Compact all-solid-state intracavity triple frequency deep ultraviolet laser

Abstract

The utility model relates to a compact all-solid-state intracavity triple frequency deep ultraviolet laser, and belongs to the technical field of lasers. The laser comprises a pumping source, a pumping coupler, a pumping end mirror, a laser crystal, a frequency doubling crystal, a frequency tripling crystal and an output mirror which are sequentially and linearly arranged along a light path, the laser crystal is a YLF crystal growing along a c axis by adopting a pulling method, and two linearly polarized lights with mutually vertical polarization directions are generated under a longitudinal pumping condition; the laser crystal, the frequency doubling crystal and the frequency tripling crystal are all cuboids, the pumping end mirror is a concave mirror, the output mirror is a plane mirror, and the pumping end mirror, the laser crystal, the frequency doubling crystal, the frequency tripling crystal and the output mirror form a linear resonant cavity. According to the utility model, the independently designed laser crystal and resonant cavity device are utilized to meet the polarization matching condition of I-type frequency doubling and I-type frequency tripling, so that the output wavelength of frequency tripling is greatly expanded to a deep ultraviolet band.

Description

TECHNICAL FIELD

[0001] The utility model relates to a compact full solid-state intracavity third harmonic generation deep ultraviolet laser belongs to laser technical field. BACKGROUND

[0002] At present, intracavity third harmonic generation solid-state laser generally adopts the mode of I class frequency multiplication + II class third harmonic generation, and the 355nm ultraviolet laser commonly seen in the market is due to the narrow phase matching range of II class third harmonic generation, so the technology of I class frequency multiplication + II class third harmonic generation cannot be applied to the generation of deep ultraviolet waveband solid-state laser below 300nm. In order to solve this problem, the utility model develops a compact full solid-state intracavity third harmonic generation laser, and the laser crystal can provide two mutually perpendicular sigma linearly polarized base frequency visible lasers, meets the polarization matching condition of I class frequency multiplication + I class third harmonic generation, so that the third harmonic output wavelength is greatly expanded to the deep ultraviolet waveband, and even reaches the vacuum ultraviolet waveband of 200nm.

[0003] The YLF crystal used in the existing laser is grown along the a axis or b axis, the YLF crystal belongs to the tetragonal system, is uniaxial in optics, and the a and b axes have similar physical properties, and are significantly different from the c axis. Since the pi polarized absorption coefficient of the YLF crystal doped with rare earth ions is large (E / / c), in order to improve the pump light absorption efficiency of the crystal and the overall efficiency of the laser, the existing YLF crystal is generally grown along the a axis or b axis to realize pi polarized absorption, which also brings three significant shortcomings: (1) only pi polarized (E / / c) or sigma polarized (E / / a or E / / b) laser can be generated, and such single-direction linearly polarized laser cannot meet the needs of two-direction linearly polarized laser for the intracavity I class frequency multiplication + I class third harmonic generation process; (2) growth stripes are easy to occur during the growth along the a axis or b axis, resulting in poor optical uniformity in the cross section, which is not conducive to commercial application; (3) thermal cracking is easy to occur during the growth along the a axis or b axis, especially under the condition of large pi polarized absorption coefficient. SUMMARY

[0004] In view of the deficiencies of the prior art, the utility model provides a compact full solid-state intracavity third harmonic generation deep ultraviolet laser.

[0005] The technical scheme of the utility model is as follows:

[0006] The utility model provides a compact all-solid-state intracavity tripling deep ultraviolet laser, including the linear arrangement of pump source, pump coupler, pump end mirror, laser crystal, frequency doubling crystal, tripling crystal and output mirror in turn along the light path, and the laser crystal is YLF crystal which is grown along the c axis by the pulling method, generates two linearly polarized lights which are perpendicular to each other in the polarization direction under the longitudinal pumping condition, and the laser crystal, the frequency doubling crystal and the tripling crystal are all cuboids, the pump end mirror is a concave mirror, and the output mirror is a plane mirror, and the pump end mirror, the laser crystal, the frequency doubling crystal, the tripling crystal and the output mirror form a linear resonant cavity.

[0007] According to the utility model, preferably, the pump source is a laser diode with spatial output or fiber coupling output, and the central wavelength is aligned with the polarization absorption peak of the laser crystal.

[0008] According to the utility model, preferably, the laser crystal is Pr:YLF, Dy:YLF or Tb:YLF, that is, the laser crystal is a YLF matrix crystal doped with praseodymium (Pr), dysprosium (Dy) or terbium (Tb) rare earth ions, and the doping concentration of the rare earth ions is 0.2-1 at.%, when the laser crystal is Pr:YLF, the central wavelength of the pump source is 442 nm, corresponding to the P1 energy level transition absorption peak of the Pr:YLF crystal 3 H4→ 3 P2 energy level transition absorption peak, when the laser crystal is Dy:YLF, the central wavelength of the pump source is 479 nm, corresponding to the P1 energy level transition absorption peak of the Dy:YLF crystal 6 H 15 / 2 → 4 F 9 / 2 energy level transition absorption peak, when the laser crystal is Tb:YLF, the central wavelength of the pump source is 488 nm, corresponding to the P1 energy level transition absorption peak of the Tb:YLF crystal 7 F6→ 5 D4 energy level transition absorption peak.

[0009] According to the utility model, preferably, the laser crystal, the frequency doubling crystal and the tripling crystal are all cuboids, the pump end mirror is a concave mirror, and the output mirror is a plane mirror, and the pump end mirror, the laser crystal, the frequency doubling crystal, the tripling crystal and the output mirror form a linear resonant cavity.

[0010] According to the utility model, preferably, the frequency doubling crystal material is BBO, LBO or BIBO, the frequency doubling crystal light transmission direction is a type frequency doubling phase matching (PM) direction of the fundamental frequency laser, and the two adjacent side surfaces are along the o-axis and e-axis directions of the frequency doubling crystal.

[0011] According to the utility model, preferably, the tripling crystal material is BBO or KBBF, the tripling crystal light transmission direction is a type sum frequency phase matching direction of the fundamental frequency laser and the frequency doubling laser, and the two adjacent side surfaces are along the o-axis and e-axis directions of the crystal.

[0012] According to the utility model, preferably, the pump end mirror concave curvature radius is 50 mm.

[0013] The utility model discloses the beneficial effect lies in:

[0014] 1, the utility model discloses utilize the laser crystal and the resonant cavity device of separate design satisfy the polarization matching condition of I type frequency multiplication + I type triple frequency, to make triple frequency output wavelength to deep ultraviolet waveband greatly expand. Such as for

[0015] 2, the utility model discloses adopt compact linear straight cavity, can maximum degree reduce the volume of laser, assemble convenient, reliable performance, facilitate large -scale, quick production, in the cavity triple frequency solid laser, common resonant cavity is V type cavity and Z type cavity etc. folding resonant cavity, adopt folding cavity can form multiple beam waist in the cavity, place the frequency doubling, triple frequency crystal to smaller beam waist place can improve the frequency doubling efficiency, but folding cavity element is many, and the loss is big, and there is astigmatism in the cavity, influence the quality of light spot, adopt the advantage of linear straight cavity is less element, compact structure, light path is easy to adjust, and the production cost is low, and the allowable range of pump power is bigger. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is the structural schematic diagram of the utility model;

[0017] Figure 2 It is the polarization matching principle schematic diagram of the utility model;

[0018] Among them: 1, pump source;2, pump coupler;3, pump end mirror;4, laser crystal;5, frequency doubling crystal;6, triple frequency crystal;7, output mirror. DETAILED DESCRIPTION

[0019] The utility model is further described below by embodiment and in conjunction with the drawings, but is not limited to this.

[0020] Example 1:

[0021] As Figure 1 Shown, the utility model provides a compact full solid cavity triple frequency deep ultraviolet laser, including the pump source 1 of linear arrangement in sequence along the light path, pump coupler 2, pump end mirror 3, laser crystal 4, frequency doubling crystal 5, triple frequency crystal 6 and output mirror 7, and the laser crystal 4 is YLF crystal using the pulling method along c axis growth, generates 2 polarized light of mutually perpendicular polarization direction under the condition of longitudinal pumping, along the a axis and b axis of laser crystal respectively, and the laser crystal 4, frequency doubling crystal 5 and triple frequency crystal 6 are all cuboids, and the pump end mirror 3 is a concave mirror, and the pump end mirror concave curvature radius is 50 mm, and the output mirror 7 is a plane mirror, and the pump end mirror 3, laser crystal 4, frequency doubling crystal 5, triple frequency crystal 6 and output mirror 7 form linear resonant cavity.

[0022] The resonant cavity has a cavity length of 57 mm, and the laser crystal has a size of 2*2*10 mm 3 The frequency-doubling crystal has a size of 3*3*10 mm 3 The tripling crystal has a size of 3*3*10 mm 3 .

[0023] The pump source 1 is a fiber-coupled laser diode, and the center wavelength is aligned with the polarization absorption peak of the laser crystal. The pump source fiber has a diameter of 200 μm, and the pump light is converged to the laser crystal through the pump end mirror, and the waist diameter is 224 μm.

[0024] The laser crystal 4 is Pr:YLF, and the center wavelength of the pump source is 442 nm, which corresponds to the Pr:YLF crystal 3 H4→ 3 P2 energy level transition absorption peak, linearly polarized fundamental laser wavelength is 607 nm, which corresponds to 3 P0→ 3 H6 radiation transition, the output light is 202.3 nm deep ultraviolet laser, and the two light transmission end faces of the laser crystal 4 are respectively coated with 442 nm and 607 nm antireflection dielectric films.

[0025] The frequency-doubling crystal 5 is BBO, LBO or BIBO, the light transmission direction of the frequency-doubling crystal is the I-type frequency-doubling phase matching (PM) direction of the fundamental laser, the two adjacent side faces are respectively along the o-axis and e-axis directions of the crystal, and the two light transmission end faces are respectively coated with 607 nm and 303.5 nm antireflection films.

[0026] The tripling crystal 6 is BBO or KBBF, the light transmission direction of the tripling crystal is the I-type sum frequency phase matching direction of the fundamental laser and the frequency-doubled laser, the two adjacent side faces are respectively along the o-axis and e-axis directions of the crystal, and the two light transmission end faces are respectively coated with 607 nm, 303.5 nm and 202.3 nm antireflection films.

[0027] The pump end mirror 3 is coated with a 442 nm high-transmission dielectric film on the light transmission surface facing away from the resonant cavity, and is coated with a 442 nm high-transmission, 607 nm and 303.5 nm high-reflection dielectric film on the light transmission surface facing the resonant cavity; the output mirror 7 is coated with a 202 nm high-transmission, 607 nm and 303.5 nm high-reflection dielectric film on the light transmission surface facing the resonant cavity, and is coated with a 202 nm high-transmission dielectric film on the light transmission surface facing away from the resonant cavity.

[0028] Each antireflection film and dielectric film is designed according to the corresponding light beam propagation position, which is a common design.

[0029] When working, as Figure 2As shown, (1) the laser emitted by the pump source passes through the pump coupler and the pump end mirror to inject the laser crystal, thereby generating 607nm linearly polarized fundamental laser with a-axis and b-axis two polarization directions perpendicular to each other; (2) after the fundamental laser enters the frequency doubling crystal, the linearly polarized fundamental light along the o-axis direction of the frequency doubling crystal occurs type I frequency doubling phase matching in the process of passing through the frequency doubling crystal, thereby generating 303.5nm linearly polarized frequency-doubled laser along the e-axis direction of the frequency doubling crystal, which together with the 607nm linearly polarized fundamental laser along the e-axis direction of the frequency doubling crystal enters the tripling frequency crystal; (3) the e-axis polarized 303.5nm frequency-doubled laser and the 607nm fundamental laser emitted by the frequency doubling crystal are both o-axis light relative to the tripling frequency crystal, which occurs type I sum frequency phase matching in the tripling frequency crystal, thereby generating 202.3nm linearly polarized sum frequency ultraviolet laser along the e-axis direction of the tripling frequency crystal, which is output by the output mirror.

[0030] Although the embodiments of the utility model have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the utility model, the scope of the utility model is defined by the appended claims and their equivalents.

Claims

1. A compact all-solid-state intracavity tripling deep-ultraviolet laser, characterized by, The pump source, the pump coupler, the pump end mirror, the laser crystal, the frequency doubling crystal, the third harmonic generation crystal and the output mirror are arranged in sequence along the light path.

2. The compact all-solid-state intracavity tripled deep UV laser as claimed in claim 1, wherein, The pump source is a laser diode with spatial output or fiber coupling output, and the central wavelength is aligned with the polarization absorption peak of the laser crystal.

3. The compact all-solid-state intracavity tripled deep UV laser as claimed in claim 2, wherein, The laser crystal is Pr:YLF, Dy:YLF or Tb:YLF, and the doping concentration of rare earth ions is 0.2-1 at.%.

4. The compact all-solid-state intracavity tripled deep UV laser as claimed in claim 3, wherein The laser crystal, the frequency doubling crystal and the third harmonic generation crystal are all cuboids, the pump end mirror is a concave mirror, and the output mirror is a plane mirror.

5. The compact all-solid-state intracavity tripled deep UV laser as claimed in claim 4, wherein The laser crystal is Pr:YLF, Dy:YLF or Tb:YLF, and the doping concentration of rare earth ions is 0.2-1 at.%.

6. The compact all-solid-state intracavity tripled deep UV laser as claimed in claim 5, wherein The laser crystal, the frequency doubling crystal and the third harmonic generation crystal are all cuboids, the pump end mirror is a concave mirror, and the output mirror is a plane mirror.

7. The compact all-solid-state intracavity tripled deep UV laser as claimed in claim 1, wherein The pump source is a laser diode with spatial output or fiber coupling output, and the central wavelength is aligned with the polarization absorption peak of the laser crystal. The laser crystal is Pr:YLF, Dy:YLF or Tb:YLF, and the doping concentration of rare earth ions is 0.2-1 at.%. The laser crystal, the frequency doubling crystal and the third harmonic generation crystal are all cuboids, the pump end mirror is a concave mirror, and the output mirror is a plane mirror. The pump end mirror has a concave curvature radius of 50 mm.

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