CN116706660A - Dual-material laser frequency doubling crystal and preparation method and application thereof - Google Patents
Dual-material laser frequency doubling crystal and preparation method and application thereof Download PDFInfo
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- CN116706660A CN116706660A CN202310705601.1A CN202310705601A CN116706660A CN 116706660 A CN116706660 A CN 116706660A CN 202310705601 A CN202310705601 A CN 202310705601A CN 116706660 A CN116706660 A CN 116706660A
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- nonlinear optical
- refractive index
- optical crystal
- frequency doubling
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- 239000013078 crystal Substances 0.000 title claims abstract description 79
- 239000000463 material Substances 0.000 title claims abstract description 68
- 238000002360 preparation method Methods 0.000 title claims abstract description 8
- 230000003287 optical effect Effects 0.000 claims abstract description 33
- 230000000737 periodic effect Effects 0.000 claims abstract description 20
- 238000000034 method Methods 0.000 claims description 18
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 239000007788 liquid Substances 0.000 claims description 6
- 239000011521 glass Substances 0.000 claims description 4
- 239000011344 liquid material Substances 0.000 claims description 4
- 239000011343 solid material Substances 0.000 claims description 4
- 239000012530 fluid Substances 0.000 claims description 3
- 239000002178 crystalline material Substances 0.000 claims description 2
- -1 polymethylsiloxane Polymers 0.000 claims description 2
- 239000010453 quartz Substances 0.000 claims description 2
- 239000011347 resin Substances 0.000 claims description 2
- 229920005989 resin Polymers 0.000 claims description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 2
- 238000000992 sputter etching Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000000758 substrate Substances 0.000 abstract description 12
- 230000001276 controlling effect Effects 0.000 abstract description 3
- 230000001105 regulatory effect Effects 0.000 abstract description 3
- 235000019796 monopotassium phosphate Nutrition 0.000 description 6
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 238000007493 shaping process Methods 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- QBLDFAIABQKINO-UHFFFAOYSA-N barium borate Chemical compound [Ba+2].[O-]B=O.[O-]B=O QBLDFAIABQKINO-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 229920006026 co-polymeric resin Polymers 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- VCZFPTGOQQOZGI-UHFFFAOYSA-N lithium bis(oxoboranyloxy)borinate Chemical compound [Li+].[O-]B(OB=O)OB=O VCZFPTGOQQOZGI-UHFFFAOYSA-N 0.000 description 1
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910000402 monopotassium phosphate Inorganic materials 0.000 description 1
- PJNZPQUBCPKICU-UHFFFAOYSA-N phosphoric acid;potassium Chemical compound [K].OP(O)(O)=O PJNZPQUBCPKICU-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
- H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
- H01S3/109—Frequency multiplication, e.g. harmonic generation
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Nonlinear Science (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Optics & Photonics (AREA)
- Lasers (AREA)
Abstract
The application discloses a dual-material laser frequency doubling crystal and a preparation method and application thereof. The dual-material laser frequency doubling crystal comprises a nonlinear optical crystal and an index matching material; the surface of the nonlinear optical crystal is provided with a periodic groove, and the refractive index matching material is arranged in the periodic groove. According to the application, the nonlinear optical crystal is selected as the substrate material, the periodic structure with a smooth and steep interface is dug on the surface of the crystal, then the refractive index matching material is filled in the removing area of the substrate material for matching the refractive index of the frequency doubling light in the substrate material of the crystal, and the frequency doubling laser output working in the transparent wavelength range of the substrate material is realized by accurately regulating and controlling the lengths of the non-removing area and the removed area of the substrate material in a single period.
Description
Technical Field
The application relates to a dual-material laser frequency doubling crystal, a preparation method and application thereof, and belongs to the technical field of lasers.
Background
Nonlinear frequency conversion of laser is an important technique for expanding the wavelength of laser. The traditional technology utilizes the double refraction effect of the nonlinear optical crystal to realize the phase matching between the fundamental frequency light and the variable frequency light, so as to obtain the high-efficiency variable frequency laser. However, most of crystals in nature can realize the limited wavelength range of laser frequency conversion through the birefringence condition or have no birefringence characteristic at all, so that the nonlinear frequency conversion of laser, especially the nonlinear frequency conversion of deep ultraviolet band, is limited.
Disclosure of Invention
The application provides a material capable of realizing laser frequency multiplication, which is characterized in that a nonlinear optical crystal material is used as a substrate material by a method for carrying out phase matching on the nonlinear optical crystal material, a periodic structure with a smooth and steep interface is carved on the surface of the substrate material, then a removing area of the substrate material is filled with an index matching material for matching the refractive index of frequency multiplication light in the crystal substrate material, and frequency multiplication laser output working in a transparent wavelength range of the substrate material is realized by accurately regulating and controlling a period parameter, wherein the period parameter is the length of an area of the substrate material which is not removed and an area which is removed in a single period.
According to one aspect of the present application, there is provided a method for preparing a dual-material laser frequency doubling crystal, comprising the steps of:
a) Processing the surface of the nonlinear optical crystal in the crystal axis direction of the nonlinear optical crystal to obtain the nonlinear optical crystal with periodic grooves on the surface, wherein the single period length of the periodic grooves is lambada=L a +L b Wherein L is a Length of unprocessed region, L b Is the length of the area to be processed, as shown in fig. 2;
b) Filling refractive index matching materials into the periodic grooves of the nonlinear optical crystal processed in the step a) to obtain the double-material laser frequency doubling crystal.
The phase difference phi between the fundamental frequency light and the frequency doubling light in a single period of the nonlinear optical crystal filled in the step b) is as follows:
φ＝φ a +φ b ＝2Nπ；
wherein phi is a Length L of unprocessed region a Providing a phase difference between the fundamental frequency light and the frequency doubling light;
φ b length L of the area to be processed b Providing a phase difference between the fundamental frequency light and the frequency doubling light;
n is a non-negative integer.
The length L of the unprocessed region a The method meets the following conditions:
φ a ＝Δk a L a ＝2π(2n 1 /λ 1 -n 2 /λ 2 )L a ＝(2m+1)π；
wherein Δk is a The phase mismatch lattice inversion amount of the unprocessed area;
λ 1 is the fundamental wavelength;
λ 2 is the frequency multiplication wavelength;
n 1 refractive index of fundamental wavelength in nonlinear optical crystal;
n 2 refractive index in nonlinear optical crystal for frequency multiplication wavelength;
m is a non-negative integer.
Length of the region to be processed L b The method meets the following conditions:
φ b ＝Δk b L b ＝2π(2n’ 1 /λ 1 -n’ 2 /λ 2 )L b ＝(2n+1)π；
wherein Δk is b The phase mismatch lattice inversion amount in the refractive index matching material;
n’ 1 refractive index in the index matching material for fundamental wavelength;
n’ 2 for doubling the wavelength at refractive indexRefractive index in the formulation;
n is a non-negative integer.
Optionally, the nonlinear optical crystal has non-central inversion symmetry.
Optionally, the nonlinear optical crystal is selected from at least one of BBO, LBO, LN, KDP and quartz.
Optionally, the index matching material comprises a liquid material and a solid material;
the liquid material is at least one selected from refractive index matching liquid and resin;
the solid material is at least one selected from photosensitive materials, polymethylsiloxane, glass and crystal materials.
Optionally, the refractive index of the refractive index matching fluid is 1.5-1.85.
Optionally, the glass is grown in periodic grooves of a nonlinear optical crystal based on epitaxial techniques.
Optionally, the crystalline material is grown in periodic grooves of a nonlinear optical crystal based on epitaxial techniques.
Optionally, in step a), the machining mode is a laser machining or ion etching process.
In the present application, "BBO" means beta-phase barium metaborate;
"LBO" means lithium triborate;
"LN" refers to lithium niobate;
"KDP" refers to potassium dihydrogen phosphate.
According to yet another aspect of the present application, there is provided a dual-material laser frequency doubling crystal comprising a nonlinear optical crystal and an index matching material;
the surface of the nonlinear optical crystal is provided with a periodic groove, and the refractive index matching material is arranged in the periodic groove.
According to still another aspect of the application, there is provided an application of a dual-material laser frequency doubling crystal in deep ultraviolet band nonlinear frequency conversion.
The application has the beneficial effects that:
1) The preparation method provided by the application selects the crystal axis of the nonlinear crystal as the light transmission direction, can obtain the maximum effective nonlinear coefficient, and overcomes the defects that the crystal cutting direction needs to be strictly controlled in the main flow birefringence phase matching and the ultraviolet frequency doubling wavelength cannot be further expanded in the crystal transparent wavelength range due to the restriction of the birefringence condition.
2) The preparation method provided by the application provides the degree of freedom of refractive index regulation, and the high-power frequency multiplication output is realized by accurately regulating the lengths of the non-removed area and the removed area of the substrate material in a single period and filling the grooves of the nonlinear crystal material with the refractive index matching material, wherein the refractive index matching material is selected from the loss of the matchable frequency multiplication light in the periodic grooves.
3) The dual-material laser frequency doubling crystal provided by the application can realize deep ultraviolet band frequency conversion.
Drawings
FIG. 1 is a schematic diagram of a dual-material laser frequency doubling crystal according to the present application;
FIG. 2 is a top view of a dual-material laser frequency doubling crystal according to the present application;
FIG. 3 is a schematic diagram of laser frequency multiplication based on a dual-material laser frequency multiplication crystal according to the present application.
10. A dual-material laser frequency doubling crystal 11 and a nonlinear optical crystal. 12. 13 parts of refractive index matching materials, 20 parts of frequency multiplication lasers, 21 parts of fundamental frequency laser sources, 22 parts of laser shaping systems, 23 parts of dichroic lenses and 23 parts of fundamental frequency lasers.
Detailed Description
The present application is described in detail below with reference to examples, but the present application is not limited to these examples.
Unless otherwise indicated, materials in the examples of the present application were purchased commercially.
To achieve the frequency-doubled laser output from the prepared dual-material laser frequency-doubling crystal, the measurement is performed using the schematic diagram as described in fig. 3, using a fundamental laser source 20, collimating the fundamental laser 23 by a laser shaping system 21 and controlling the incident light spot within the light-passing size range of the dual-material laser frequency crystal 10, and using a dichroic mirror 22 to separate the residual fundamental laser 23 from the frequency-doubled laser 13.
Example 1
LBO crystal is selected as a base material to realize 340nm to 170nm frequency multiplication output;
to obtain the maximum nonlinear coefficient d from the crystal 31 The X-axis of the crystal is selected as the light-transmitting direction, and the polarization direction of the fundamental frequency light and the frequency doubling light is controlled along the Z-axis of the crystal, so that phi is formed a ＝Δk a L a ＝2π|(2n 1 /λ 1 -n 2 /λ 2 )|L a =5pi, where n 1 ＝1.629，n 2 = 1.812, give L a ＝2.32μm；
The refractive index matching liquid working in the deep ultraviolet band is selected, and the refractive index matching liquid is copolymer resin, so that the refractive index matching liquid is matched with the refractive index of LBO crystal in the Z-axis direction of 170nm, and is marked as n' 2 = 1.8138 and the refractive index of the index matching fluid at 340nm wavelength is measured and obtained and is denoted as n' 1 = 1.5103, according to formula 2pi (2n' 1 /λ 1 -n’ 2 /λ 2 )L b ＝(2n+1)π，φ b Calculate the length L of the material displaced area =7pi b ＝1.96μm。
Preparing L on the surface of LBO crystal by femtosecond laser processing technology b And L a The periodic structure of alternate distribution is excavated to a depth depending on the frequency doubling laser spot size, and refractive index matching liquid is injected for filling, as shown in fig. 1. And a 340nm femtosecond laser generated by triple frequency of a tunable Ti-doped sapphire laser is used as a fundamental frequency light source, and fundamental frequency light is injected into a designed bi-material periodic structure based on LBO and refractive index matching combination in a shaping way, so that deep ultraviolet 170nm double frequency laser output is generated.
Example 2
KDP crystal is selected as a base material, and 1064nm laser lambda is developed 1 And 532nm frequency doubling light lambda 2 3 times 355nm laser lambda 3 Experimental study.
The cutting direction of the fixed KDP crystal is θ=45°,i.e. the light passing direction is at 45 deg. to the main crystal axis to obtain the maximum non-linear coefficient d 14 . The 1064nm nanosecond laser is adopted to carry out frequency doubling through the PPLN crystal, the 1064nm laser and 532nm frequency doubling light with the same polarization direction residues are used as o light to be injected into the dual-material laser frequency doubling crystal together, and the corresponding refractive indexes are n respectively 1 =1.494 and n 2 Refractive index n of sum frequency light 354.7nm (e light) =1.512 3 =1.508. Let phia=Δk a L a ＝2π(n 3 /λ 3 -n 1 /λ 1 -n 2 /λ 2 )L a Pi, give L a = 95.43 μm; dimethyl sulfoxide DMSO is used as an index matching material to match the index of refraction of the KDP crystal in 355nm bands, wherein the index of refraction in 1064nm,532nm and 354.7nm bands is n' 1 ＝1.475，n’ 2 = 1.481 and n' 3 = 1.509, let φ b ＝Δk b L b ＝2π(n 3 /λ 3 -n 1 /λ 1 -n 2 /λ 2 )L b Pi, give L b =5.94 μm; the dual-material laser frequency doubling crystal with 200 periods and the total length of approximately 20mm is prepared, and the frequency tripling output of 1064nm laser is realized.
While the application has been described in terms of preferred embodiments, it will be understood by those skilled in the art that various changes and modifications can be made without departing from the scope of the application, and it is intended that the application is not limited to the specific embodiments disclosed.
Claims (10)
1. The preparation method of the dual-material laser frequency doubling crystal is characterized by comprising the following steps of:
a) Processing the surface of the nonlinear optical crystal in the crystal axis direction of the nonlinear optical crystal to obtain the nonlinear optical crystal with periodic grooves on the surfaceIs of single period length Λ=l a +L b Wherein L is a Length of unprocessed region, L b Is the length of the area to be processed;
b) Filling refractive index matching materials into the periodic grooves of the nonlinear optical crystal processed in the step a) to obtain a double-material laser frequency doubling crystal;
the phase difference phi between the fundamental frequency light and the frequency doubling light in a single period of the nonlinear optical crystal filled in the step b) is as follows:
φ＝φ a +φ b ＝2Nπ；
wherein phi is a Length L of unprocessed region a Providing a phase difference between the fundamental frequency light and the frequency doubling light;
φ b length L of the area to be processed b Providing a phase difference between the fundamental frequency light and the frequency doubling light;
n is a non-negative integer;
the length L of the unprocessed region a The method meets the following conditions:
φ a ＝Δk a L a ＝2π(2n 1 /λ 1 -n 2 /λ 2 )L a ＝(2m+1)π；
wherein Δk is a The phase mismatch lattice inversion amount of the unprocessed area;
λ 1 is the fundamental wavelength;
λ 2 is the frequency multiplication wavelength;
n 1 refractive index of fundamental wavelength in nonlinear optical crystal;
n 2 refractive index in nonlinear optical crystal for frequency multiplication wavelength;
m is a non-negative integer;
length of the region to be processed L b The method meets the following conditions:
φ b ＝ΔkbL b ＝2π(2n’ 1 /λ 1 -n’ 2 /λ 2 )L b ＝(2n+1)π；
wherein Δk is b The phase mismatch lattice inversion amount in the refractive index matching material;
n’ 1 index matching material for fundamental wavelengthRefractive index of (a);
n’ 2 refractive index in the refractive index matching material for the frequency doubling wavelength;
n is a non-negative integer.
2. The method of claim 1, wherein the nonlinear optical crystal has non-central inversion symmetry.
3. The method according to claim 2, wherein the nonlinear optical crystal is at least one selected from BBO, LBO, LN, KDP and quartz.
4. The method of manufacturing according to claim 1, wherein the index matching material comprises a liquid material and a solid material;
the liquid material is at least one selected from refractive index matching liquid and resin;
the solid material is at least one selected from photosensitive materials, polymethylsiloxane, glass and crystal materials.
5. The method according to claim 4, wherein the refractive index of the refractive index matching fluid is 1.5 to 1.85.
6. The method of claim 4, wherein the glass is grown in periodic grooves of a nonlinear optical crystal based on epitaxial techniques.
7. The method of claim 4, wherein the crystalline material is grown in periodic grooves of a nonlinear optical crystal based on epitaxial techniques.
8. The method according to claim 1, wherein in step a), the processing is performed by laser processing or ion etching.
9. A dual-material laser frequency doubling crystal obtained by the preparation method according to any one of claims 1 to 8, comprising a nonlinear optical crystal and an index matching material;
the surface of the nonlinear optical crystal is provided with a periodic groove, and the refractive index matching material is arranged in the periodic groove.
10. An application of the dual-material laser frequency doubling crystal in deep ultraviolet band nonlinear frequency conversion.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202310705601.1A CN116706660A (en) | 2023-06-14 | 2023-06-14 | Dual-material laser frequency doubling crystal and preparation method and application thereof |
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| CN202310705601.1A CN116706660A (en) | 2023-06-14 | 2023-06-14 | Dual-material laser frequency doubling crystal and preparation method and application thereof |
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