CN110535020B - Optical parametric oscillator for welding transparent or white plastics - Google Patents

Optical parametric oscillator for welding transparent or white plastics Download PDF

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CN110535020B
CN110535020B CN201910846149.4A CN201910846149A CN110535020B CN 110535020 B CN110535020 B CN 110535020B CN 201910846149 A CN201910846149 A CN 201910846149A CN 110535020 B CN110535020 B CN 110535020B
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laser
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CN110535020A (en
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张百涛
聂鸿坤
颜秉政
刘俊亭
杨克建
何京良
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Shandong Birui Laser Technology Co ltd
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Shandong 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
    • H01S3/09—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
    • H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
    • 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
    • H01S3/102—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
    • H01S3/1028—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation by controlling the temperature
    • 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
    • H01S3/105—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the mutual position or the reflecting properties of the reflectors of the cavity, e.g. by controlling the cavity length
    • 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
    • H01S3/1083—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 using parametric generation
    • 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
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/163—Solid materials characterised by a crystal matrix
    • H01S3/1671—Solid materials characterised by a crystal matrix vanadate, niobate, tantalate
    • 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
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/163—Solid materials characterised by a crystal matrix
    • H01S3/1675—Solid materials characterised by a crystal matrix titanate, germanate, molybdate, tungstate

Abstract

The invention relates to an optical parametric oscillator for welding transparent or white plastics, which comprises a semiconductor laser A, a collimation focusing system A, a resonant cavity and a filter plate, wherein the semiconductor laser A, the collimation focusing system A, the resonant cavity and the filter plate are sequentially arranged along a light path; the resonant cavity comprises a laser input mirror, a nonlinear optical crystal and a laser output mirror; the nonlinear optical crystal is a periodically polarized optical superlattice crystal, the period of the optical superlattice crystal is 20-30 μm, and the temperature of the optical superlattice crystal is controlled at 50-200 deg.C. The invention can realize the simultaneous output of 1710nm and 2300nm lasers, and can greatly improve the absorption efficiency of transparent or white plastic materials; high power can be realized by optimizing the resonant cavity structure of the optical parametric oscillator>50W), high efficiency, high beam quality (M)2<1.5) and 2300nm laser are simultaneously output, and the requirement of laser welding of transparent or white plastics is met.

Description

Optical parametric oscillator for welding transparent or white plastics
Technical Field
The invention relates to an optical parametric oscillator for welding transparent or white plastics, belonging to the technical field of solid-state laser.
Background
Laser has the advantages of good directivity, high brightness, good monochromaticity and the like, so the laser is widely applied to the field of industrial processing. The laser processing technology is one of the main applications of the laser technology in the industry, accelerates the reconstruction of the traditional processing industry, and provides a new means for the modern processing technology. The laser processing is cutting, scribing, marking, welding, punching, and the like of an industrial component by a laser beam. Compared with the traditional method, the laser processing has the advantages of good processing quality, high processing speed, high precision, no limit of the processing piece on size and shape, no pollution, low noise, no tool abrasion, high efficiency and the like.
Since the 21 st century, the rapid development of laser technology provides more technical schemes for plastic welding, so that the average efficiency of plastic welding is 2-3 times higher than that of the traditional welding process. Therefore, the laser plastic welding technology becomes a novel laser processing technology which is rapidly developed in recent years, the share of the whole plastic welding processing market is continuously increased, and particularly, the laser plastic welding technology has clear characteristics and obvious advantages in some occasions requiring high welding efficiency and strict appearance requirements. When the plastic welding is carried out, the two parts are clamped together, the upper-layer plastic welding part has high transmittance to laser, and the lower-layer plastic welding part has high absorption rate to the laser. The laser beam penetrates through the upper layer of plastic to irradiate the surface of the lower layer of welding part, the lower layer of plastic absorbs laser energy and is converted into heat energy, then the contact surface of the two layers of plastic is melted to form a welding area, and the two layers of plastic are combined together after being cooled to finish the welding process. Laser welding of plastics has been widely adopted in the welding of plastic appliances for medical use, plastic parts for white home appliances, and plastic parts for automobiles. Commonly used welding light sources are semiconductor lasers (wavelength 808nm or 980nm), Nd: YAG all-solid-state lasers or fiber lasers (wavelength around 1.0 micron). However, when both parts are made of transparent materials, the conventional method is difficult to perform laser welding by using the working principle: since transparent materials generally have a very low absorption of visible light, this results in the case of only the transmissive layer and the absence of the absorptive layer. Therefore, the need to make an absorber on the surface of the absorbing layer increases the light absorption, which also causes contamination of the plastic work piece, limiting its application in transparent plastic welding, such as for medical use.
As can be seen from the infrared laser absorption spectrum (fig. 1) of common plastics, the light absorption rate of most plastic materials to the wavelengths of 1710nm and 2300nm exceeds 70% or even 80-90%, which is very beneficial to the laser tailor welding of plastic products with various thicknesses and the laser penetration welding of transparent plastic sheets with the thickness of less than 1.5mm, has passed many practical verifications in the laser welding of medical plastic appliances, plastic parts of white appliances and plastic parts of automobiles, and is beginning to be applied to a series of laser plastic welding equipment to carry out the formal production of some plastic part products, with good effect, and is gradually accepted by the plastic laser welding industry. By utilizing the characteristic of intrinsic absorption of the polymer near 1710nm and 2300nm wave bands, the transparent material can be welded without an absorption layer, the requirement of an additive for manufacturing the absorption layer is eliminated, and the processing quality is also very excellent.
To date, the lasers used for many welds of transparent and white plastics have been primarily 1710nm semiconductor lasers and 2000nm fiber lasers. The 1710nm semiconductor laser has poor beam quality and output power far lower than those of 808nm and 976nm semiconductor lasers; 2000nm fiber lasers are good but costly, and the absorption of plastics in this band is also less than 2300nm (as depicted in figure 1). The existing optical parametric oscillator pumping sources are mature all-solid-state lasers with the wavelength of 1 micron wave band, nonlinear crystals are bulk single crystals (potassium dihydrogen phosphate KTP, zinc germanium phosphate ZGP and the like), and phase matching cannot be realized when 1710nm and 2300nm are simultaneously output according to an optical parametric oscillation three-wave coupling equation. Therefore, the simultaneous output of 1710nm and 2300nm is difficult to realize by adopting the refractive index phase matching technology of bulk single crystal; further, no report has been made so far on simultaneous output at 1710nm and 2300 nm.
Disclosure of Invention
In view of the deficiencies of the prior art, the present invention provides an optical parametric oscillator for transparent or white plastic welding.
The invention adopts semiconductor laser pumping nonlinear optical crystal to generate optical parametric oscillation, and realizes the simultaneous output of high power>50W), high efficiency, high beam quality (M)2<1.5) of 1710nm and 2300nm, and meets the requirements of laser welding of transparent or white plastics.
The technical scheme of the invention is as follows:
an optical parametric oscillator for welding transparent or white plastics comprises a semiconductor laser A, a collimation focusing system A, a resonant cavity and a filter plate which are sequentially arranged along a light path; the resonant cavity comprises a laser input mirror, a nonlinear optical crystal and a laser output mirror;
the nonlinear optical crystal is a periodically polarized optical superlattice crystal, the period of the optical superlattice crystal is 20-30 mu m, and the temperature of the optical superlattice crystal is controlled at 50-200 ℃; the working wavelength of the semiconductor laser A is 800-1000 nm;
after the pump light output by the semiconductor laser A is collimated by the collimating and focusing system A, the pump light is incident into the resonant cavity, the pump light is incident onto the nonlinear optical crystal after passing through the laser input mirror, the nonlinear optical crystal is pumped, optical oscillation is formed in the resonant cavity, signal light and idle frequency light are generated, and the signal light and the idle frequency light are coupled and output by the laser output mirror; the filter filters laser with other wavelengths and outputs laser with 1710nm and 2300nm wavelengths.
The working principle of the optical parametric oscillator provided by the invention is as follows: the optical parametric oscillator makes the incident frequency omegapThe pump light is converted into two output lights (signal light omega) with lower frequencies through the second-order nonlinear optical action of the nonlinear optical crystalsAnd idler light omegai) The sum of the frequencies of the two output lights is equal to the incident light frequency: omegap＝ωs+ωi. In the nonlinear optical crystal, pump light, signal light and idler frequency light are superposed with each other, three-wave interaction causes the signal light and the idler frequency light to oscillate in a resonant cavity and be amplified continuously, and when gain is larger than loss, the signal light and the idler frequency light are output.
In the phase matching, the phase mismatch generated by the three-wave coupling process is compensated by the reciprocal lattice vector generated by the polarization, that is: k isp-ks-k i2 pi/Λ denotes the period of the optical superlattice crystal, kpIs the pumping light wave vector, ksIs the signal light wave vector, kiIs the idler wave vector, and delta k is the amount of the pump light, the signal light and the idler wave vector mismatch; by designing the wavelength of the corresponding pump light and the period of the optical superlattice crystal and compensating the mismatch generated by the crystal property through electric field polarization, the parametric light output with the wavelengths of 1710nm and 2300nm can be realized;
in the process of satisfying phase matching, energy conservation and momentum conservation of three waves must be satisfied, that is:
1/λp＝1/λs+1/λi(Ⅰ)，λpdenotes the wavelength, λ, of the pump lightsIndicating the wavelength, λ, of the signal lightiRepresents the wavelength of the idler light;
np/λp＝ns/λs+ni/λi(Ⅱ)，nprespectively the refractive index of the pump light, nsRefractive index of signal light, niThe refractive index of the idler light;
obtained from the formulae (I) and (II): lambda [ alpha ]i＝(ni-ns)λp/(np-ns) (III) changing refractive indexes of the pump light, the signal light and the idler light by changing temperature. In the invention, wavelength tuning is realized by changing the polarization period of the crystal and controlling the temperature of the crystal, and continuous tuning output of the signal light and the idler frequency light can be realized by combining the two modes.
According to the invention, the period of the optical superlattice crystal is 29 μm, the temperature of the optical crystal is controlled at 134 ℃, and the operating wavelength of the semiconductor laser A is 808nm or 980 nm; preferably, the operating wavelength of the semiconductor laser A is 980 nm. The pump light is ensured to have higher power, and the optical parametric oscillation is ensured to have higher quantum efficiency; the continuous tunable output of 1710nm and 2300nm wavelength can be realized by the common regulation and control of the pumping wavelength, the period of the optical superlattice crystal and the temperature.
Preferably, according to the present invention, the optical superlattice crystal is any one of a periodically poled lithium niobate crystal (PPLN), a periodically poled potassium titanyl phosphate crystal (PPKTP), a periodically poled lithium tantalate crystal (PPLT), a periodically poled homomorphic lithium niobate crystal (PPCLN), and a periodically poled homomorphic lithium tantalate crystal (PPCLT).
According to the present invention, preferably, the optical parametric oscillator further includes a semiconductor laser B and a collimating and focusing system B, and the resonant cavity further includes a 45 ° harmonic mirror a; the semiconductor laser B, the collimation focusing system B, the 45-degree harmonic mirror A and the nonlinear optical crystal are sequentially arranged along a light path, the 45-degree harmonic mirror A and the light path form a 45-degree included angle, the laser output mirror is arranged on one side of the 45-degree harmonic mirror A and is perpendicular to the light path, and the working wavelength of the semiconductor laser B is 800-1000 nm; preferably, the operating wavelength of the semiconductor laser B is 808nm or 980 nm.
After the pump light output by the semiconductor laser A is collimated by the collimating and focusing system A, the pump light is incident into the resonant cavity, and the pump light is incident onto the nonlinear optical crystal after passing through the laser input mirror to pump the nonlinear optical crystal; simultaneously, the pump light of semiconductor laser B output passes through behind collimation focusing system B's the collimation, the pump light incides in the resonant cavity, the pump light passes through incidenting behind 45 harmonic mirror A on the nonlinear optical crystal, 45 harmonic mirror A is highly anti-to pump light high-transparent oscillation light (signal light and idle frequency light), and semiconductor laser A and semiconductor laser B are right simultaneously nonlinear optical crystal carries out the pumping and forms optical oscillation in the resonant cavity, produces signal light and idle frequency light to by laser output mirror coupling output, the laser of other wavelength is filtered out to the filter plate, the laser of output 1710nm and 2300nm wavelength. The double-end pumping structure can relieve the heat effect of the nonlinear crystal and improve the conversion efficiency and the output power. 45 harmonic mirror A is high to pump light and is high anti-to signal light and idle frequency light, through 45 harmonic mirror A and laser output mirror's cooperation, can optimize the size of intracavity oscillation facula, realizes the mode matching of pump light and oscillation light, improves the light beam quality of the 1710nm of output and 2300nm laser.
According to the present invention, preferably, the resonant cavity further includes a 45 ° harmonic mirror B, the 45 ° harmonic mirror B is disposed between the collimating and focusing system a and the nonlinear optical crystal, and the 45 ° harmonic mirror B forms a 45 ° included angle with the optical path; the laser input mirror is arranged on one side of the 45-degree harmonic mirror B and is perpendicular to the light path.
After being collimated by the collimating and focusing system A, the pump light output by the semiconductor laser A is incident into the resonant cavity, and after passing through the 45-degree harmonic mirror B, the pump light is incident onto the nonlinear optical crystal to pump the nonlinear optical crystal; meanwhile, pump light output by the semiconductor laser B is incident into the resonant cavity after being collimated by the collimating and focusing system B, passes through the 45-degree harmonic mirror A and then is incident onto the nonlinear optical crystal, and the 45-degree harmonic mirror B highly reflects pump light high-transmittance oscillation light (signal light and idler frequency light), so that the semiconductor laser A and the semiconductor laser B simultaneously pump the nonlinear optical crystal to form light oscillation in the resonant cavity, generate the signal light and the idler frequency light, and are coupled and output by the laser output mirror. 45 harmonic mirror B is high to pump light and passes through, and is high anti to signal light and idle frequency light, through 45 harmonic mirror B and laser input mirror's cooperation, can optimize the size of intracavity oscillation facula, realizes the mode matching of pump light and oscillation light, improves the light beam quality of the 1710nm of output and 2300nm laser.
According to the invention, the laser input mirror and the laser output mirror are preferably made of calcium fluoride crystal, mid-infrared quartz or ZnSe crystal. The calcium fluoride crystal, the mid-infrared quartz crystal and the ZnSe crystal have the transmission effect on idler frequency light of 2300nm and 1700nm positioned in a mid-infrared band, and the positive feedback and the mode selection of the resonant cavity are realized.
According to the invention, the angle a between the filter plate and the light path preferably satisfies: a is more than 10 degrees and less than 45 degrees.
According to the invention, the laser input mirror and the laser output mirror are preferably plated with dielectric films, the laser input mirror is plated with a pumping light antireflection film and high reflection films with the wavelengths of 1710nm and 2300nm, and the laser output mirror is plated with partial transmission films with the wavelengths of 1710nm and 2300 nm.
According to the invention, the output modes of the semiconductor laser A and the semiconductor laser B are both one of free space direct output, optical fiber coupling output, stack output and linear array output modes.
According to the invention, the collimation focusing system A and the collimation focusing system B both comprise two lenses and a waveguide element, the two lenses are arranged in parallel relatively, and the waveguide element is arranged between the two lenses. When the output mode of the semiconductor laser is a stack or linear array output mode, the waveguide element can make the pump light more uniform.
The invention has the beneficial effects that:
1) the invention converts mature 800-plus-1000 nm semiconductor laser into 1710nm and 2300nm wave bands with larger absorption of transparent or white plastic by pumping the optical superlattice crystal through the semiconductor laser, and realizes the optical parametric oscillator which simultaneously outputs 1710nm and 2300nm, thereby having high efficiency and good beam quality.
2) The invention can realize the simultaneous output of 1710nm and 2300nm lasers and can greatly improve the absorption efficiency of transparent or white plastic materials.
3) The continuous tuning output of the signal light and the idler frequency light can be realized by adjusting the period and the temperature of the optical superlattice crystal, so that different wavelength outputs can be selected for different plastic materials.
4) At present, an optical parametric oscillator for realizing 1710nm and 2300nm simultaneous output is not reported, and high power is realized by optimizing a resonant cavity structure of the optical parametric oscillator>50W), high efficiency, high beam quality (M)2<1.5) and 2300nm laser are simultaneously output, and the requirement of laser welding of transparent or white plastics is met.
Drawings
FIG. 1 absorption transmission lines of a conventional plastic;
fig. 2 is a schematic structural diagram of an optical parametric oscillator provided in embodiment 1 of the present invention;
fig. 3 is a schematic structural diagram of an optical parametric oscillator provided in embodiment 3 of the present invention;
fig. 4 is a schematic structural diagram of an optical parametric oscillator provided in embodiment 4 of the present invention;
1. the laser system comprises semiconductor lasers A, 2, collimation focusing systems A, 3, a laser input mirror, 4, a nonlinear optical crystal, 5, a laser output mirror, 6, a filter, harmonic mirrors A, 8 of 7 and 45 degrees, collimation focusing systems B, 9 and semiconductor lasers B, 10 and 45 degrees.
Detailed Description
The invention is further described below, but not limited thereto, with reference to the following examples and the accompanying drawings.
Example 1
An optical parametric oscillator for welding transparent or white plastics, as shown in fig. 2, comprises a semiconductor laser A1, a collimation focusing system A2, a resonant cavity and a filter 6 which are arranged along a light path in sequence; the resonant cavity comprises a laser input mirror 3, a nonlinear optical crystal 4 and a laser output mirror 5;
in this embodiment, the period of the optical superlattice crystal is 29 μm, the temperature of the optical superlattice crystal is controlled at 134 ℃, and the operating wavelength of the semiconductor laser a1 is 980 nm.
The optical superlattice crystal is a periodically poled potassium titanyl phosphate crystal (PPKTP).
After being collimated by a collimating and focusing system A2, pump light output by a semiconductor laser A1 is incident into a resonant cavity, passes through a laser input mirror 3 and is incident onto a nonlinear optical crystal 4, the nonlinear optical crystal 4 is pumped, optical oscillation is formed in the resonant cavity, signal light and idler frequency light are generated, and the signal light and the idler frequency light are coupled and output by a laser output mirror 5; the filter 6 filters out laser beams with other wavelengths and outputs laser beams with 1710nm and 2300nm wavelengths.
The working principle of the optical parametric oscillator provided by the invention is as follows: the optical parametric oscillator makes the incident frequency omegapThe pump light of (2) is converted into two output lights (signal light omega) with lower frequencies by the second-order nonlinear optical action of the nonlinear optical crystal 4sAnd idler light omegai) The sum of the frequencies of the two output lights is equal to the incident light frequency: omegap＝ωs+ωi. In the nonlinear optical crystal 4, the pump light, the signal light and the idler frequency light are superposed with each other, the signal light and the idler frequency light are oscillated and amplified continuously in the resonant cavity due to interaction of the three waves, and the signal light and the idler frequency light are output when the gain is larger than the loss.
In the phase matching, the phase mismatch generated by the three-wave coupling process is compensated by the reciprocal lattice vector generated by the polarization, that is: k isp-ks-k i2 pi/Λ denotes the period of the optical superlattice crystal, kpIs the pumping light wave vector, ksIs the signal light wave vector, kiIs the idler wave vector, and delta k is the amount of the pump light, the signal light and the idler wave vector mismatch;by designing the wavelength of the corresponding pump light and the period of the optical superlattice crystal and compensating the mismatch generated by the crystal property through electric field polarization, the parametric light output with the wavelengths of 1710nm and 2300nm can be realized;
in the process of satisfying phase matching, energy conservation and momentum conservation of three waves must be satisfied, that is:
1/λp＝1/λs+1/λi(Ⅰ)，λpdenotes the wavelength, λ, of the pump lightsIndicating the wavelength, λ, of the signal lightiRepresents the wavelength of the idler light;
np/λp＝ns/λs+ni/λi(Ⅱ)，nprespectively the refractive index of the pump light, nsRefractive index of signal light, niThe refractive index of the idler light;
obtained from the formulae (I) and (II): lambda [ alpha ]i＝(ni-ns)λp/(np-ns) (III) changing refractive indexes of the pump light, the signal light and the idler light by changing temperature. In the invention, wavelength tuning is realized by changing the polarization period of the crystal and controlling the temperature of the crystal, and continuous tuning output of the signal light and the idler frequency light can be realized by combining the two modes.
The optical superlattice crystal is placed in a temperature control furnace, the temperature control furnace is a device for controlling/adjusting the temperature of the nonlinear optical crystal 4, and the temperature of the crystal is controlled by controlling the current of the temperature control furnace; and also as a fixture for the nonlinear optical crystal 4, the temperature controlled furnace is not shown in the figure.
The mode of realizing wavelength tuning by changing the refractive index of light waves through temperature is widely applied to various phase matching, and the temperature tuning is simpler and easier to obtain due to the sheet structure of the optical superlattice crystal. In the invention, wavelength tuning is realized by changing the polarization period of the crystal and controlling the temperature of the crystal, and continuous tuning output of the optical wavelengths of the signal light and the idler can be realized by combining the two modes.
The materials of the laser input mirror 3 and the laser output mirror 5 are calcium fluoride crystals. The calcium fluoride crystal has a transmission effect on idler frequency light of 2300nm and 1700nm in a middle infrared band, and the positive feedback and mode selection effects of the resonant cavity are realized.
The angle a of the filter 6 to the light path is 15.
The laser input mirror 3 and the laser output mirror 5 are plated with dielectric films, the laser input mirror 3 is plated with a pumping light antireflection film and high reflection films with the wavelengths of 1710nm and 2300nm, and the laser output mirror 5 is plated with a partial transmission film with the wavelengths of 1710nm and 2300 nm.
The output mode of the semiconductor laser a1 is free-space direct output.
Example 2
An optical parametric oscillator for transparent or white plastic welding is provided according to embodiment 1, with the difference that:
in this example, the operating wavelength of the semiconductor laser a1 is 808nm, the output mode of the semiconductor laser a1 is fiber-coupled output, and the angle a between the filter 6 and the optical path satisfies 30 °.
The laser input mirror 3 and the laser output mirror 5 are made of mid-infrared quartz. The mid-infrared quartz has a transmission effect on idler frequency light of 2300nm and 1700nm in a mid-infrared band, and achieves the functions of positive feedback and mode selection of the resonant cavity.
In this embodiment, the nonlinear optical crystal 4 is a periodically poled lithium niobate crystal (PPLN), the period of the nonlinear optical crystal 4 is 20 μm, and the temperature of the nonlinear optical crystal 4 is controlled at 200 ℃.
The single resonance can be realized by adjusting the temperature of the PPLN crystal, only the idler frequency light 2300nm wave band oscillates in the cavity, and the wavelength of 2300nm is output.
Example 3
An optical parametric oscillator for transparent or white plastic welding is provided according to embodiment 1, with the difference that:
as shown in fig. 3, the optical parametric oscillator further includes a semiconductor laser B9 and a collimating and focusing system B8, and the resonator further includes a 45 ° harmonic mirror a 7; the laser device comprises a semiconductor laser B9, a collimation and focusing system B8, a 45-degree harmonic mirror A7 and a nonlinear optical crystal 4 which are sequentially arranged along a light path, wherein the 45-degree harmonic mirror A7 forms a 45-degree included angle with the light path, a laser output mirror 5 is arranged on one side of the 45-degree harmonic mirror A7, the laser output mirror 5 is perpendicular to the light path, and the working wavelength of the semiconductor laser B9 is 808 nm.
The optical superlattice crystal is a periodically polarized lithium tantalate crystal (PPLT).
After being collimated by a collimating and focusing system A2, the pump light output by the semiconductor laser A1 is incident into the resonant cavity, passes through the laser input mirror 3 and is incident on the nonlinear optical crystal 4, and the nonlinear optical crystal 4 is pumped; meanwhile, after being collimated by a collimating and focusing system B8, pump light output by a semiconductor laser B9 enters a resonant cavity, the pump light enters a nonlinear optical crystal 4 after passing through a 45-degree harmonic mirror A7, the 45-degree harmonic mirror A7 highly reflects pump light high-transmittance oscillation light (signal light and idler frequency light), the semiconductor laser A1 and the semiconductor laser B9 simultaneously pump the nonlinear optical crystal 4 to form optical oscillation in the resonant cavity, the signal light and the idler frequency light are generated and are coupled and output by a laser output mirror 5, lasers with other wavelengths are filtered by a filter 6, and lasers with 1710nm and 2300nm wavelengths are output. The double-end pumping structure can relieve the heat effect of the nonlinear crystal and improve the conversion efficiency and the output power. The 45-degree harmonic mirror A7 has high transmission for pump light and high reflection for signal light and idler frequency light, and the size of an oscillation light spot in a cavity can be optimized through the matching of the 45-degree harmonic mirror A7 and the laser output mirror 5, so that the mode matching of the pump light and the oscillation light is realized, and the light beam quality of output 1710nm and 2300nm laser is improved.
The angle a of the filter 6 and the light path satisfies 45 °.
The materials of the laser input mirror 3 and the laser output mirror 5 are ZnSe crystals. The ZnSe crystal has a transmission effect on idler frequency light of 2300nm and 1700nm positioned in a middle infrared band, and the positive feedback and mode selection effects of the resonant cavity are realized.
The output mode of the semiconductor laser B9 is a stack output mode.
The collimating focusing system A2 and the collimating focusing system B8 both comprise two lenses and a waveguide element, the two lenses are arranged in parallel, the waveguide element is arranged between the two lenses, and the waveguide element can enable the pumping light to be more uniform.
Example 4
An optical parametric oscillator for transparent or white plastic welding is provided according to embodiment 3, with the difference that:
as shown in fig. 4, the optical superlattice crystal is a periodically poled homogeneous lithium niobate crystal (PPCLN), the period of the optical superlattice crystal is 20 μm, and the temperature of the optical superlattice crystal is controlled at 50 ℃.
The operating wavelength of the semiconductor laser B9 was 980nm, and the output mode of the semiconductor laser B was the line output mode.
The resonant cavity also comprises a 45-degree harmonic mirror B10, a 45-degree harmonic mirror B10 is arranged between the collimation focusing system A2 and the nonlinear optical crystal 4, and an included angle of 45 degrees is formed between the 45-degree harmonic mirror B10 and a light path; the laser input mirror 3 is disposed on one side of the 45 ° harmonic mirror B10, and the laser input mirror 3 is perpendicular to the optical path.
After being collimated by a collimating and focusing system A2, pump light output by a semiconductor laser A1 is incident into a resonant cavity, passes through a 45-degree harmonic mirror B10 and is incident onto a nonlinear optical crystal 4, and the nonlinear optical crystal 4 is pumped; meanwhile, after being collimated by a collimating and focusing system B8, pump light output by a semiconductor laser B9 is incident into a resonant cavity, the pump light is incident onto the nonlinear optical crystal 4 after passing through a 45-degree harmonic mirror A7, and the 45-degree harmonic mirror B10 highly reflects pump light high-transmittance oscillation light (signal light and idler frequency light), so that the semiconductor laser A1 and the semiconductor laser B9 simultaneously pump the nonlinear optical crystal 4 to form optical oscillation in the resonant cavity, generate the signal light and the idler frequency light, and are coupled and output by a laser output mirror 5. The 45-degree harmonic mirror B10 has high transmission for pump light and high reflection for signal light and idler frequency light, and the size of an oscillation light spot in a cavity can be optimized through the matching of the 45-degree harmonic mirror B10 and the laser input mirror 3, so that the mode matching of the pump light and the oscillation light is realized, and the light beam quality of output 1710nm and 2300nm laser is improved.
Example 5
An optical parametric oscillator for transparent or white plastic welding is provided according to embodiment 1, with the difference that: the optical superlattice crystal is periodically polarized homogeneous lithium tantalate crystal (PPCLT).

Claims (12)

1. An optical parametric oscillator for welding transparent or white plastics is characterized by comprising a semiconductor laser A, a collimation focusing system A, a resonant cavity and a filter plate which are sequentially arranged along a light path; the resonant cavity comprises a laser input mirror, a nonlinear optical crystal and a laser output mirror;
the nonlinear optical crystal is a periodically polarized optical superlattice crystal, the period of the optical superlattice crystal is 20-30 mu m, and the temperature of the optical superlattice crystal is controlled at 50-200 ℃; the working wavelength of the semiconductor laser A is 800-1000 nm;
after the pump light output by the semiconductor laser A is collimated by the collimating and focusing system A, the pump light is incident into the resonant cavity, the pump light is incident onto the nonlinear optical crystal after passing through the laser input mirror, the nonlinear optical crystal is pumped, optical oscillation is formed in the resonant cavity, signal light and idle frequency light are generated, and the signal light and the idle frequency light are coupled and output by the laser output mirror; the filter filters laser with other wavelengths and outputs laser with 1710nm and 2300nm wavelengths.
2. An optical parametric oscillator for transparent or white plastic welding according to claim 1, wherein the period of the optical superlattice crystal is 29 μm, the temperature of the optical crystal is controlled at 134 ℃, and the operating wavelength of the semiconductor laser A is 808nm or 980 nm.
3. An optical parametric oscillator for transparent or white plastic welding according to claim 1, characterized in that the optical superlattice crystal is any one of periodically polarized lithium niobate crystal, periodically polarized potassium titanium oxide phosphate crystal, periodically polarized lithium tantalate crystal, periodically polarized congruent lithium niobate crystal and periodically polarized congruent lithium tantalate crystal.
4. An optical parametric oscillator for transparent or white plastic welding according to claim 1, wherein the optical parametric oscillator further comprises a semiconductor laser B and a collimating and focusing system B, the resonant cavity further comprises a 45 ° harmonic mirror a; the laser device comprises a semiconductor laser device B, a collimation focusing system B, a 45-degree harmonic mirror A and a nonlinear optical crystal, wherein the semiconductor laser device B, the collimation focusing system B, the 45-degree harmonic mirror A and the nonlinear optical crystal are sequentially arranged along a light path, the 45-degree harmonic mirror A and the light path form a 45-degree included angle, a laser output mirror is arranged on one side of the 45-degree harmonic mirror A and is perpendicular to the light path, and the working wavelength of the semiconductor laser device B is 800-1000 nm.
5. The optical parametric oscillator for welding of transparent or white plastics according to claim 4, wherein the resonant cavity further comprises a 45 ° harmonic mirror B, the 45 ° harmonic mirror B is disposed between the collimating and focusing system A and the nonlinear optical crystal, and the 45 ° harmonic mirror B forms an included angle of 45 ° with the optical path; the laser input mirror is arranged on one side of the 45-degree harmonic mirror B and is perpendicular to the light path.
6. An optical parametric oscillator for welding of transparent or white plastics according to claim 1, wherein the material of the laser input mirror and the laser output mirror is calcium fluoride crystal, mid-infrared quartz or ZnSe crystal.
7. An optical parametric oscillator for welding of transparent or white plastic according to claim 1, wherein the angle a between the filter and the optical path satisfies: a is more than 10 degrees and less than 45 degrees.
8. An optical parametric oscillator for welding transparent or white plastics according to any one of claims 1 to 7, wherein the laser input mirror and the laser output mirror are coated with a dielectric film, the laser input mirror is coated with a pump light antireflection film, a high reflection film with a wavelength of 1710nm and 2300nm, and the laser output mirror is coated with a partially transmissive film with a wavelength of 1710nm and 2300 nm.
9. An optical parametric oscillator for welding of transparent or white plastics according to claim 5, wherein the output modes of the semiconductor laser A and the semiconductor laser B are one of free space direct output, optical fiber coupling output, stacked array output and linear array output.
10. An optical parametric oscillator for welding of transparent or white plastic according to any one of claims 4, 5 and 9, wherein the collimating and focusing system a and the collimating and focusing system B each comprise two lenses and a waveguide element, the two lenses being arranged in parallel with each other, and the waveguide element being arranged between the two lenses.
11. An optical parametric oscillator for transparent or white plastic soldering according to claim 2, wherein the operating wavelength of the semiconductor laser a is 980 nm.
12. An optical parametric oscillator for transparent or white plastic welding according to claim 4, wherein the semiconductor laser B has an operating wavelength of 808nm or 980 nm.
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