population inversion and generate high-efficiency deep red laser reverse output.

[0019] Step 3: The deep red laser light output from the gain fiber is reflected by the dichroic mirror onto the planar blazed grating placed in a Littrow structure.

[0020] Step 4: Horizontally rotate the planar blazed grating to tune the reflected deep red laser and output the deep red laser through zero-order diffraction.

[0021] Optionally, the deep red fiber laser outputs deep red light in the range of 749.5–752.1 nm, which is tunable within the range with an accuracy of 0.1 nm.

[0022] Optionally, the deep red fiber laser output by the deep red laser can achieve a slope efficiency of up to 50.3%.

[0023] In summary, this application has the following beneficial effects:

[0024] 1. This invention employs a low-cost, simple 442±1nm blue LD pump source, reducing absorption in the 442nm excited state. 5 The particle population distribution of the I7 level effectively solves the bottleneck of the difficulty in reversing the particle population between the upper and lower energy levels of the laser and the phenomenon of laser self-termination. It realizes a high-efficiency deep red 750.6nm free-running laser with a slope efficiency of 50.3%, and at the same time, it uses a planar blazed grating to achieve high-precision tuning of 0.1nm in the range of 749.5-752.1nm.

[0025] 2. This invention ingeniously solves the problem of Ho doping through the study of a pumping mechanism. 3+ The self-terminating output bottleneck of deep red laser using fluorozirconium glass fiber has been overcome; high-efficiency continuous light output of deep red laser has been achieved, and at the same time, 750nm tunable laser output with blue LD pumping has been realized with a compact structure and low cost, solving the shortcomings of the past Ti:sapphire deep red continuous lasers that were too large and too expensive. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the fiber laser in this embodiment;

[0027] Figure 2 This is a laser energy level diagram of the fiber laser in this embodiment;

[0028] Figure 3 This is the power sloping efficiency diagram of the fiber laser in this embodiment (the upper left corner is the spectrum of the freely rotating deep red laser);

[0029] Figure 4 This is the tunable wavelength spectrum of the fiber laser in this embodiment.

[0030] Explanation of reference numerals in the attached diagram: 1. Blue light pump source; 2. Dichroic mirror; 3. Coupled aspherical lens; 4. Gain fiber ceramic ferrule; 5. Gain fiber; 6. Ceramic sleeve; 7. Fiber end face coating mirror; 8. Matching fiber ceramic ferrule; 9. Matching fiber; 10. Planar blazed grating. Detailed Implementation

[0031] The following is in conjunction with the appendix Figure 1 -4 provides further details regarding this application.

[0032] This application discloses a high-efficiency deep red fiber laser, including a blue pump source 1, a dichroic mirror 2, a coupling aspherical lens 3, a gain fiber 5, and a matching fiber 9 arranged horizontally in sequence; a planar blazed grating 10 is placed on one side of the dichroic mirror 2 in a Littrow structure.

[0033] The gain fiber 5 is a single-clad Ho-doped fiber. 3+ The optical fiber is a fluorozirconate glass fiber with gain fiber ceramic ferrules 4 at both ends. The gain fiber 5 and the matching fiber 9 are connected at their endpoints through a ceramic sleeve 6. A matching fiber ceramic ferrule 8 is provided at the connection section of the matching fiber 9, and an optical fiber end face coating mirror 7 is provided on the end face of the matching fiber ceramic ferrule 8 and contained in the ceramic sleeve 6, located between the connection ends of the gain fiber 5 and the matching fiber 9.

[0034] The fiber end face coating mirror 7 is located on the end face of the matching fiber ceramic ferrule 8, and is connected to the gain fiber ceramic ferrule 4 through the ceramic sleeve 6 to form a free-running laser resonant cavity; the dichroic mirror 2 and the planar blazed grating 10 placed in a Littrow structure form a tuned laser resonant cavity for tuning the laser.

[0035] The blue light pump source 1 provided in this application is a blue light LD with a wavelength of 442±1nm, and the gain fiber 5 is doped with rare earth ions holmium (Ho). 3+ The doping concentration is 1000ppm and the length is 1.0m.

[0036] The fiber end face coating mirror 7 provided in this application is a deep red fiber end face coating mirror 7, and the deep red fiber end face coating mirror 7 has a deep red light reflectivity greater than 99%.

[0037] The dichroic mirror 2 provided in this application has high transmittance in the 400-700nm wavelength band and high reflectivity in the 700-800nm ​​wavelength band; the dichroic mirror 2 has a transmittance of more than 95% in the 400-700nm wavelength band and a reflectivity of more than 99% in the 700-800nm ​​wavelength band.

[0038] The planar blazed grating 10 provided in this application has a blazed wavelength of 750nm and a blazed angle of 26°44′; the planar blazed grating 10 has a reflectivity of more than 70% for deep red light at 750nm.

[0039] like Figure 1 The laser path of the deep red fiber laser provided in this application is as follows: the laser emitted from the blue pump source 1 passes through the dichroic mirror 2, and is directly coupled into the core of the gain fiber 5 via the coupling aspherical lens 3, utilizing Ho-doped laser light. 3+ Fluorozirconate glass fiber, under the combined effect of ground state absorption and excited state absorption, generates deep red light gain amplification. The deep red light is generated by a free-running laser resonator formed by the high reflectivity deep red light band fiber end face coated mirror 7 and the fiber end face Fresnel reflection. The reflected output is reflected by dichroic mirror 2 and then onto a planar blazed grating 10 placed in a Littrow structure. By horizontally rotating the planar blazed grating 10, the generated deep red light laser can be tuned, realizing the tuning of deep red light while simultaneously tuning the laser output from the zero-order diffraction of the blazed grating.

[0040] like Figure 2 Single-layer Ho doping 3+ The energy level changes in the fluorozirconate glass fiber are as follows: 442nm continuous laser will... 5 The number of particles at level 11 in I8 is pumped to the ground state by absorption 15. 5 F4 5 S2 energy level 13, is 5 F4 5 The S2 energy level 13 accumulates the particle number; simultaneously, a 442nm continuous laser beam absorbs the particle number from the excited state 16. 5 I7 level 12 pump pump to 3 H6 energy level 14, 3 The number of particles in the H6 energy level 14 then increases through nonradiative transition 17 to... 5 F4 5 S2 energy level 13, this process not only reduces 5 The particle population at level 12 of I7 is, and is 5 F4 5 The S2 energy level 13 accumulates a number of particles, thereby achieving population inversion and generating a deep red laser 18.

[0041] A method for obtaining high-efficiency, tunable deep-red laser light using a deep-red fiber laser includes the following steps:

[0042] Step 1: Turn on the blue light pump source 1 and emit a 442nm pump laser. After being transmitted through the dichroic mirror 2, the laser is coupled into the single-clad Ho-doped laser by the coupling aspherical lens 3.3+ In the gain fiber 5 made of fluorozirconium glass;

[0043] Step 2: The gain fiber 5 is used to form a deep red light gain amplification under the combined action of ground state absorption and excited state absorption. Then, it enters the free-running laser resonator to realize population inversion and generate a high-efficiency deep red laser reverse output.

[0044] Step 3: The deep red laser light output from the gain fiber 5 is reflected by the dichroic mirror 2 to output a high-efficiency, free-moving deep red laser light, which is then reflected by the dichroic mirror 2 onto the planar blazed grating 10 placed in a Littrow structure.

[0045] Step 4: Horizontally rotate the planar blazed grating 10 to tune the reflected deep red laser and output deep red light through zero-order diffraction. At the same time, a high-precision (0.1nm) deep red laser with a tuning range of 749.5-752.1nm can be observed.

[0046] like Figure 3 The output power of the free-running deep red laser obtained from the above steps varies with the pump power, and the slope efficiency is 50.3%. The center wavelength is 750.6 nm, which can be obtained from the free-running deep red laser spectrum.

[0047] like Figure 4 The deep red laser tuning wavelength obtained from the above steps enables high-precision (0.1nm) tunable deep red laser output in the 749.5-752.1nm band.

[0048] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A high-efficiency deep-red fiber laser, characterized in that: It includes a blue light pump source, a dichroic mirror, a coupling aspherical lens, a gain fiber, and a matching fiber arranged in sequence along a horizontal plane; a planar blazed grating is placed on one side of the dichroic mirror in a Littrow structure to form a tuned laser resonator for tuning the laser. The blue light pump source emits laser light, which passes through a dichroic mirror and is coupled into the gain fiber by a coupling aspherical lens; the gain fiber and the matching fiber are connected at their endpoints through a ceramic sleeve. The ceramic sleeve contains a fiber end face coating mirror, which is placed between the connection end of the gain fiber and the matching fiber; the fiber end face coating mirror and the fiber end face form a free-running laser resonant cavity. The gain fiber is a single-clad fluorozirconate glass fiber, and the fiber end face coating mirror is a deep red fiber end face coating mirror. The gain fiber is doped with rare earth ions; the rare earth ions doped in the gain fiber are holmium (Ho). 3+ Its doping concentration is 1000ppm and its length is 1.0m.

2. The high-efficiency deep-red fiber laser according to claim 1, characterized in that: The blue light pump source is a blue light LD with a wavelength of 442±1nm.

3. A high-efficiency deep-red fiber laser according to claim 1, characterized in that: The deep red fiber end face coated mirror has a deep red light reflectivity of greater than 99%.

4. A high-efficiency deep-red fiber laser according to claim 1, characterized in that: The dichroic mirror has high transmittance in the 400-700nm wavelength range and high reflectivity in the 700-800nm ​​wavelength range; The dichroic mirror has a transmittance of more than 95% in the 400-700nm wavelength band and a reflectance of more than 99% in the 700-800nm ​​wavelength band.

5. A high-efficiency deep-red fiber laser according to claim 1, characterized in that: The planar blazed grating has a blazed wavelength of 750 nm and a blazed angle of 26°44′; the planar blazed grating has a reflectivity of more than 70% for deep red light at 750 nm.

6. A method for obtaining tunable laser light, characterized in that: Using the high-efficiency deep-red fiber laser according to any one of claims 1-5; comprising the following steps: Step 1: Turn on the blue light pump source, and after the emitted laser is transmitted through the dichroic mirror, it is coupled into the gain fiber by the coupling aspherical lens; Step 2: The gain fiber is used to generate deep red light gain amplification under the combined action of ground state absorption and excited state absorption. Then, it enters the freely operating laser resonator to achieve population inversion and generate high-efficiency deep red laser reverse output. Step 3: The deep red laser light output from the gain fiber is reflected by the dichroic mirror onto the planar blazed grating placed in a Littrow structure. Step 4: Horizontally rotate the planar blazed grating to tune the reflected deep red laser and output the deep red laser through zero-order diffraction.

7. The method for obtaining tunable laser light according to claim 6, characterized in that: The deep red fiber laser outputs deep red light in the range of 749.5-752.1 nm, which is tunable within this range with an accuracy of 0.1 nm.

8. The method for obtaining tunable laser light according to claim 6, characterized in that: The deep red fiber laser output has a slope efficiency of up to 50.3%.

Images