CN110581431B - Erbium-doped fluoride fiber laser and laser generation method - Google Patents

Erbium-doped fluoride fiber laser and laser generation method Download PDF

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CN110581431B
CN110581431B CN201910858129.9A CN201910858129A CN110581431B CN 110581431 B CN110581431 B CN 110581431B CN 201910858129 A CN201910858129 A CN 201910858129A CN 110581431 B CN110581431 B CN 110581431B
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laser
fiber
erbium
bragg grating
doped fluoride
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CN110581431A (en
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刘军
吴佳东
陈宇
邓志象
方志强
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Shenzhen University
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Shenzhen University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
    • H01S3/06716—Fibre compositions or doping with active elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/0675—Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06754—Fibre amplifiers
    • H01S3/06783—Amplifying coupler
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094049—Guiding of the pump light
    • H01S3/094053—Fibre coupled pump, e.g. delivering pump light using a fibre or a fibre bundle

Abstract

The invention provides an erbium-doped fluoride fiber laser and a laser generation method, comprising at least one pump laser, a beam combiner, a first fiber Bragg grating, a second fiber Bragg grating, a double-cladding erbium-doped fluoride fiber, a third fiber Bragg grating and AlF3An end cap. According to the laser, 1.6 mu m laser is constrained by the second optical resonant cavity formed by the first fiber Bragg grating and the third fiber Bragg grating and is finally excited state energy level of erbium ions4I13/2Absorption pumping to energy level4I9/2And then relax back to the energy level by multiphoton relaxation4I11/2Energy level of4I11/2Can be transited to energy level by pump light4I13/22.8 μm laser is generated, so that not only the 1.6 μm laser is recycled, but also the energy level is enabled4I13/2The particles are recycled, the self-termination effect of the 2.8-micron laser oscillation is reduced, and the energy utilization rate of the laser is greatly improved.

Description

Erbium-doped fluoride fiber laser and laser generation method
Technical Field
The invention belongs to the technical field of laser, and particularly relates to an erbium-doped fluoride fiber laser and a laser generation method.
Background
The fiber laser, as a novel laser, has the pure natural advantages of high conversion efficiency, good beam quality, compact structure, good portability, easy realization of commercialization and the like, and is always the focus of people. Among them, fluoride fiber lasers in the mid-infrared 2.8 μm band have attracted attention. With the continuous improvement of the process of the intermediate infrared fluoride optical fiber material, the output power of the obtained 2.8-micron-band laser is higher and higher, and the high-power 2.8-micron optical fiber laser is widely applied to aspects of regenerated material medical treatment, material processing, gas detection and the like, and becomes a hot field for research of researchers.
At present, Er is doped by a 976nm laser pump typical for 2.8 mu m wave band laser3+Fluoride fiber having energy level adjusted by erbium ion4I11/2Transition to energy level4I13/2Thus obtaining the product. But this solution is due to the fact that erbium ions are at the excitation level4I13/2Upper ion retention time (9.0ms) much greater than at higher energy levels4I11/2Reserve time (6.9ms) to result in energy levels4I11/2The number of erbium ions on the laser is reduced, and the laser energy level transition self-terminates due to insufficient particle inversion number; on the other hand the solution is usually accompanied by4I13/2→4I15/2The 1.6 μm band parasitic oscillation of the energy level transition is generated, so as to generate a byproduct 1.6 μm laser, which not only seriously affects the quantum efficiency of the laser (so that the theoretical quantum efficiency is limited to 35%), but also causes the laser to generate a large amount of extra heat and affects the stability of the laser.
Therefore, the prior art is subject to further improvement.
Disclosure of Invention
In view of the above-mentioned disadvantages in the prior art, the present invention is directed to an erbium-doped fluoride fiber laser and a laser generation method, which overcome the defect that the existing 2.8 μm erbium-doped fluoride laser has erbium ions at the excitation level4I13/2The lifetime of the upper energy level is far greater than that of the higher energy level4I11/2Resulting in self-termination of the laser energy level transition, and at the energy level4I13/2And4I15/2the 1.6 μm laser is generated, so that the efficiency of the fiber laser is reduced, the energy is not utilized, a large amount of heat is generated, and the defect of further improvement of the output power of the laser is limited.
A first embodiment disclosed in the present invention is an erbium-doped fluoride fiber laser, comprising at least one pump laser, a beam combiner, a first optical fiber, and a second optical fiberFiber Bragg grating, second fiber Bragg grating, double-clad erbium-doped fluoride fiber, third fiber Bragg grating and AlF3An end cap; wherein the content of the first and second substances,
the pump laser is used for generating pump light;
the second fiber Bragg grating and the AlF3An end cap forming a first optical resonant cavity, said double-clad erbium-doped fluoride fiber being located within said first optical resonant cavity;
the first fiber Bragg grating and the third fiber Bragg grating form a second optical resonant cavity, and the double-cladding erbium-doped fluoride fiber is positioned in the second optical resonant cavity;
and after being combined by the beam combiner, the pump light is coupled into the inner cladding and the fiber core of the double-cladding erbium-doped fluoride optical fiber, oscillates in the first optical resonant cavity and the second optical resonant cavity to form laser, and is converted into laser by the AlF3And (4) outputting by an end cap.
The erbium-doped fluoride fiber laser is characterized in that the wavelength of the pump light is 976 nm.
The reflectivity of the second fiber Bragg grating to 2.8 mu m laser is more than 99%, and the working bandwidth is less than 0.9 nm.
The reflectivity of the first fiber Bragg grating to 1.6 mu m laser is more than 99%, and the working bandwidth is less than 0.9 nm.
The reflectivity of the third fiber Bragg grating to the laser with the wavelength of 1.6 mu m is more than 99%, and the working bandwidth is less than 0.9 nm.
The erbium-doped fluoride fiber laser is characterized in that the working wavelength of the beam combiner is 976 nm.
The erbium-doped fluoride fiber laser is characterized in that the diameter of an inner cladding of the double-cladding erbium-doped fluoride fiber is 100-300 mu m, and the diameter of a fiber core of the double-cladding erbium-doped fluoride fiber is 10-30 mu m.
The erbium-doped fluoride fiber laser further comprises a cladding mode stripper;
the cladding mode stripper is positioned between the third fiber Bragg grating and the AlF3And between the end caps, for filtering out residual pump light.
The erbium-doped fluoride fiber laser comprises a double-clad erbium-doped fluoride fiber, wherein the erbium ion doping amount of the double-clad erbium-doped fluoride fiber is l% -3% in mole percentage, and the length of the double-clad erbium-doped fluoride fiber is 15-20 m.
A laser generation method of the erbium-doped fluoride fiber laser, comprising the steps of:
the pump laser generates pump light;
and after being combined by the beam combiner, the pump light is coupled into an inner cladding and a fiber core of the double-cladding erbium-doped fluoride optical fiber, is oscillated in the first optical resonant cavity and the second optical resonant cavity to form laser, and is converted into laser by the AlF3And (4) outputting by an end cap.
The invention has the beneficial effects that the invention provides the erbium-doped fluoride fiber laser and the laser generation method, the first fiber Bragg grating and the third fiber Bragg grating which are highly reflective to 1.6 mu m laser are adopted to bind the 1.6 mu m laser generated by the particle transition of the traditional 2.8 mu m erbium-doped fluoride fiber laser in the second resonant cavity and repeatedly oscillate, and finally the laser is excited by the excited state energy level of erbium ions4I13/2Absorption pumping to energy level4I9/2And then relax back to the energy level by multiphoton relaxation4I11/2Not only the 1.6 μm laser is recycled, but also the energy level is enabled4I13/2The particles are recycled, so that the energy utilization rate of the laser is greatly improved, and the slope efficiency and the output power of the laser radiation of the 2.8-micron optical fiber laser are obviously increased; and the laser has compact integral structure, stable work and high efficiency, is suitable for obtaining high-power 2.8 mu m laser output, and is easy to realize commercialization.
Drawings
Fig. 1 is a schematic structural diagram of an erbium-doped fluoride fiber laser provided by the present invention;
FIG. 2 is a flow chart of an embodiment of a laser generation method provided by the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As the laser with the wave band of 2.8 mu m in the prior art adopts 976nm laser pumping erbium-doped ion fluoride optical fiber, the energy level is high4I11/2Sum energy level4I13/2While laser radiation of 2.8 μm is formed, because erbium ions are at the excitation level4I13/2Upper ion retention time much greater than at higher energy levels4I11/2Resulting in self-termination of the laser energy level transition and at the energy level4I13/2And energy level4I15/2The 1.6 μm laser is generated between the two lasers, so that the efficiency of the fiber laser is reduced, the energy is not utilized, a large amount of heat is generated, and the further improvement of the output power of the laser is limited. In order to solve the above problems, the present invention provides an erbium fluoride-doped fiber laser, as shown in fig. 1. The optical fiber laser of the present invention includes: at least one pump laser 1, a beam combiner 2, a first fiber Bragg grating 3, a second fiber Bragg grating 4, a double-clad erbium-doped fluoride fiber 5, a third fiber Bragg grating 6 and AlF3And an end cap 8. The number of the pump lasers 1 used for generating pump light may be one or multiple, and as shown in fig. 1, two pump lasers 1 are provided; the pump laser 1 is connected with the beam combiner 2 and is used for combining the pump light generated by the pump laser 1 into one beam; the second fiber Bragg grating 4 and the AlF3The end cap 8 forms a first optical resonant cavity in which the double-clad erbium-doped fluoride fibre 5 is located; the first fiber bragg grating 3 and the third fiber bragg grating 6 form a second optical resonant cavity, and the double-clad erbium-doped fluoride fiber 5 is also positioned in the second optical resonant cavity.In a specific application process, after being combined by the beam combiner 2, the pumping light is coupled into an inner cladding and a fiber core of the double-cladding erbium-doped fluoride optical fiber 5, and oscillates in the first optical resonant cavity to generate 2.8 μm laser, and the 1.6 μm laser generated by particle transition is bound in the second optical resonant cavity to be subjected to energy level4I13/2The erbium ions absorb and reuse to generate 2.8 mu m laser, and the low quantum efficiency and stability of the optical fiber laser are improved. The optical fiber laser in the embodiment can obtain high-efficiency 2.8 mu m laser by the double-cladding erbium-doped fluoride optical fiber and the optical fiber Bragg grating, has compact integral structure and high working stability and efficiency, and is easy to realize commercialization.
In specific implementation, in this embodiment, the wavelength of the pump light generated by the pump laser 1 is 976nm, the working wavelength of the beam combiner 2 is also 976nm, and the pump light of 976nm generated by the pump laser 1 passes through the beam combiner 2 and is combined into one beam. The double-clad erbium-doped fluoride optical fiber 5 comprises an inner cladding and a fiber core, wherein the inner cladding has large numerical aperture and cladding diameter and plays a role in multimode laser transmission, the fiber core is doped with rare earth metal elements, namely erbium ions in the embodiment, and the refractive index of the fiber core is larger than that of the inner cladding. The tail fiber of the combiner 2 and the end face of the double-clad erbium-doped fluoride optical fiber 5 are welded and bonded together by a special method to form a passage. The combined pump light enters the inner cladding of the double-cladding erbium-doped fluoride optical fiber 5 and is reflected by the inner cladding, and the pump light excites the energy level in the fiber core by passing through the fiber core for multiple times4I15/2Upper ground state erbium ions pumped to the energy level4I11/2Thereby forming population inversion so as to be at an energy level4I11/2Sum energy level4I13/2Forming 2.8 μm laser radiation. Compared with the common optical fiber, the double-clad erbium-doped fluoride optical fiber 5 has the advantages that the pumping light efficiency is improved by the inner cladding with larger diameter, and the light source quality is ensured by the fiber core with smaller diameter.
In specific implementation, in this embodiment, a second fiber bragg grating 4 is inscribed on the double-clad erbium-doped fluoride optical fiber 5 near the pump light injection side, and the second fiber bragg gratingThe reflectivity of the grating 4 to 2.8 mu m laser is more than 99%, and the working bandwidth is less than 0.9nm, so that the second fiber Bragg grating 4 and the AlF3The end cap 8 forms a first optical resonant cavity that is highly reflective of the 2.8 μm laser light generated within the cavity and highly transmissive of the pump light. The pumping light is coupled into an inner cladding of a double-cladding erbium-doped fluoride optical fiber 5 through a beam combiner 2, erbium ions doped in the fiber core are excited to absorb by passing through the fiber core for multiple times, so that lower-level erbium ions transit to a high-energy level, once upper-level erbium ions are excited to radiate, light waves are formed and then transmitted back and forth between first optical resonant cavities, and when the gain of the light beams is larger than the loss, 2.8 mu m laser is obtained, and the AlF laser can pass through the AlF laser3End cap 8 outputs.
In specific implementation, the pump light excites erbium ions to change energy level4I11/2Transition to energy level4I13/2When 2.8 μm laser light is generated, on one hand, erbium ions are at the excitation level4I13/2Upper ion retention time (9.0ms) much greater than at higher energy levels4I11/2The residence time (6.9ms) and the erbium ions will come from a high level4I11/2Pumped to a higher energy level4F7/2Up thereby resulting in an energy level4I11/2The number of erbium ions decreases, and the number of particle inversions becomes insufficient, and the laser level transition self-terminates. On the other hand due to energy level4I13/2Is unstable, it will further transition to an energy level4I15/2The generation of 1.6 μm laser reduces the efficiency of the fiber laser and this part of the energy is not utilized, generating a lot of heat, limiting the further increase of the laser output power. In this embodiment, a first fiber bragg grating 3 is further inscribed on the side of the double-clad erbium-doped fluoride fiber 5 close to the pump light injection side, and a third fiber bragg grating 6 is inscribed on the side of the double-clad erbium-doped fluoride fiber 5 far from the pump light injection side. The reflectivity of the first fiber bragg grating 3 and the third fiber bragg grating 6 to the 1.6 μm laser is greater than 99%, the working bandwidth is less than 0.9nm, and the first fiber bragg grating 3 and the third fiber bragg grating 6 form a 1.6 μm laser resonant cavity, namely a second optical resonant cavity. Erbium ionFrom energy level4I13/2Transition to energy level4I15/2Generating 1.6 μm laser, binding in the second optical resonant cavity, oscillating repeatedly, and finally obtaining excited state energy level of erbium ion4I13/2Absorption pumping to energy level4I9/2And then relax back to the energy level by multiphoton relaxation4I11/2Energy level of4I11/2Can be transited to energy level by pump light4I13/22.8 μm laser is generated, so that not only the 1.6 μm laser is recycled, but also the energy level is enabled4I13/2The particles are recycled, the self-termination effect of the 2.8-micron laser oscillation is reduced, and the energy utilization rate of the laser is greatly improved.
In specific implementation, the inner cladding layer in the double-clad erbium-doped fluoride fiber 5 exists as a channel of pump light, and needs to have a large numerical aperture and a diameter sufficiently larger than that of the fiber core so as to facilitate the coupling of pump light. The inner cladding adopts a refractive index lower than that of the fiber core, and the excited information laser propagation is limited in the fiber core by means of total reflection. Preferably, in the present embodiment, the diameter of the inner cladding of the double-clad erbium-doped fluoride fiber 5 is 100 to 300 μm, and the diameter of the core of the double-clad erbium-doped fluoride fiber 5 is 10 to 30 μm. The large mode field and large numerical aperture design is beneficial to coupling high-power pump light into the gain fiber, fully interacting with rare earth ions of the fiber core and implementing effective pumping, thereby obtaining high-power laser output.
In specific implementation, in the embodiment, the double-clad erbium-doped fluoride fiber 5 has a doping amount of erbium ions of l% to 3% in terms of mole percentage, and the length of the double-clad erbium-doped fluoride fiber 5 is 15 to 20 m. In the foregoing steps, it is mentioned that in the laser used for generating a 2.8 μm band in the prior art, due to insufficient population inversion, the transition of the laser energy level is easily self-terminated, and in order to solve this problem, the mole percentage (more than 7%) of erbium ions in the erbium-doped fluoride fiber is generally increased to increase the population inversion, but this method, while increasing the population inversion, causes the heat generation of the laser to be serious, and limits the further increase of the laser output power. In this embodiment, the stress is 1.6 μmThe light is constrained in the second optical resonant cavity to repeatedly oscillate and can be excited to have an excited energy level4I13/2Is absorption pumped to an energy level4I9/2And then relax back to the energy level by multiphoton relaxation4I11/2The method solves the problem of self-termination of laser energy level transition, so that the doping amount of erbium ions in the double-clad erbium-doped fluoride fiber 5 is l% -3% in mole percentage, the length of the double-clad erbium-doped fluoride fiber 5 is 15-20 m, the slope efficiency of laser radiation of the fiber laser with the diameter of 2.8 mu m can be larger than 50%, and the laser works stably and generates less heat.
In practical implementation, although most of the pump light can be coupled into the inner cladding of the double-clad erbium-doped fluoride fiber 5 through the beam combiner 2 in this embodiment, a small part of the residual pump light still exists from AlF3End cap 8 outputs directly, thereby affecting AlF3End cap 8 outputs 2.8 μm laser light. Therefore, in this embodiment, the third fiber Bragg grating 6 and the AlF are arranged3A cladding mode stripper 7 is also arranged between the end caps 8, the cladding mode stripper 7 being arranged to filter out residual pump light such that AlF3End cap 8 outputs 2.8 μm laser light.
Further, since the tip of the double-clad erbium-doped fluoride fiber 5 is exposed to air, water vapor reacts with the tip of the double-clad erbium-doped fluoride fiber 5, increasing the hydroxyl contaminants on the surface of the double-clad erbium-doped fluoride fiber 5. According to fick's law, these hydroxyl impurities diffuse within the double-clad erbium-doped fluoride fiber 5, and the 2.8 μm laser radiation is strongly absorbed by the hydroxyl contaminants, resulting in local heating of the fiber tip, an increase in the diffusion process, and ultimately destruction of the double-clad erbium-doped fluoride fiber 5 tip. In this example, AlF3The end cap 8 outputs laser light, reduces catastrophic optical damage associated with hydroxyl diffusion in the tip of the double-clad erbium-doped fluoride fiber 5, prevents fiber end breakage, and provides 4% fresnel reflection as feedback for 2.8 μm laser light.
In addition, the present invention also provides a laser generation method of the erbium fluoride-doped fiber laser, as shown in fig. 2, which includes the following steps:
s1, generating pump light by a pump laser;
s2, after being combined by the beam combiner, the pump light is coupled into the inner cladding and the fiber core of the double-cladding erbium-doped fluoride optical fiber, and is oscillated in the first optical resonant cavity and the second optical resonant cavity to form laser and the laser is formed by AlF3And (4) outputting by an end cap.
In specific implementation, at least one pump laser is provided in this embodiment to generate pump light, and the pump light is coupled into the double-clad erbium-doped fluoride fiber after being combined into one beam by the beam combiner. Preferably, the wavelength of the pump light is 976nm, and the pump light is coupled into the inner cladding of the double-clad erbium-doped fluoride optical fiber after being combined by the beam combiner, and passes through the fiber core for multiple times to excite the energy level in the fiber core4I15/2Upper ground state erbium ions pumped to the energy level4I11/2Thereby forming population inversion so as to be at an energy level4I11/2Sum energy level4I13/2Forming 2.8 μm laser radiation. Then the second fiber Bragg grating and the AlF are arranged3When the gain of the light beam is larger than the loss, 2.8 μm laser light is obtained and is transmitted back and forth between the first optical resonant cavities formed by the end caps3And (4) outputting by an end cap.
In specific implementation, the pump light excites erbium ions to change energy level4I11/2Transition to energy level4I13/2When 2.8 μm laser light is generated, on one hand, erbium ions are at the excitation level4I13/2Upper ion retention time (9.0ms) much greater than at higher energy levels4I11/2The residence time (6.9ms) and the erbium ions will come from a high level4I11/2Pumped to a higher energy level4F7/2Up thereby resulting in an energy level4I11/2The number of erbium ions decreases, and the number of particle inversions becomes insufficient, and the laser level transition self-terminates. On the other hand due to energy level4I13/2Is unstable, it will further transition to an energy level4I15/2The generation of 1.6 μm laser causes the efficiency of the fiber laser to be reduced and this part of the energy is not availableThe laser is utilized, a large amount of heat is generated, and further improvement of the output power of the laser is limited. In this embodiment, a first fiber bragg grating is further written on the side of the double-clad erbium-doped fluoride fiber close to the pump light injection side, and a third fiber bragg grating is written on the side of the double-clad erbium-doped fluoride fiber far from the pump light injection side. The reflectivity of the first fiber Bragg grating and the third fiber Bragg grating to 1.6 mu m laser is more than 99%, the working bandwidth is less than 0.9nm, and the first fiber Bragg grating and the third fiber Bragg grating form a 1.6 mu m laser resonant cavity, namely a second optical resonant cavity. Energy level of erbium ion4I13/2Transition to energy level4I15/2Generating 1.6 μm laser, binding in the second optical resonant cavity, oscillating repeatedly, and finally obtaining excited state energy level of erbium ion4I13/2Absorption pumping to energy level4I9/2And then relax back to the energy level by multiphoton relaxation4I11/2Energy level of4I11/2Can be transited to energy level by pump light4I13/22.8 μm laser is generated, so that not only the 1.6 μm laser is recycled, but also the energy level is enabled4I13/2The particles are recycled, the self-termination effect of the 2.8-micron laser oscillation is reduced, and the energy utilization rate of the laser is greatly improved.
The invention is further illustrated by the following specific examples.
Examples 1
An erbium fluoride doped fibre laser, the fibre laser comprising:
as shown in FIG. 1, a 976nm pump laser 1, a beam combiner 2, a first fiber Bragg grating 3, a second fiber Bragg grating 4, a double-clad erbium-doped fluoride fiber 5, a third fiber Bragg grating 6, a clad mode stripper 7, an AlF3And an end cap 8.
The reflectivity of the second fiber Bragg grating 4 to 2.8 mu m laser is more than 99%, and the working bandwidth is less than 0.9 nm; the second fiber Bragg grating 4 and the AlF3The end caps 8 together form a first optical resonant cavity of the 2.8 μm band fibre laser,laser light having a wavelength of 2.8 μm generated from AlF3End cap 8 outputs.
The pump laser 1 outputs pump light with the wavelength of 976nm, and the pump light is coupled into the double-clad erbium-doped fluoride optical fiber 5 after being combined by the beam combiner 2.
The reflectivity of the first fiber Bragg grating 3 and the third fiber Bragg grating 6 to 1.6 mu m laser is higher than 99%, and the working bandwidth is less than 0.9 nm; the first fiber Bragg grating 3 and the third fiber Bragg grating 6 form a second optical resonant cavity, 1.6 mu m laser is constrained in the second optical resonant cavity to repeatedly vibrate, and finally all the laser is absorbed by excited erbium ions.
The double-clad erbium-doped fluoride fiber 5 is characterized in that the doping amount of erbium ions is l% in mole percentage, and the length of the double-clad erbium-doped fluoride fiber is 15 m.
The diameter of the inner cladding of the double-clad erbium-doped fluoride optical fiber 5 is 150 microns, and the diameter of the fiber core of the double-clad erbium-doped fluoride optical fiber 5 is 20 microns.
The pump laser 1 outputs pump light with the wavelength of 976nm, the pump light is coupled into an inner cladding of the double-cladding erbium-doped fluoride optical fiber 5 and is reflected to a fiber core after being combined by the beam combiner 2, and the pump light excites the energy level in the fiber core4I15/2Upper ground state erbium ion transition to energy level4I11/2Thereby forming population inversion so as to be at an energy level4I11/2Sum energy level4I13/2Laser radiation of 2.8 μm is formed therebetween with energy level4I13/2The excited erbium ion will further transition to the energy level4I15/2Pump light with the wavelength of 1.6 mu m is generated, the 1.6 mu m laser is bound in the second optical resonant cavity to repeatedly oscillate, and finally the pump light is excited by the excited state energy level of erbium ions4I13/2Absorption pumping to energy level4I9/2And then relax back to the energy level by multiphoton relaxation4I11/2Energy level of4I11/2Can be transited to energy level by pump light4I13/22.8 μm laser is generated, so that 1.6 μm laser is recycledSo that the energy level4I13/2The particles are recycled, the 2.8-micron laser oscillation self-termination effect is reduced, the energy utilization rate of the laser is greatly improved, the slope efficiency of 2.8-micron laser radiation is obviously increased, the slope efficiency reaches 51%, and the output power reaches 31W.
EXAMPLES example 2
An erbium fluoride doped fibre laser, the fibre laser comprising:
as shown in FIG. 1, a 976nm pump laser 1, a beam combiner 2, a first fiber Bragg grating 3, a second fiber Bragg grating 4, a double-clad erbium-doped fluoride fiber 5, a third fiber Bragg grating 6, a clad mode stripper 7, an AlF3And an end cap 8.
The reflectivity of the second fiber Bragg grating 4 to 2.8 mu m laser is more than 99%, and the working bandwidth is less than 0.9 nm; the second fiber Bragg grating 4 and the AlF3The end caps 8 together form a first optical resonant cavity of the 2.8 μm band fiber laser, and the generated laser with the wavelength of 2.8 μm is composed of AlF3End cap 8 outputs.
The pump laser 1 outputs pump light with the wavelength of 976nm, and the pump light is coupled into the double-clad erbium-doped fluoride optical fiber 5 after being combined by the beam combiner 2.
The reflectivity of the first fiber Bragg grating 3 and the third fiber Bragg grating 6 to 1.6 mu m laser is higher than 99%, and the working bandwidth is less than 0.9 nm; the first fiber Bragg grating 3 and the third fiber Bragg grating 6 form a second optical resonant cavity, 1.6 mu m laser is constrained in the second optical resonant cavity to repeatedly vibrate, and finally all the laser is absorbed by excited erbium ions.
The double-clad erbium-doped fluoride fiber 5 is characterized in that the doping amount of erbium ions is 3% in mole percentage, and the length of the double-clad erbium-doped fluoride fiber is 18 m.
The diameter of the inner cladding of the double-cladding erbium-doped fluoride optical fiber 5 is 200 mu m, and the diameter of the fiber core of the double-cladding erbium-doped fluoride optical fiber 5 is 15 mu m.
The pump laser 1 outputs pump light with the wavelength of 976nm, and the pump light is coupled into the beam combiner 2 after being combined by the beam combinerInto the inner cladding of said double-clad erbium-doped fluoride fiber 5 and reflected onto the core, exciting the energy level within the core4I15/2Upper ground state erbium ion transition to energy level4I11/2Thereby forming population inversion so as to be at an energy level4I11/2Sum energy level4I13/2Laser radiation of 2.8 μm is formed therebetween with energy level4I13/2The excited erbium ion will further transition to the energy level4I15/2Pump light with the wavelength of 1.6 mu m is generated, the 1.6 mu m laser is confined in the second optical resonant cavity to repeatedly oscillate, and finally the pump light is excited by the excited state energy level of erbium ions4I13/2Absorption pumping to energy level4I9/2And then relax back to the energy level by multiphoton relaxation4I11/2Energy level of4I11/2Can be transited to energy level by pump light4I13/22.8 μm laser is generated, so that not only the 1.6 μm laser is recycled, but also the energy level is enabled4I13/2The particles are recycled, the 2.8-micron laser oscillation self-termination effect is reduced, the energy utilization rate of the laser is greatly improved, the slope efficiency of 2.8-micron laser radiation is obviously increased, the slope efficiency reaches 53%, and the output power reaches 35W.
EXAMPLE 3
An erbium fluoride doped fibre laser, the fibre laser comprising:
as shown in FIG. 1, a 976nm pump laser 1, a beam combiner 2, a first fiber Bragg grating 3, a second fiber Bragg grating 4, a double-clad erbium-doped fluoride fiber 5, a third fiber Bragg grating 6, a clad mode stripper 7, an AlF3And an end cap 8.
The reflectivity of the second fiber Bragg grating 4 to 2.8 mu m laser is more than 99%, and the working bandwidth is less than 0.9 nm; the second fiber Bragg grating 4 and the AlF3The end caps 8 together form a first optical resonant cavity of the 2.8 μm band fiber laser, and the generated laser with the wavelength of 2.8 μm is composed of AlF3End cap 8 outputs.
The pump laser 1 outputs pump light with the wavelength of 976nm, and the pump light is coupled into the double-clad erbium-doped fluoride optical fiber 5 after being combined by the beam combiner 2.
The reflectivity of the first fiber Bragg grating 3 and the third fiber Bragg grating 6 to 1.6 mu m laser is higher than 99%, and the working bandwidth is less than 0.9 nm; the first fiber Bragg grating 3 and the third fiber Bragg grating 6 form a second optical resonant cavity, 1.6 mu m laser is constrained in the second optical resonant cavity to repeatedly vibrate, and finally all the laser is absorbed by excited erbium ions.
The erbium ion doping amount of the double-clad erbium-doped fluoride optical fiber 5 is 2% in mole percentage, and the length of the double-clad erbium-doped fluoride optical fiber 5 is 20 m.
The diameter of the inner cladding of the double-clad erbium-doped fluoride optical fiber 5 is 250 micrometers, and the diameter of the fiber core of the double-clad erbium-doped fluoride optical fiber 5 is 15 micrometers.
The pump laser 1 outputs pump light with the wavelength of 976nm, the pump light is coupled into an inner cladding of the double-cladding erbium-doped fluoride optical fiber 5 and is reflected to a fiber core after being combined by the beam combiner 2, and the pump light excites the energy level in the fiber core4I15/2Upper ground state erbium ion transition to energy level4I11/2Thereby forming population inversion so as to be at an energy level4I11/2Sum energy level4I13/2Laser radiation of 2.8 μm is formed therebetween with energy level4I13/2The excited erbium ion will further transition to the energy level4I15/2Laser with the wavelength of 1.6 μm is generated, the laser with the wavelength of 1.6 μm is bound in the second optical resonant cavity to repeatedly oscillate, and finally excited state energy level of erbium ions4I13/2Absorption pumping to energy level4I9/2And then relax back to the energy level by multiphoton relaxation4I11/2Energy level of4I11/2Can be transited to energy level by pump light4I13/22.8 μm laser is generated, so that not only the 1.6 μm laser is recycled, but also the energy level is enabled4I13/2The particles are recycled, the self-termination effect of 2.8 mu m laser oscillation is reduced, the energy utilization rate of a laser is greatly improved, and 2.8 mu m laser radiationThe slope efficiency is obviously increased, the slope efficiency reaches 55%, and the output power reaches 37W.
In summary, the present invention provides an erbium-doped fluoride fiber laser and a laser generation method, where the fiber laser includes: at least one pump laser, a beam combiner, a first fiber Bragg grating, a second fiber Bragg grating, a double-clad erbium-doped fluoride fiber, a third fiber Bragg grating, and an AlF3An end cap. The pump light generated by the first pump laser is coupled into the inner cladding of the double-cladding erbium-doped fluoride optical fiber at the erbium ion energy level4I11/2Sum energy level4I13/2While forming 2.8 μm laser radiation, the 1.6 μm laser is confined in the second optical resonant cavity formed by the first fiber Bragg grating and the third fiber Bragg grating for repeated oscillation, and finally excited state energy level of erbium ions4I13/2Absorption pumping to energy level4I9/2And then relax back to the energy level by multiphoton relaxation4I11/2Energy level of4I11/2Can be transited to energy level by pump light4I13/22.8 μm laser is generated, so that not only the 1.6 μm laser is recycled, but also the energy level is enabled4I13/2The particles are recycled, so that the self-termination effect of 2.8 mu m laser oscillation is reduced, and the energy utilization rate of the laser is greatly improved; and the laser adopts all-fiber integration, has compact integral structure, stable work and high efficiency, is suitable for obtaining high-power 2.8 mu m laser output, and is easy to realize commercialization.
It is to be understood that the system of the present invention is not limited to the above examples, and that modifications and variations may be made by one of ordinary skill in the art in light of the above teachings, and all such modifications and variations are intended to fall within the scope of the appended claims.

Claims (7)

1. The erbium-doped fluoride fiber laser is characterized by comprising at least one pumping laser, a beam combiner, a first fiber Bragg grating, a second fiber Bragg grating, a double-cladding erbium-doped fluoride fiber and a third fiber Bragg grating、AlF3An end cap; wherein the content of the first and second substances,
the pump laser is used for generating pump light;
the second fiber Bragg grating and the AlF3An end cap forming a first optical resonant cavity, said double-clad erbium-doped fluoride fiber being located within said first optical resonant cavity;
the first fiber Bragg grating and the third fiber Bragg grating form a second optical resonant cavity, and the double-cladding erbium-doped fluoride fiber is positioned in the second optical resonant cavity;
and after being combined by the beam combiner, the pump light is coupled into the inner cladding and the fiber core of the double-cladding erbium-doped fluoride optical fiber, oscillates in the first optical resonant cavity and the second optical resonant cavity to form laser, and is converted into laser by the AlF3An end cap output;
the reflectivity of the first fiber Bragg grating to the 1.6 mu m laser is more than 99 percent, and the working bandwidth is less than 0.9 nm;
the reflectivity of the third fiber Bragg grating to the laser with the wavelength of 1.6 mu m is more than 99 percent, and the working bandwidth is less than 0.9 nm;
the first fiber Bragg grating and the second fiber Bragg grating are inscribed on the double-cladding erbium-doped fluoride optical fiber close to the pump light injection side; the third fiber Bragg grating is inscribed on the side, far away from the pump light injection side, of the double-cladding erbium-doped fluoride fiber;
the 1.6 μm laser generated by particle transition is constrained in the second optical resonant cavity to repeatedly oscillate, and excited state energy level of erbium ion4I13/2Absorption pumping to energy level4I9/2And then relax back to the energy level by multiphoton relaxation4I11/2Energy level of4I11/2The particles of (2) are transited to energy levels by pump light4I13/2Generating 2.8 μm laser;
the fiber laser further comprises a cladding mode stripper;
the cladding mode stripper is positioned between the third fiber Bragg grating and the AlF3And between the end caps, for filtering out residual pump light.
2. An erbium-doped fluoride fiber laser as claimed in claim 1, wherein the pump light has a wavelength of 976 nm.
3. An erbium-doped fluoride fiber laser as claimed in claim 1, wherein the second fiber bragg grating has a reflectivity of greater than 99% for 2.8 μm laser light and an operating bandwidth of less than 0.9 nm.
4. An erbium-doped fluoride fiber laser as claimed in claim 1, wherein the beam combiner operating wavelength is 976 nm.
5. An erbium-doped fluoride fiber laser according to claim 1, wherein the inner cladding diameter of the double-clad erbium-doped fluoride fiber is 100 to 300 μm, and the core diameter of the double-clad erbium-doped fluoride fiber is 10 to 30 μm.
6. An erbium-doped fluoride fiber laser according to any one of claims 1 to 5, wherein the double-clad erbium-doped fluoride fiber has a doping amount of erbium ions of l% to 3% in mole percent, and the length of the double-clad erbium-doped fluoride fiber is 15 to 20 m.
7. A method of lasing an erbium fluoride fiber laser as claimed in any of claims 1 to 6, comprising the steps of:
the pump laser generates pump light;
and after being combined by the beam combiner, the pump light is coupled into an inner cladding and a fiber core of the double-cladding erbium-doped fluoride optical fiber, is oscillated in the first optical resonant cavity and the second optical resonant cavity to form laser, and is converted into laser by the AlF3And (4) outputting by an end cap.
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