CN120473802B - Pulse laser with all-fiber structure based on superfine single-crystal fiber and preparation method thereof - Google Patents
Pulse laser with all-fiber structure based on superfine single-crystal fiber and preparation method thereofInfo
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Abstract
一种基于超细单晶光纤的全光纤结构脉冲激光器及其制备方法，包括增益单晶光纤、脉冲调制单晶光纤，增益单晶光纤、脉冲调制单晶光纤之间通过热压键合形成超细单晶光纤异质键合结构；增益单晶光纤作为激光增益介质，脉冲调制单晶光纤作为可饱和吸收体，增益单晶光纤上设有高反射光栅以及脉冲调制单晶光纤尾端设有的斜角低反端构成谐振腔，泵浦光输入增益单晶光纤经高反射光栅进入谐振腔，由斜角低反端输出脉冲激光。本发明通过超细单晶光纤键合技术将增益段与调制段融合为一体化结构，并利用飞秒激光直写技术刻写高反射光栅，在输出端进行低反射镜斜角处理，消除空间耦合损耗，实现全光纤单片集成。
An all-fiber pulsed laser based on ultrafine single-crystal fiber and its fabrication method include a gain single-crystal fiber and a pulse-modulated single-crystal fiber, which are thermally bonded to form an ultrafine single-crystal fiber heterojunction structure. The gain single-crystal fiber serves as the laser gain medium, the pulse-modulated single-crystal fiber serves as a saturable absorber, and a high-reflection grating is provided on the gain single-crystal fiber. An angled low-reflection end is provided at the end of the pulse-modulated single-crystal fiber to form a resonant cavity. Pump light is input into the gain single-crystal fiber through the high-reflection grating and enters the resonant cavity, where pulsed laser light is output from the angled low-reflection end. The invention integrates the gain and modulation sections into an integrated structure through ultrafine single-crystal fiber bonding technology, and utilizes femtosecond laser direct writing technology to inscribe the high-reflection grating. A low-reflection mirror is angled at the output end to eliminate spatial coupling loss, achieving all-fiber monolithic integration.
Description
Technical Field
The invention mainly relates to the technical field of fiber lasers, in particular to an all-fiber structure pulse laser based on superfine single crystal fiber and a preparation method thereof.
Background
Along with the wide application of the ultrafast pulse laser technology in the fields of precision machining, biomedicine, quantum communication and the like, higher requirements are put on miniaturization, integration and performance stability of the pulse laser. The traditional pulse laser mostly adopts a discrete structure, and the gain medium, the modulation device and the resonant cavity are coupled through a space optical element, so that the problems of huge volume, complex assembly, easy environmental interference and the like exist. In recent years, single crystal optical fibers have been increasingly used as an ideal carrier for high-power lasers due to their excellent optical waveguide properties, high thermal stability, and high damage threshold. Meanwhile, the maturation of the femtosecond laser micromachining technology provides a new approach for the micro-nano structure integration of the optical fiber device, for example, the micro-cavity, the grating and other structures can be directly etched in or on the surface of the optical fiber by the femtosecond laser direct writing technology, so that the high-precision integration of the functional device is realized.
The traditional scheme adopts a cascade of bulk gain crystals (such as Nd: YAG) and nonlinear crystals (such as KTP), and pulse output is realized through an external modulator and a resonant cavity combination. For example, a composite gain passively modulated microchip laser is proposed in the patent application publication CN104852263a, where the sub-pulses are suppressed by bonding different gain media through optical bonding. However, such designs rely on complex spatial optical alignment, resulting in large system volumes, high coupling losses (typically > 10%), and low bulk crystal utilization (effective mode field only 1% -5% of the material cross section). In addition, the nonlinear frequency conversion process is easily influenced by the space walk-off effect, and the energy conversion efficiency is limited.
In recent years, the integration of gain and nonlinear functions is realized by the single crystal optical fiber through a bonding technology, for example, the single crystal optical fiber integrating fundamental frequency gain and nonlinear frequency conversion adopts a bonding-before-drawing technology in the patent technology, so that the fundamental frequency gain optical fiber and the nonlinear optical fiber are fused into a coupling-free structure, and the walk-off effect is remarkably reduced. However, the resonant cavity is realized by coating films at two ends of the single crystal optical fiber, the coating process is complex, the commercialized development is inconvenient, and the damage threshold of the conventional medium film (such as HfO 2/SiO2) coated with is about 12.8J/cm < 2> -15.3J/cm < 2>, so that the method is difficult to be applied to extreme environments such as high temperature, high pressure and the like.
On the other hand, photonic Crystal Fibers (PCF) can realize dispersion regulation and nonlinear enhancement by designing microstructures (such as air hole arrays), but the preparation process is complex, and the doped region and the microcavity structure are difficult to precisely match, so that the Q value is low (generally <10≡4).
The femtosecond laser wet etching or two-photon polymerization technology can be used for preparing an optical fiber microcavity, such as etching a Fabry-Perot microcavity or a Mach-Zehnder interference structure on the end face of the optical fiber, and is applied to strain and refractive index sensing. However, such microcavities are often independent of the gain medium, requiring additional introduction of modulation elements (e.g., saturable absorbers), resulting in increased system complexity. In addition, the heterogeneous interface of the microcavity and the gain fiber is easy to introduce scattering loss, and the output power and the beam quality are limited.
Traditional solid-state laser schemes rely on spatial optics and are difficult to implement for all-fiber integration of gain, modulation and resonance functions, resulting in bulky volumes and poor stability. The low utilization rate of bulk crystal, heterogeneous interface loss and space walk-off effect significantly restrict energy conversion efficiency (usually < 30%), and have laser output efficiency and power bottlenecks. Conventional fiber lasers are limited by the low melting point, low thermal conductivity of the glass material itself and are difficult to apply in extreme environments. The single crystal optical fiber combines the excellent physical and chemical properties of the crystal material and the structural advantages of the large specific surface area of the glass optical fiber, is suitable for extreme environments such as high temperature, high pressure and the like, but is still similar to the application mode of bulk crystal as a laser gain medium at present, and is not beneficial to the miniaturized application of a laser. The existing single crystal optical fiber bonding technology is difficult to be compatible with a microcavity processing technology, and the complex microstructure of the photonic crystal optical fiber limits the flexibility of doping and function integration.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides an all-fiber structure pulse laser based on an ultrafine single crystal fiber and a preparation method thereof.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
The pulse laser with the all-fiber structure based on the ultra-fine single crystal fiber comprises a gain single crystal fiber and a pulse modulation single crystal fiber, wherein the gain single crystal fiber and the pulse modulation single crystal fiber form an ultra-fine single crystal fiber heterogeneous bonding structure through thermocompression bonding, the gain single crystal fiber is used as a laser gain medium, the pulse modulation single crystal fiber is used as a saturable absorber, a high reflection grating is arranged on the gain single crystal fiber, an oblique angle low-reflection end arranged at the tail end of the pulse modulation single crystal fiber forms a resonant cavity, the pumping light enters the resonant cavity through the high reflection grating, and pulse laser is output from the oblique angle low-reflection end.
Preferably, the gain single crystal fiber is an Nd 3+ doped single crystal fiber, the doping concentration of Nd 3+ ions is 0.8-at-1.2-at%, and Nd 3+ ions in the gain single crystal fiber can generate 1064-nm laser under pumping light with the wavelength of 808-nm.
Preferably, the gain single crystal fiber is a Yb 3+ doped single crystal fiber, the doping concentration of Yb 3+ ions is 0.8-at-1.2-at%, and Yb 3+ ions in the gain single crystal fiber can generate 1030 nm laser under the pumping of pumping light with the wavelength of 976-nm.
Preferably, the crystal matrix of the gain single crystal fiber is garnet-structured crystal or tetragonal crystal or sesquioxide crystal.
Preferably, the pulse modulation single crystal optical fiber is a Cr 4+ doped single crystal optical fiber, the doping concentration of Cr 4+ is 0.05at.% to 0.1at.%, the Cr 4+ doped single crystal optical fiber is used as a saturable absorber, the modulation bandwidth covers 1000nm to 1200nm, the requirement of modulating Nd 3 + doped single crystal optical fiber or Yb 3+ doped single crystal optical fiber laser is met, the modulation depth delta T=10%, and the saturation flux is 0.1J/cm < 2 >.
Preferably, the crystalline matrix of the pulse modulated single crystal fiber is a YAG crystal, YVO 4 crystal, znSe crystal, or ZnS crystal.
On the other hand, the preparation method of the pulse laser with the all-fiber structure based on the superfine single crystal fiber comprises the following steps:
(1) Preparing a gain single crystal optical fiber and a pulse modulation single crystal optical fiber, wherein the gain single crystal optical fiber is Nd 3+ doped single crystal optical fiber, the pulse modulation single crystal optical fiber is Cr 4+ doped single crystal optical fiber, and crystal matrixes of the gain single crystal optical fiber and the pulse modulation single crystal optical fiber are YAG crystals;
(2) Preparing an ultrafine single crystal optical fiber heterogeneous bonding structure;
(2.1) polishing the end surfaces of the gain single crystal optical fiber and the pulse modulation single crystal optical fiber, performing chemical cleaning, placing the two sections of optical fibers in hydrofluoric acid for ultrasonic cleaning, removing surface pollutants, flushing with deionized water and ultrapure water to remove residues, and finally placing in a vacuum drying oven to remove water residues;
Performing hot-press bonding in a vacuum cavity, wherein the pressure of the vacuum cavity is less than or equal to 10 -3 Pa, CO 2 laser with the power of 30W and the spot diameter of 100 mu m is adopted to perform hot-press bonding on the contact surface of the gain section single crystal optical fiber and the modulation section single crystal optical fiber, the bonding temperature is controlled to be 85 percent of the melting point of a crystal matrix, the pressurizing time is 10 seconds, the pressure is 20MPa, a diameter gradient region is formed at the bonding interface of the gain single crystal optical fiber and the modulation single crystal optical fiber through CO 2 laser heating and stretching, the adiabatic transition of the mode field diameter is realized, the temperature is reduced to 800 ℃ at the speed of 5 ℃ per min after the hot-press bonding is finished, and the annealing is performed for 2 hours at the temperature of 800 ℃ to eliminate the interface stress;
(3) Coating the whole optical fiber with ultraviolet curing glue, and coating an SiC heat sink layer on the outer layer to ensure the matching of thermal expansion coefficients;
(4) The method comprises the steps of writing a high-reflection grating on a gain single crystal optical fiber at a position close to a laser input end by using a femtosecond laser direct writing method, performing bevel cutting treatment on the tail end of the pulse modulation single crystal optical fiber to form an 8-degree bevel end face, coating an anti-reflection coating on the bevel end face to form a bevel low-reflection end, and using Fresnel reflection of the 8-degree bevel end face and an air interface and combining the anti-reflection coating to enable the reflectivity of the bevel low-reflection end to be less than 0.1%.
Compared with the prior art, the invention has the technical effects that:
The gain section and the modulation section are integrated into a whole structure through an ultra-fine single crystal optical fiber bonding technology, a high reflection grating is inscribed at the input end of the single crystal optical fiber by utilizing a femtosecond laser direct writing technology, low reflection mirror oblique angle treatment is carried out at the output end, the space coupling loss is eliminated, and the full optical fiber monolithic integration is realized. The submicron processing precision of the femtosecond laser is combined, the precise spatial matching of the gain medium, the modulation function and the resonance function is realized, and the method is suitable for the output requirement of the miniaturized high repetition frequency (MHz level) femtosecond laser in an extreme environment. The invention is suitable for extreme environments such as high temperature and high pressure which cannot be applied to the traditional glass optical fiber by virtue of the characteristics of high melting point and the like of the single crystal optical fiber, and simultaneously solves the problem that the existing single crystal optical fiber laser still needs space coupling and cannot be integrated.
Compared with the photonic crystal fiber, the single crystal fiber has no grain boundary and air hole, low intrinsic loss and small doping concentration gradient, and can ensure high overlapping of the gain region and the resonance mode field. The single crystal fiber femtosecond laser direct writing is used for replacing photonic crystal fiber air hole drawing, and the production yield and the process efficiency are obviously improved.
The invention constructs the resonant cavity on the gain modulation integrated single crystal optical fiber by inscribing the Bragg grating and the bevel angle, does not need to be externally added with the resonant cavity, is beneficial to miniaturization of devices, can exert the advantages of high melting point and high heat conductivity of the single crystal optical fiber, and is suitable for environments such as high temperature, high pressure and the like.
The pulse laser with the all-fiber structure based on the superfine single-crystal fiber has miniaturization, high stability and extreme environmental adaptability, fills the technical blank of the all-fiber pulse laser in a high-temperature high-pressure scene, and has great application value in the fields of energy exploration, aerospace and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an all-fiber structure pulse laser based on ultra-fine single crystal fiber in one embodiment.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, an all-fiber structure pulse laser based on ultra-fine single crystal fiber is provided, which comprises a gain single crystal fiber 3 and a pulse modulation single crystal fiber 5. The gain single crystal optical fiber 3 and the pulse modulation single crystal optical fiber 5 are bonded through hot pressing to form an ultra-fine single crystal optical fiber heterogeneous bonding structure 4, the gain single crystal optical fiber 3 is used as a laser gain medium, the pulse modulation single crystal optical fiber 5 is used as a saturable absorber, the gain single crystal optical fiber 3 is provided with a high reflection grating 2, an oblique angle low-reflection end 6 arranged at the tail end of the pulse modulation single crystal optical fiber 5 forms a resonant cavity, pump light 1 is input into the gain single crystal optical fiber 3 and enters the resonant cavity through the high reflection grating 2, and pulse laser 7 is output through the oblique angle low-reflection end 6. The gain single crystal optical fiber is Nd 3+ doped single crystal optical fiber or Yb 3+ doped single crystal optical fiber. The crystal matrix of the gain single crystal optical fiber comprises, but is not limited to, garnet structure crystals such as YAG and LuAG, tetragonal crystals such as CGA, and the like, the Lu 2O3 is a sesquioxide crystal with the diameter of 30-200 μm, the length of the gain single crystal optical fiber is set (1-100 cm) according to application requirements, and the end face is polished until the surface roughness Ra is less than 1nm. The pulse modulation single crystal optical fiber is a Cr 4+ doped single crystal optical fiber, the doping concentration of Cr 4+ is 0.05at.% to 0.1at.%, and the crystal matrix of the pulse modulation single crystal optical fiber comprises but is not limited to YAG crystals, YVO 4 crystals, znSe crystals or ZnS crystals, the diameter of the pulse modulation single crystal optical fiber is matched with the gain section, the length is 5-20 mm, and the output end face inclined angle is 8 degrees so as to inhibit echo reflection. The Cr 4+ doped single crystal optical fiber is used as a saturable absorber, the modulation bandwidth covers 1000nm-1200nm, the requirement of modulating Nd 3+ doped single crystal optical fiber or Yb 3+ doped single crystal optical fiber laser is met, the modulation depth delta T=10%, the saturation flux is 0.1J/cm < 2 >, and the saturation flux is matched with the relaxation time of a gain section (tau approximately 30 mu s).
The invention adopts the cooperative design of ultra-fine single crystal fiber bonding and femtosecond laser Bragg grating direct writing to construct an all-fiber pulse laser device based on gain-modulation-resonance function integration of ultra-fine single crystal fiber. The pump light 1 is incident to the input end face of the gain single crystal optical fiber 3, the gain single crystal optical fiber 3 is used as a laser gain medium, the pulse modulation single crystal optical fiber 5 is used as a saturable absorber, the resonant cavity is composed of a femtosecond direct-writing high-reflection grating 2 and an oblique angle low-reflection end 6, and finally pulse laser 7 is output.
In a preferred embodiment, based on the structure shown in fig. 1, an all-fiber pulse laser based on ultra-fine single crystal fiber is provided, which comprises a gain single crystal fiber 3, a pulse modulation single crystal fiber 5, a gain single crystal fiber 3 and a pulse modulation single crystal fiber 5, wherein the ultra-fine single crystal fiber heterojunction structure 4 is formed by thermocompression bonding, the gain single crystal fiber 3 is used as a laser gain medium, the pulse modulation single crystal fiber 5 is used as a saturable absorber, the gain single crystal fiber 3 is an Nd 3+ doped single crystal fiber, the doping concentration of Nd 3+ ions is 0.8 at% -1.2 at%, and Nd 3+ ions in the gain single crystal fiber 3 can generate 1064 nm laser under pumping light with the wavelength of 808 nm. Other arrangements of the present embodiment, including the crystal matrix of the gain single crystal optical fiber 3, the crystal matrix of the pulse modulation single crystal optical fiber 5, and the doping type can be the same as those of the foregoing embodiment, and will not be described herein.
In a preferred embodiment, based on the structure shown in fig. 1, an all-fiber pulse laser based on ultra-fine single crystal fiber is provided, which comprises a gain single crystal fiber 3, a pulse modulation single crystal fiber 5, a gain single crystal fiber 3 and a pulse modulation single crystal fiber 5, wherein the ultra-fine single crystal fiber heterojunction bonding structure 4 is formed by thermocompression bonding, the gain single crystal fiber 3 is used as a laser gain medium, the pulse modulation single crystal fiber 5 is used as a saturable absorber, the gain single crystal fiber 3 is a Yb 3+ doped single crystal fiber, the doping concentration of Yb 3+ ions is 0.8-at% -1.2 at%, and Yb 3+ ions in the gain single crystal fiber 3 can generate 1030 nm laser under pumping light with the wavelength of 976 nm. Other arrangements of the present embodiment, including the crystal matrix of the gain single crystal optical fiber 3, the crystal matrix of the pulse modulation single crystal optical fiber 5, and the doping type can be the same as those of the foregoing embodiment, and will not be described herein.
In one embodiment, a method for preparing an all-fiber structure pulse laser based on ultra-fine single crystal fiber is provided, comprising:
(1) Preparing a gain single crystal optical fiber 3 and a pulse modulation single crystal optical fiber 5, wherein the gain single crystal optical fiber 3 is Nd 3+ doped single crystal optical fiber, the pulse modulation single crystal optical fiber 4 is Cr 4+ doped single crystal optical fiber, and crystal matrixes of the gain single crystal optical fiber 3 and the pulse modulation single crystal optical fiber 5 are YAG crystals;
(2) Preparing an ultra-fine single crystal optical fiber heterogeneous bonding structure 4;
(2.1) polishing the end surfaces of the gain single crystal optical fiber 3 and the pulse modulation single crystal optical fiber 5, performing chemical cleaning, placing the two sections of optical fibers in hydrofluoric acid for ultrasonic cleaning to remove surface pollutants, washing with deionized water and ultrapure water to remove residues, and finally placing in a vacuum drying oven to remove water residues;
Performing hot-press bonding in a vacuum cavity, wherein the pressure of the vacuum cavity is less than or equal to 10 -3 Pa, CO 2 laser with the power of 30W and the spot diameter of 100 mu m is adopted to perform hot-press bonding on the contact surface of the gain section single crystal optical fiber and the modulation section single crystal optical fiber, the bonding temperature is controlled to be 85 percent of the melting point of a crystal matrix, the pressurizing time is 10 seconds, the pressure is 20MPa, a diameter gradient region is formed at the bonding interface of the gain single crystal optical fiber and the modulation single crystal optical fiber through CO 2 laser heating and stretching, the adiabatic transition of the mode field diameter is realized, the temperature is reduced to 800 ℃ at the speed of 5 ℃ per minute after the hot-press bonding is finished, and the interface stress is eliminated by annealing for 2 hours at 800 ℃ to obtain the superfine single crystal optical fiber heterogeneous bonding structure;
(3) Coating the whole optical fiber with ultraviolet curing glue, and coating an SiC heat sink layer on the outer layer to ensure the matching of thermal expansion coefficients;
(4) The method comprises the steps of writing a high-reflection grating on a gain single crystal optical fiber 3 near a laser input end by using a femtosecond laser direct writing method, performing chamfering treatment on the tail end of a pulse modulation single crystal optical fiber 5 to form an 8-DEG bevel end face, coating an anti-reflection coating on the bevel end face to form a bevel low-reflection end, and using Fresnel reflection of the 8-DEG bevel end face and an air interface and combining the anti-reflection coating to enable the reflectivity of the bevel low-reflection end to be less than 0.1%.
Thus, the preparation of the pulse laser with the all-fiber structure based on the superfine single crystal fiber is completed.
The melting points of single crystal fibers and glass fibers are different, and conventional fusion and bonding processes are not suitable. Before the gain single crystal optical fiber 3 and the pulse modulation single crystal optical fiber 5 are thermally bonded, the end faces of the gain single crystal optical fiber 3 and the pulse modulation single crystal optical fiber 5 are polished, chemical cleaning is carried out, two sections of optical fibers are placed in hydrofluoric acid (concentration of 5%) for ultrasonic cleaning for 5 minutes, surface pollutants are removed, deionized water and ultrapure water are used for flushing to remove residues, and finally the optical fibers are placed in a vacuum drying oven to remove water residues. And then the gain single crystal optical fiber 3 and the pulse modulation single crystal optical fiber 5 are thermally pressed and bonded in a vacuum cavity (the pressure is less than or equal to 10 -3 Pa), laser (CO 2 laser, the power is 30W, the spot diameter is 100 μm) is adopted for local heating to thermally press and bond the contact surface of the gain section single crystal optical fiber and the modulation section single crystal optical fiber, the bonding temperature is controlled at 85 percent (YAG about 1600 ℃) of the melting point of a crystal matrix, the pressing time is 10 seconds, and the pressure is 20MPa. A diameter gradient region (the diameter distribution form of the diameter gradient region is that the diameter is changed from large to small and then is changed to large, for example, the diameter is changed from 50 μm to 30 μm and then is changed from 30 μm to 50 μm) is formed at the bonding interface of the gain single crystal optical fiber and the modulation single crystal optical fiber by CO 2 laser heating and stretching, and adiabatic transition of the mode field diameter (for example, from 5.6 μm (Nd: YAG) to 4.2 μm (Cr: YAG)) is realized. After bonding, the temperature was reduced to 800 ℃ at a rate of 5 ℃ per minute and annealed at that temperature for 2 hours to relieve interfacial stress. Finally, ultraviolet curing glue (refractive index 1.45) is adopted to wrap the optical fiber, and an SiC heat sink layer (thickness 100 mu m) is coated on the outer layer to ensure the matching of the thermal expansion coefficients.
When a high-reflection grating is inscribed on a gain single crystal optical fiber 3 at a position close to a laser input end by using a femtosecond laser direct writing method, a femtosecond laser with 1030nm wavelength, 290fs pulse width, 100kHz repetition frequency and 1.5 mu J single pulse energy is adopted to etch a Bragg grating with a period of lambda=1.5 mu m in a spiral scanning mode along the axial direction of the optical fiber, the grating length is 2mm, the duty ratio is 50%, the local amorphization of an optical fiber material is induced by controlling the energy density of the femtosecond laser within the range of 3J/cm2-5J/cm2, a periodic structure with a refractive index difference delta n=0.005 is formed, the reflectivity of the inscribed high-reflection grating is >99.5% (@ 1064 nm), the bandwidth is 10nm, and the temperature drift coefficient is <0.01nm/°c.
When the high-reflection grating is written on the gain single crystal optical fiber by using the femtosecond laser direct writing method, the adopted femtosecond laser has the wavelength of 1030 nm, the pulse width of 290 fs, the repetition frequency of 100 kHz and the single pulse energy of 1.5 mu J. The traditional femtosecond laser direct writing grating technology is mainly aimed at glass optical fibers (such as quartz) or polycrystalline materials, and is not applicable to single crystal optical fiber materials. The invention comprehensively considers the nonlinear absorption mechanism, the thermal diffusion effect and the lattice order limitation of the single crystal when performing femtosecond laser direct writing on the single crystal optical fiber, realizes precise thermal control and stabilizes the formation of amorphous phase. The femtosecond laser induces the local amorphization of the single crystal optical fiber material, the refractive index modulation depth is about-0.005, and the grating structure with a proper period is inscribed along the axial direction of the optical fiber by a femtosecond laser surface-by-surface inscribing method, so that the preparation of the high-reflection grating with specific wavelength can be realized.
When the tail end of the pulse modulated single crystal optical fiber 5 is subjected to the beveling treatment, the Fresnel reflection (R is about 0.4%) of an 8 DEG bevel end face and an air interface is utilized, and the anti-reflection coating (MgF 2, the thickness lambda/4=266 nm) is combined, so that the reflectivity of the bevel low opposite end is reduced to be less than 0.1%.
Finally, the prepared pulse laser with the all-fiber structure based on the superfine single crystal fiber can be fixed in a V-shaped quartz groove, flexible silica gel (the heat conductivity coefficient is 1.5W/m.K) is filled in the groove, and the external packaging size is less than or equal to phi 3 multiplied by 50mm. And integrating micro-channels (with the width of 200 mu m) on the bonding surface of the gain section, and introducing deionized water to actively cool, wherein the thermal resistance is less than or equal to 0.5K/W.
The technical effect verification parameters are that the pulse width is less than 500fs, the repetition frequency is adjustable from 1MHz to 10MHz, the average power is more than 5W, and the beam quality M2 is less than 1.1 pulse laser output. The continuous operation of the device is ensured to have power fluctuation of +/-1% for 100 hours, and the temperature is in a working range of-20 ℃ to 60 ℃.
The invention systematically solves the problems of discrete structure, limited efficiency, insufficient process compatibility and the like in the prior laser technology under the application scene of high temperature and high pressure by adopting the integrated design of the ultra-fine gain single crystal optical fiber and the pulse modulation single crystal optical fiber bonding, the femtosecond laser direct writing Bragg grating and the function, and has the specific technical effects that the ultra-fine single crystal optical fiber heterojunction bonding and the femtosecond laser direct writing Bragg grating realize the all-fiber integration, the volume of a laser is reduced, the sensitivity of a space optical path to vibration and temperature drift is eliminated, and the compactness and the stability of the structure are obviously improved. By inhibiting the space walk-off effect and the heterogeneous interface loss, the conversion efficiency of the pump light and the signal light is greatly improved. The invention supports bonding of various single crystal optical fibers such as Nd, cr, YAG, yb, YAG and the like, can adapt to different wavelength requirements (1030 nm, 1064nm and the like), has crystal material compatibility, and allows integration of a plurality of functional units (such as DBR+microcavity+grating) in the same optical fiber by a femtosecond laser direct writing technology, thereby being applicable to development of sensing-laser integrated devices and being beneficial to high-precision functional integration. Through the collaborative innovation of material, process and structural design, the single-chip integration of the single-crystal fiber gain-modulation-resonance function is realized, the high-performance ultra-fast laser is output, the miniaturization, high stability and extreme environmental adaptability are achieved, the technical blank of the all-fiber ultra-fast laser in a high-temperature high-pressure scene is filled, and the method has great application value in the fields of energy exploration, aerospace and the like.
The invention is not a matter of the known technology.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples merely represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
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| CN113889831A (en) * | 2021-05-28 | 2022-01-04 | 中国科学院理化技术研究所 | Compact type strip pulse laser |
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| DE602004023531D1 (en) * | 2003-10-24 | 2009-11-19 | Koheras As | OPTICAL SYSTEM FOR PROVIDING SHORT LASER PULSE |
| CN102545027B (en) * | 2012-02-10 | 2013-08-21 | 厦门大学 | Yb: YAG (yttrium aluminum garnet) and Cr, Yb: YAG self-Q-switching laser |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104466633A (en) * | 2014-11-20 | 2015-03-25 | 天津大学 | High-power optical fiber laser device based on single crystal optical fiber |
| CN113889831A (en) * | 2021-05-28 | 2022-01-04 | 中国科学院理化技术研究所 | Compact type strip pulse laser |
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