CN112186478A - Laser with adjustable power proportion and pulse interval and method - Google Patents

Laser with adjustable power proportion and pulse interval and method Download PDF

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Publication number
CN112186478A
CN112186478A CN202010955650.7A CN202010955650A CN112186478A CN 112186478 A CN112186478 A CN 112186478A CN 202010955650 A CN202010955650 A CN 202010955650A CN 112186478 A CN112186478 A CN 112186478A
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laser
raman
wavelength
light
dual
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钟凯
盛泉
刘阳
乔鸿展
丁欣
徐德刚
姚建铨
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Tianjin University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/0619—Coatings, e.g. AR, HR, passivation layer
    • H01S3/0621—Coatings on the end-faces, e.g. input/output surfaces of the laser light
    • H01S3/0623—Antireflective [AR]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08086—Multiple-wavelength emission
    • H01S3/0809—Two-wavelenghth emission
    • 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
    • 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
    • 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
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1123—Q-switching
    • H01S3/115—Q-switching using intracavity electro-optic devices
    • 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
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1123—Q-switching
    • H01S3/117—Q-switching using intracavity acousto-optic devices
    • 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
    • H01S3/30—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects

Abstract

The invention discloses a laser with adjustable power proportion and pulse interval and a method thereof, which are used for realizing 1150-1200 nm waveband dual-wavelength near-infrared laser and 575-600 nm dual-wavelength yellow light. The dual-wavelength Raman laser adopts a coaxial pumping structure, utilizes two laser gain media and one Raman crystal, and realizes dual-wavelength Raman light operation by taking dual-wavelength fundamental frequency light generated by the two laser gain media as an excitation source of the Raman laser, thereby realizing dual-wavelength yellow light output by carrying out frequency doubling on the dual-wavelength Raman laser in a cascade quasi-phase matching frequency doubling crystal on the basis. The power proportion and the pulse time interval of the dual-wavelength fundamental frequency light can be flexibly adjusted by changing the position of a pump light focusing point in the laser gain medium or changing the wavelength of the pump light, and meanwhile, the power proportion and the pulse time interval of the dual-wavelength Raman laser can be adjusted by exciting the Raman laser in the cavity, so that the dual-wavelength frequency-doubled yellow light output with adjustable power proportion and pulse interval is realized by frequency doubling outside the cavity.

Description

Laser with adjustable power proportion and pulse interval and method
Technical Field
The invention relates to the field of all-solid-state lasers and nonlinear optical frequency conversion, in particular to a dual-wavelength intracavity Raman laser with adjustable power proportion and pulse interval and a frequency doubling dual-wavelength yellow laser.
Background
The dual-wavelength laser has great scientific research value and wide application prospect in the application and research fields of precision measurement, spectral analysis, remote sensing, nonlinear frequency conversion and the like, particularly the tunable dual-wavelength laser with similar wavelength can be used for a coherent radiation source for generating terahertz wave band by difference frequency, and is an important research direction in the field of optoelectronics at present.
The current methods for generating dual wavelength laser output are mainly:
1. two independent lasers are utilized to be combined into dual-wavelength laser, but the method has high implementation cost and large volume and weight, and the combination is difficult if the two wavelengths are close and the polarization directions are the same. In addition, for the pulsed laser, a complex pulse synchronization system needs to be added to realize pulse synchronization or time interval adjustment of the dual-wavelength laser, and the overall structure is very complex (j.opt.soc.am.b., 2007,24(9): 2509) -.
2. Two nonlinear crystals of different types, different cutting angles or different quasi-phase matching periods are excited by single-wavelength laser, and dual-wavelength laser output is realized in an optical parametric oscillator through the second-order nonlinear effect of the crystals, and the mode has simple structure and lower cost, but cannot tune the power proportion and pulse interval of the dual-wavelength laser (appl.Phys.Lett.,2016,108(1): 011104).
3. A dual-resonance optical parametric oscillator formed by pumping a crystal by using single-wavelength laser enables signal light and idle frequency light of the optical parametric oscillator to start and output simultaneously, but the mode can only work near a degeneracy point of a phase matching curve generally, and tuning of dual-wavelength laser power ratio and pulse interval cannot be realized (Opt.express,2016,24(20): 23368-.
4. The composite energy level structure of a single laser gain medium is utilized to simultaneously output dual-wavelength fundamental frequency light as a dual-wavelength excitation source in the optical parametric oscillator, and dual-wavelength signal light output of the optical parametric oscillator is realized in a nonlinear crystal. In the method, due to gain competition between two fundamental frequency light wavelengths, the light stability of a dual-wavelength signal output by the excitation light parametric oscillator is poor, and tuning of dual-wavelength power ratio and pulse interval cannot be realized (J.Phys.D: appl.Phys.,2015,49(6): 065101).
5. The two laser crystals are coaxially pumped by the same pump source to realize dual-wavelength laser with adjustable power proportion and pulse interval, and the frequency can be expanded by combining an optical parametric oscillator excited by an inner cavity to realize dual-signal optical output with adjustable power proportion and pulse interval (Opt.express,2018,26(16):20768 and 20716). The method utilizes the second-order nonlinear effect of the crystal, is limited by the second-order nonlinear gain although the scheme is flexible, and is difficult to realize dual-wavelength signal light close to the fundamental frequency light.
Overall, the disadvantages and shortcomings of the existing dual wavelength laser technology are: the realization schemes of most dual-wavelength lasers have the problems of complex structure, high cost, poor stability and the like, and the power proportion and the pulse interval of dual-wavelength signal light can not be adjusted generally. Although the coaxial pumping dual-wavelength laser realizes the tuning of power proportion and pulse interval and realizes the expansion of laser frequency by combining the optical parametric oscillator, the expansion mode is only limited to the optical parametric oscillation technology based on the second-order nonlinear effect. The wavelengths generated by the optical parametric oscillator under the excitation of Nd-YAG laser are mostly located in wave bands of 1.5-1.6 μm, 2 μm, 3-5 μm and the like. YAG laser outputs a wave band (such as 1.1-1.2 μm) with a wavelength close to 1.06 μm, which is limited by second-order nonlinear gain, and is difficult to realize by an optical parametric oscillation technology, so that the laser frequency of the wave band (1.1-1.2 μm) can not be doubled to generate double-wavelength frequency-doubled yellow light with adjustable power ratio and pulse interval.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a dual-wavelength intracavity Raman laser with adjustable power proportion and pulse interval, a frequency-doubled dual-wavelength yellow light laser and a method. The power proportion and the pulse time interval of the dual-wavelength fundamental frequency light can be flexibly adjusted by changing the position of a pump light focusing point in the laser gain medium or changing the wavelength of the pump light, and meanwhile, the power proportion and the pulse time interval of the dual-wavelength Raman laser can be adjusted by exciting the Raman laser in the cavity, so that the dual-wavelength frequency-doubled yellow light output with adjustable power proportion and pulse interval is realized by frequency doubling outside the cavity. The invention has simple and compact structure, convenient tuning of the power proportion and pulse interval of the dual-wavelength Raman laser and the frequency-doubled yellow light, and important application prospect in the fields of precision measurement, spectral analysis, laser medical treatment, nonlinear optical frequency conversion and the like.
The purpose of the invention is realized by the following technical scheme:
a laser with adjustable power proportion and pulse interval comprises a pumping source, a pumping coupling system, a fundamental frequency light total reflection mirror, a first laser gain medium, a second laser gain medium, a Q-switching device, a Raman laser total reflection mirror, a Raman crystal, a Raman laser output mirror, a Raman laser focusing mirror, a frequency doubling crystal and a low-pass filter which are arranged in sequence;
the Raman laser output mirror is simultaneously and totally reflecting the fundamental frequency light, wherein the wavelength of the fundamental frequency light is in the range of 1040-1080 nm; under the feedback action of a fundamental frequency light resonant cavity formed by the fundamental frequency light total reflection mirror and the Raman laser output mirror, two coaxial first laser gain media and second laser gain media generate dual-wavelength fundamental frequency light; generating a third-order nonlinear effect, namely stimulated Raman scattering, under the action of a Raman laser resonant cavity formed by a Raman laser total reflection mirror and a Raman laser output mirror, converting dual-wavelength fundamental frequency light into dual-wavelength Raman laser in a Raman crystal, wherein the wavelength of the Raman laser is located in a 1150-1200 nm wave band and is output through the Raman laser output mirror; the dual-wavelength Raman laser is focused in the frequency doubling crystal through the Raman laser focusing mirror and converted into dual-wavelength yellow light, the yellow light wavelength is located in a 575-600 nm wave band, and the dual-wavelength Raman laser is filtered through the low-pass filter and then output.
Furthermore, the first laser gain medium and the second laser gain medium are composed of two different kinds of laser crystals or two same kinds of laser crystals with different cutting directions, and active ions of the laser crystals are trivalent neodymium ions (Nd)3+) And two end faces of the laser crystal are plated with a pumping light antireflection film and a fundamental frequency light antireflection film.
Furthermore, the Q-switching device is an acousto-optic Q-switching device or an electro-optic Q-switching device, and two ends of the Q-switching device are plated with fundamental frequency light antireflection films for realizing the pulse operation of fundamental frequency light and improving the conversion efficiency of the stimulated Raman scattering process by improving the peak power.
Furthermore, the lens of the fundamental frequency light total reflection mirror is a plane mirror or a plano-concave mirror, and is plated with a fundamental frequency light total reflection film and a pumping light antireflection film; the Raman laser total reflection mirror is a concave mirror or a flat mirror and is plated with a fundamental frequency light antireflection film and a Raman laser high reflection film; two end faces of the Raman crystal are plated with a fundamental frequency light antireflection film and a Raman laser antireflection film; the Raman laser output mirror is a concave mirror or a flat mirror and is plated with a Raman laser part transmission film; the Raman laser focusing lens is a convex lens and is plated with a Raman laser antireflection film; the frequency doubling crystal is plated with an antireflection film of Raman laser and frequency doubling yellow light; the low-pass filter mirror is plated with a Raman laser high-reflection film and a frequency-doubling yellow light antireflection film.
The invention also provides another technical scheme: a method for adjusting a laser with adjustable power ratio and pulse interval comprises the following steps:
pumping the first laser gain medium and the second laser gain medium by pump light emitted by a pump source through a pump coupling system, absorbing the pump light by activated particles in the first laser gain medium and the second laser gain medium to generate population inversion, and generating dual-wavelength fundamental frequency light pulse oscillation through the feedback of a fundamental frequency light resonant cavity after a Q-switching device is opened;
the positions of pump light focus points in the first laser gain medium and the second laser gain medium are adjusted by changing the front and back positions of the pump coupling system, so that the volumes of pump light in the first laser gain medium and the second laser gain medium are changed, and the population density of reversed particles in the first laser gain medium and the second laser gain medium is changed; or the wavelength of the pump light is changed by adjusting the temperature of the pump source, so that the power of the pump light absorbed by the first laser gain medium and the second laser gain medium is changed, and the population density of the reversed particles in the first laser gain medium and the second laser gain medium is changed;
the photon number density and pulse establishing time of the dual-wavelength fundamental frequency light in the fundamental frequency light resonant cavity are influenced by the change of the reversed population number density in the first laser gain medium and the second laser gain medium, so that the dual-wavelength fundamental frequency light pulse with adjustable power proportion and pulse interval is realized in the fundamental frequency light resonant cavity; the Raman crystal and the Raman laser resonant cavity are positioned in the fundamental frequency light resonant cavity, the stimulated Raman scattering effect is respectively excited in the Raman crystal while the dual-wavelength fundamental frequency light oscillates to generate Raman light and Stokes light with two wavelengths, the Raman light and the Stokes light are continuously transmitted back and forth through the feedback effect of the Raman laser resonant cavity to realize amplification, and finally the Raman light and the Stokes light exceed the threshold value of the Raman laser and are output through the Raman laser output mirror;
because the photon number density and the pulse establishment time of each Raman laser wavelength are related to the photon number density and the pulse establishment time of corresponding fundamental frequency light in the cavity, the power ratio and the pulse interval of two wavelengths in the dual-wavelength Raman laser can be adjusted by adjusting the front and back positions of the pump coupling system or changing the temperature of the pump source; the output dual-wavelength Raman laser is focused by a Raman laser focusing lens and then enters a frequency doubling crystal, the frequency doubling crystal is a cascaded Periodically Poled Lithium Niobate (PPLN) crystal and is divided into two sections which are respectively poled into reversal domains with different periods, quasi-phase matching frequency doubling can be respectively realized on the Raman laser with two wavelengths, and the generated dual-wavelength yellow light is output after the residual Raman laser is filtered out by a low-pass filter; because the power ratio and the pulse interval of the two wavelengths of the dual-wavelength Raman laser are adjustable, the power ratio and the pulse interval of the two wavelengths of the double-wavelength yellow light after frequency multiplication are also adjustable, and the realization way is to adjust the front and back positions of the pumping coupling system or change the temperature of the pumping source.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1. the invention realizes a power proportion and pulse interval adjustable dual-wavelength intracavity Raman laser and frequency doubling dual-wavelength yellow light laser, only needs a pumping source, two laser gain media, a Raman crystal and a frequency doubling crystal, two laser gain media which are coaxially arranged can generate dual-wavelength fundamental frequency light under the end pumping of the same pumping source, the wavelength of the fundamental frequency light is in the range of 1040-1080 nm, and the power proportion and the pulse interval of the dual-wavelength fundamental frequency light oscillating in the cavity can be flexibly controlled by adjusting the position of a pumping light focus point in the laser gain media or the wavelength of the pumping light;
2. the Raman laser resonant cavity is arranged in the fundamental frequency light resonant cavity, the high power density in the fundamental frequency light resonant cavity can be fully utilized, the high-efficiency frequency conversion is realized based on the third-order nonlinear effect of the Raman crystal, and the dual-wavelength Raman laser with the wave band of 1150-1200 nm is generated and output; the dual-wavelength Raman laser is focused and then enters a frequency doubling crystal, and frequency doubling is carried out under the phase matching condition to convert the dual-wavelength Raman laser into dual-wavelength yellow light with a wave band of 575-600 nm. Because the power proportion and the pulse interval of the double-wavelength fundamental frequency light for exciting the double-wavelength Raman laser are adjustable, the power proportion and the pulse interval of the generated double-wavelength Raman laser and the double-wavelength yellow light generated after frequency doubling are adjustable.
3. The invention utilizes the coaxial pumping structure to combine the frequency conversion based on the third-order nonlinear effect stimulated Raman scattering, can realize the dual-wavelength Raman laser with compact structure and stable output, overcomes the defect that the optical parametric oscillation technology based on the second-order nonlinear effect is difficult to directly convert the base frequency light in the range of 1040-1080 nm into the 1150-1200 nm band, has flexible and adjustable power proportion and pulse interval of the dual-wavelength Raman laser, generates dual-wavelength yellow light after the Raman laser frequency doubling, can cover the Na yellow light band, and has important value in the applications of precision measurement, spectral analysis, nonlinear frequency conversion, Na guide star and the like.
Drawings
Fig. 1 is a schematic structural diagram of a laser according to the present invention.
Reference numerals: the device comprises a 1-pumping source, a 2-pumping coupling system, a 3-fundamental frequency light total reflection mirror, a 4-first laser gain medium, a 5-second laser gain medium, a 6-Q-switching device, a 7-Raman laser total reflection mirror, an 8-Raman crystal, a 9-Raman laser output mirror, a 10-Raman laser focusing mirror, an 11-frequency doubling crystal and a 12-low-pass filter.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, the dual-wavelength intracavity raman laser and the frequency-doubled dual-wavelength yellow laser include a pumping source 1, a pumping coupling system 2, a fundamental-frequency light total reflection mirror 3, a first laser gain medium 4, a second laser gain medium 5, a Q-tuning device 6, a raman laser total reflection mirror 7, a raman crystal 8, a raman laser output mirror 9, a raman laser focusing mirror 10, a frequency-doubled crystal 11, and a low-pass filter 12, which are sequentially arranged. The pump source 1 is a semiconductor laser coupled and output by an optical fiber, the central wavelength of output laser is 808nm, the core diameter of the optical fiber is 400 microns, the numerical aperture is 0.22, and the laser output by the pump source 1 is guided into the pump coupling system 2 through the energy transmission optical fiber. The pump coupling system 2 is a 1:2 coupling lens group, and can focus pump light to be incident into the first laser gain medium 4 and the second laser gain medium 5. First laser beamThe beneficial medium 4 is Nd, YAG crystal, Nd3+A doping concentration of 0.6%, a crystal size of 4mm × 4mm × 7mm, and a second laser gain medium 5 of Nd: YAP crystal, Nd cut along the b-axis3+The doping concentration is 1%, the crystal size is 3mm multiplied by 10mm, and two end faces of the two laser gain media are respectively plated with antireflection films with the thickness of about 800nm and about 1050 nm. The fundamental frequency light resonant cavity is composed of a fundamental frequency light total reflection mirror 3 and a Raman laser output mirror 9, the fundamental frequency light total reflection mirror 3 is a plano-concave mirror, the curvature radius of a concave surface is 500mm, a high reflection film near 1050nm is plated on the concave surface of the mirror, and an antireflection film near 800nm is plated on a plane on one side of the pumping source 1. The acousto-optic medium of the Q-switching device 6 is fused quartz, the length of the medium is 35mm, the ultrasonic working frequency is 41MHz, the driving power is 20W, and the Q-switching frequency is 10 kHz. The Raman laser resonant cavity consists of a Raman laser total reflection mirror 7 and a Raman laser output mirror 9, wherein the Raman laser total reflection mirror 7 is a flat mirror and is plated with a 1040-1080 nm waveband antireflection film and a 1150-1200 nm waveband high reflection film. The Raman laser output mirror 9 is a flat mirror, a 1040-1080 nm waveband high-reflection film and 1150-1200 nm partial transmission films are plated, the 1150-1200 nm Raman light transmittance is about 10%, and the substrate of the cavity mirror lens is made of K9 glass. The Raman crystal 8 is YVO cut along the a axis4The crystal has the size of 3mm multiplied by 30mm, and both end faces are plated with 1040-1080 nm wave band high-reflection films and 1150-1200 nm wave band antireflection films. The Raman laser focusing lens 10 is a biconvex lens, the focal length is 200mm, and two surfaces of the Raman laser focusing lens are plated with anti-reflection films with wave bands of 1150-1200 nm. The frequency doubling crystal 11 is a cascade Period Polarization Lithium Niobate (PPLN) crystal, the size of the crystal is 1mm multiplied by 5mm multiplied by 30mm, two polarization periods of 9.6 microns and 9.1 microns are sequentially arranged along the light propagation direction, and anti-reflection films with wave bands of 1150-1200 nm and 575-600 nm are plated on two end faces of the frequency doubling crystal 11. The low-pass filter 12 has high reflection for the wavelength band of 1000-1300 nm and high transmission for the wavelength band of 500-650 nm.
The first laser gain medium 4Nd: YAG and the second laser gain medium 5Nd: YAP absorb pump light, the energy state of the activated particles is transited from the ground state to the excited state, so that the energy of the pump light is stored in the upper energy level of the laser, when the Q-switched device 6 is in the closed state, the number of particles in the upper energy level is continuously accumulated and generates a large number of reversed numbers of particles, when the Q-switched device 6 is opened, the gain exceeds the loss, the laser oscillation condition is satisfied,the intense stimulated radiation amplification is rapidly realized through the feedback of the fundamental frequency light resonant cavity, giant pulse fundamental frequency light oscillation is established in the resonant cavity, the wavelength of fundamental frequency laser is 1064nm and 1079nm, and the pulse repetition frequency is consistent with the Q-switching frequency and is 10 kHz. Simultaneously, 8YVO is passed through Raman crystal4The third-order nonlinear effect of the Raman laser is that base frequency light of 1064nm and 1079nm generates stimulated Raman scattering under the action of a Raman laser resonant cavity, frequency shift of the base frequency light of dual-wavelength is converted to 1176nm and 1196nm, and dual-wavelength laser of 1176nm and 1196nm is output through a Raman laser output mirror 9. The dual-wavelength Raman laser passes through a Raman laser focusing mirror 10, is converged into a light spot with the diameter of about 100 mu m and is incident on a frequency doubling crystal 11, dual-wavelength yellow light of 588nm and 598nm is generated through quasi-phase matching frequency doubling, the residual Raman light is filtered through a low-pass filter 12, and the yellow light is output. When the power of the pump light is 16W, and the focal point of the pump light is 3mm away from the left end face in the first gain medium 4, the total power of the output dual-wavelength Raman laser is 1.88W, wherein the power of 1176nm is 1.12W, the power of 1196nm is 0.76W, and the power of 1176nm is earlier than that of 1196nm Raman optical pulse by 5ns, and the Raman optical pulse is generated and output; after frequency multiplication, the 588nm yellow light power is 0.42W, the 598nm yellow light power is 0.25W, wherein 588nm pulses are generated and output 5ns earlier than 598nm pulses.
The method comprises the steps that activated particles in a first laser gain medium 4Nd: YAG and a second laser gain medium 5Nd: YLF absorb pump light to generate population inversion, the positions of a pump light focus point in the first laser gain medium 4 and the second laser gain medium 5 are adjusted by changing the front-back position of a 1:2 coupling lens in a pump coupling system 2, the volumes of the pump light in the first laser gain medium 4 and the second laser gain medium 5 can be changed, the population density of the inversion particles in the first laser gain medium 4 and the second laser gain medium 5 is changed, or the wavelength of the pump light is changed by adjusting the temperature of a pump source 1, the absorption coefficients of the first laser gain medium 4 and the second laser gain medium 5 are changed, the power of the pump light absorbed by the first laser gain medium 4 and the second laser gain medium 5 is changed, and the first laser gain medium 4, the second laser gain medium 5, the pump light power absorbed by the first laser gain medium 4, the second laser gain medium 5, The inversion population density in the second laser gain medium 5 changes. The first laser gain medium 4 and the second laser gain medium 5 have inverted numbers of particlesThe density change affects the photon density and pulse establishing time of the 1064nm and 1079nm double-wavelength fundamental-frequency light in the fundamental-frequency light resonant cavity consisting of the fundamental-frequency light total reflection mirror 3 and the Raman laser output mirror 9. Meanwhile, the Raman crystal 8YVO4The stimulated Raman scattering effect can be generated, the fundamental laser is converted into Raman laser through the Raman scattering effect of the mobile phone under the action of a Raman laser resonant cavity consisting of a Raman laser total reflection mirror 7 and a Raman laser output mirror 9, so that the photon density and the pulse establishing time of 1176nm and 1196nm dual-wavelength Raman laser in the Raman laser resonant cavity are changed, the adjustment of the power proportion and the pulse time interval of the 1176nm and 1196nm dual-wavelength Raman laser output by the Raman laser output mirror 9 is realized, and the power proportion and the pulse time interval of frequency doubling dual-wavelength yellow light generated by a frequency doubling crystal 11 are adjustable. When the power of the pump light is 16W, and the distance between the pump light focal point and the left end surface of the first gain medium 4 is 4mm, the total power of the output dual-wavelength Raman laser is 1.79W, wherein the power of 1176nm is 0.90W, and the power of 1196nm is 0.89W; after frequency multiplication, the power of 588nm yellow light is 0.34W, the power of 598nm yellow light is 0.33W, the power of the dual-wavelength Raman laser and the power of the frequency multiplication yellow light are almost equal, and pulses are almost synchronous on a time domain.
In summary, the dual-wavelength intracavity raman laser and the frequency-doubled dual-wavelength yellow laser provided by the embodiments of the present invention have adjustable power ratios and pulse intervals, and employ a coaxial pumping structure, which utilizes two laser gain media, a raman crystal and a frequency-doubled crystal, and uses dual-wavelength fundamental light generated by the two laser gain media as a dual excitation source of the raman crystal to excite the third-order nonlinear effect of the raman crystal in the fundamental-frequency light cavity, thereby realizing efficient generation of the dual-wavelength raman laser through stimulated raman scattering. The power proportion and the pulse interval of the dual-wavelength Raman laser can be flexibly controlled by adjusting the position of a pump light focusing point in the laser gain medium or the wavelength of the pump light, and then the dual-wavelength yellow laser with adjustable power proportion and pulse interval is realized by frequency doubling. The invention solves the problems of untuneable power ratio and pulse interval, complex structure and poor system stability of the dual-wavelength laser in the prior art, and realizes the dual-wavelength Raman laser output based on the third-order nonlinear effect, namely stimulated Raman scattering, and the high-efficiency dual-wavelength frequency-doubled yellow light output based on the cascaded PPLN crystal.
In the embodiment of the invention, the types, doping concentrations or sizes of the laser gain medium, the Raman crystal and the frequency doubling crystal, and the specification sizes, curvature radii, coating indexes and other parameters of the fundamental frequency light total reflection mirror, the Raman laser output mirror and the Raman laser focusing mirror can be selected according to actual needs.
In the embodiment of the present invention, except for the specific description of the model of each device, the model of other devices is not limited, as long as the device can perform the above functions.
The present invention is not limited to the above-described embodiments. The foregoing description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention, and the above specific embodiments are merely illustrative and not restrictive. Those skilled in the art can make many changes and modifications to the invention without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (5)

1. A laser with adjustable power proportion and pulse interval is characterized by comprising a pumping source (1), a pumping coupling system (2), a fundamental frequency light total reflection mirror (3), a first laser gain medium (4), a second laser gain medium (5), a Q-switching device (6), a Raman laser total reflection mirror (7), a Raman crystal (8), a Raman laser output mirror (9), a Raman laser focusing mirror (10), a frequency doubling crystal (11) and a low-pass filter mirror (12) which are sequentially arranged;
the Raman laser output mirror (9) is used for totally reflecting fundamental frequency light at the same time, wherein the wavelength of the fundamental frequency light is in the range of 1040-1080 nm; under the feedback action of a fundamental frequency light resonant cavity formed by the fundamental frequency light total reflection mirror (3) and the Raman laser output mirror (9), two coaxial first laser gain media (4) and second laser gain media (5) generate dual-wavelength fundamental frequency light; generating a third-order nonlinear effect, namely stimulated Raman scattering, under the action of a Raman laser resonant cavity formed by a Raman laser total reflection mirror (7) and a Raman laser output mirror (9), converting dual-wavelength fundamental frequency light into dual-wavelength Raman laser in a Raman crystal (8), wherein the wavelength of the Raman laser is located in a 1150-1200 nm wave band and is output through the Raman laser output mirror (9); the dual-wavelength Raman laser is focused in a frequency doubling crystal (11) through a Raman laser focusing mirror (10) and converted into dual-wavelength yellow light, the yellow light wavelength is located in a 575-600 nm wave band, and the dual-wavelength Raman laser is filtered through a low-pass filter mirror (12) and then is output.
2. The laser with adjustable power ratio and pulse interval as claimed in claim 1, wherein the first laser gain medium (4) and the second laser gain medium (5) are composed of two different kinds of laser crystals or two same kinds of laser crystals with different cutting directions, and the active ions of the laser crystals are trivalent neodymium ions (Nd)3+) And two end faces of the laser crystal are plated with a pumping light antireflection film and a fundamental frequency light antireflection film.
3. The laser with adjustable power ratio and pulse interval as claimed in claim 1, wherein the Q-switching device (6) is an acousto-optic Q-switching device or an electro-optic Q-switching device, and both ends of the Q-switching device (6) are coated with anti-reflection films for fundamental frequency light, so as to implement pulsed operation of the fundamental frequency light, and improve the conversion efficiency of the stimulated raman scattering process by improving the peak power.
4. The laser with adjustable power ratio and pulse interval as claimed in claim 1, wherein the mirror of the fundamental frequency total reflection mirror (3) is a flat mirror or a flat concave mirror, and is coated with a fundamental frequency total reflection film and a pumping light reflection reducing film; the Raman laser total reflection mirror (7) is a concave mirror or a flat mirror and is plated with a fundamental frequency light antireflection film and a Raman laser high reflection film; two end faces of the Raman crystal (8) are plated with a fundamental frequency light antireflection film and a Raman laser antireflection film; the Raman laser output mirror (9) is a concave mirror or a flat mirror and is plated with a Raman laser part transmission film; the Raman laser focusing lens (10) is a convex lens and is plated with a Raman laser antireflection film; the frequency doubling crystal (11) is plated with an antireflection film for Raman laser and frequency doubling yellow light; the low-pass filter (12) is plated with a Raman laser high-reflection film and a frequency-doubling yellow light reflection reducing film.
5. A method for adjusting a laser with adjustable power ratio and pulse interval is characterized by comprising the following steps:
pumping light emitted by a pumping source (1) pumps a first laser gain medium (4) and a second laser gain medium (5) through a pumping coupling system (2), activated particles in the first laser gain medium (4) and the second laser gain medium (5) absorb the pumping light to generate population inversion, and after a Q-switching device (6) is opened, dual-wavelength fundamental frequency light pulse oscillation is generated through feedback of a fundamental frequency light resonant cavity;
the positions of pump light focus points in the first laser gain medium (4) and the second laser gain medium (5) are adjusted by changing the front and back positions of the pump coupling system (2), so that the volumes of pump light in the first laser gain medium (4) and the second laser gain medium (5) are changed, and the number density of reversed particles in the first laser gain medium (4) and the second laser gain medium (5) is changed; or the wavelength of the pump light is changed by adjusting the temperature of the pump source (1), so that the power of the pump light absorbed by the first laser gain medium (4) and the second laser gain medium (5) is changed, and the population density of the inversion particles in the first laser gain medium (4) and the second laser gain medium (5) is changed;
the photon number density and the pulse establishing time of the dual-wavelength fundamental frequency light in the fundamental frequency light resonant cavity are influenced by the change of the reversed population number density in the first laser gain medium (4) and the second laser gain medium (5), so that the dual-wavelength fundamental frequency light pulse with adjustable power proportion and pulse interval is realized in the fundamental frequency light resonant cavity; the Raman crystal (8) and the Raman laser resonant cavity are positioned in the fundamental frequency light resonant cavity, the stimulated Raman scattering effect is respectively excited in the Raman crystal (8) while the dual-wavelength fundamental frequency light oscillates, Raman light and Stokes light with two wavelengths are generated, the Raman light and the Stokes light are continuously transmitted back and forth under the feedback action of the Raman laser resonant cavity to realize amplification, and finally the Raman light and the Stokes light exceed the threshold value of the Raman laser and are output through a Raman laser output mirror (9);
because the photon number density and the pulse establishment time of each Raman laser wavelength are related to the photon number density and the pulse establishment time of corresponding fundamental frequency light in the cavity, the power ratio and the pulse interval of two wavelengths in the dual-wavelength Raman laser can be adjusted by adjusting the front and back positions of the pump coupling system (2) or changing the temperature of the pump source (1); the output dual-wavelength Raman laser is focused by a Raman laser focusing mirror (10) and then enters a frequency doubling crystal (11), the frequency doubling crystal (11) is a cascade Periodically Poled Lithium Niobate (PPLN) crystal and is divided into two sections which are respectively poled into inversion domains with different periods, quasi-phase matching frequency doubling can be respectively realized on the Raman laser with two wavelengths, and the generated dual-wavelength yellow light is output after the residual Raman laser is filtered by a low-pass filter mirror (12); because the power ratio of the two wavelengths and the pulse interval of the dual-wavelength Raman laser are adjustable, the power ratio of the two wavelengths and the pulse interval of the frequency-doubled dual-wavelength yellow light are adjusted by adjusting the front and back positions of the pumping coupling system (2) or changing the temperature of the pumping source (1).
CN202010955650.7A 2020-09-11 2020-09-11 Laser with adjustable power proportion and pulse interval and method Pending CN112186478A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114927932A (en) * 2022-07-21 2022-08-19 山东省科学院激光研究所 Multipurpose 1064nm laser capable of automatically switching working modes
CN115296136A (en) * 2022-07-15 2022-11-04 山西大学 Pulse laser space-time distribution regulation and control laser and method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115296136A (en) * 2022-07-15 2022-11-04 山西大学 Pulse laser space-time distribution regulation and control laser and method
CN114927932A (en) * 2022-07-21 2022-08-19 山东省科学院激光研究所 Multipurpose 1064nm laser capable of automatically switching working modes

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