CN1697270A - Method and device for generating green laser from semiconductor pump in large power - Google Patents

Abstract

The equipment includes following structures: five pieces of semiconductor device is as one group including Nd:YAG laser crystals arranged along circumferential equilateral pentagon; 16 groups of semiconductor pump subassemblies are arranged in long direction with equal distance between each other, and light in 808nm is emitted; through Nd:YAG crystal to remove pumping as well as through optimal resonant cavity in concave - flat cavity structure so as to form light in fundamental frequency; green laser light is generated after modulation by dual acousto-optic Q switch and through frequency doubling by KTP crystal; related water-cooling channel, laser power source and water-cooling thermostat are provided. Power of average output of green light 532nm is reached to 108W. Features are: 1-40KHz adjustable repetition rate, high efficiency, good quality of light beam, and long service life. The invention is applicable to communication, machining and display etc.

Description

High power semi-conductor pumping green laser method for generation and device

Technical field

The present invention relates to a kind of high power semi-conductor pumping green laser method for generation and device, belong to the photoelectron laser technique.

Background technology

The high power semi-conductor pump green light laser is the laser optoelectronic device of a new generation, it is one of developing direction of current photoelectron high-tech product, along with development of semiconductor, the continuous decline of semiconductor laser diode price, the superpower laser of semiconductor diode pump is near the laser of other pump mode, cost descends just exponentially, surpasses the laser of other pump mode the most comprehensively.Adopting Nd:YAG inner cavity frequency-doubling technology is one of important channel of realizing the high power green light light source, this laser adopts flash lamp pumping more at present, single acousto-optic Q modulation is put down-flat resonant cavity technology, because the restriction of factors such as resonant cavity thermal stability and frequency-doubling crystal thermal effect, make green (light) laser running output average power low, and less stable, this has limited its practical application in fields such as optical communication, light manufacturings greatly.

Summary of the invention

The object of the present invention is to provide a kind of high power semi-conductor pumping green laser method for generation and device, this method for generating laser conversion efficiency height, its device output green laser average power can reach hectowatt, stable performance, adjustable repetitive frequency.

The present invention is realized by following technical method and device, it is to send 808nm light by large power semiconductor device, remove pumping Nd:YAG laser crystal, form fundamental frequency light through laserresonator again, modulated by alliteration light Q switching, through ktp crystal frequency multiplication generation green laser, it is mainly by semiconductor laser power supply, laserresonator, compositions such as water-cooled thermostat: it is characterized in that, it is one group by 5 semiconductor device arranging at the circumferential equilateral pentagon of the horizontal section of Nd:YAG laser crystal, it is equal 16 groups of row vertically, form high power semi-conductor pumping assembly, the corresponding configuration water-cooling channel, adopt the resonant cavity of recessed-flat cavity configuration of optimizing, the chamber is long to be 558mm, adopt the KTP frequency-doubling crystal of II class phase matched, the coupling angle is φ=23.6 °: θ=90 °, it is of a size of 7 * 7 * 8mm, the anti-reflection film of both ends of the surface plating 1064nm and 532nm, laser crystal adopts the Nd:YAG crystal bar of φ 6.4 * 150mm, its side hacking, the plane is worn at two ends, the anti-reflection film of plating 1064nm, between Nd:YAG crystal ktp crystal, harmonic reflection mirror is set, at the crystal bar skin water-cooled circular passage is set, the position of and axis vertical at vertical two ends of Nd:YAG crystal, two acoustooptic Q-switchings are set respectively, dispose water-cooling channel simultaneously, the spill completely reflecting mirror that resonant cavity one end is optimized, its radius of curvature is 2m, the other end is provided with the 532nm outgoing mirror, ktp crystal all adopts radially with whole eyeglasses, and the adjustment type frame supports, all the supporting construction bottom is installed on the duralumin, hard alumin ium alloy track of thermal deformation resistant, be positioned in the cabinet again, promptly constituted high power semi-conductor pumping green laser generating means, dispose Laser Power Devices and water-cooled thermostat again, promptly formed the laser generator prototype devices, the green glow average output power of 532nm reaches 108W, unsteadiness is less than 1.03%, repetition rate 1～40KHz is adjustable, has efficient height (overall electrical efficiency can reach 10%), good beam quality, volume is little, characteristics such as long and operating cost of life-span is low can be widely used in laser pumping source in the optical-fibre communications, the industrial lasers Carving Machining, laser display, field such as habitata and military electrooptical countermeasures.

Description of drawings:

Accompanying drawing 1 is a pentagon semiconductor array pumping configuration schematic diagram of the present invention, and wherein, 1 is cooler, and 2 is the Nd:YAG laser crystal, and 3 is semiconductor pumped device, and 4 is quartz glass tube, and 5 is recirculated cooling water.

Accompanying drawing 2 is the structural representation of generating device of laser of the present invention, wherein, 1 is that acoustooptic Q-switching 1,2 is a high-power semiconductor laser pumping assembly, and 3 for being harmonic reflection mirror, 4 is concave mirror, 5 is the Nd:YAG crystal bar, and 6 is acoustooptic Q-switching II, and 7 is the KTP frequency-doubling crystal, 8 is outgoing mirror, and 9 are the output green laser.

Accompanying drawing 3 is a water-cooled thermostat system schematic diagram of the present invention, and wherein, 1 is the split refrigeration machine, and 2 is pressure water tank, and 3 is heating tube, and 4 is filter, and 5 is by-pass valve, and 6 is high-pressure hydraulic pump, and 7 to the laser cold water outlet, and 8 is from the laser heat water return outlet.

Embodiment:

Below in conjunction with accompanying drawing the present invention is illustrated.

As shown in Figure 1, it drives high power semi-conductor pumping assembly by semiconductor laser power supply and sends 808nm light, thisly make around equidistant pump mode that the gain profiles characteristic improves in the operation material, remove pumping Nd:YAG laser crystal with 808nm light, carry out the water-cooled thermostatic control simultaneously, the Nd:YAG laser crystal is with radiation 1064nm photon, resonant cavity through recessed-Ping cavity configuration forms basic frequency laser, basic frequency laser realizes that by ktp crystal II class phase matched frequency multiplication produces the 532nm green laser, make their synchronous working by DG535 signal generator two control cover acousto-optic systems, make acousto-optic reach best off state, two acoustooptic Q-switchings dispose water-cooling channel simultaneously, the spill completely reflecting mirror that resonant cavity one end is optimized, the other end is provided with the 532nm outgoing mirror, as shown in Figure 2; Ktp crystal all adopts radially with whole eyeglasses, and the adjustment type frame supports, all the supporting construction bottom is installed on the duralumin, hard alumin ium alloy track of thermal deformation resistant, be positioned in the cabinet again, promptly constituted high power semi-conductor pumping green laser generating means, dispose Laser Power Devices and water-cooled thermostat again, promptly formed the laser generator prototype devices, the green glow average output power of 532nm reaches 108W.

In device of the present invention, harmonic reflection mirror adopts the fused silica glass of the high saturating and 532nm high-reflecting film layer of plating 1064nm; Two cover acousto-optical device parameters are: driving power is 100W, and operating frequency is 27MHz, and static transmitance is 98.5% (to 1064nm), and diffraction efficiency is 20.5%, and its modulating frequency is 1～50kHz.The constant temperature that carries out to frequency-doubling crystal cools off, increase the coefficient of heat conduction of its crystal, improve the crystal heat transfer rate, reduce the deposition of crystal absorbed power in inside, realization is to effective correction of phase mismatch, frequency-doubling crystal is cooled to 6.0 ℃, adjust the angle (about 0.7 °) of frequency-doubling crystal in resonant cavity simultaneously, adjust the modulating frequency and the impulsive synchronization time of acousto-optic modulator, the acquisition repetition rate is that 20.3kHz, pulse duration 135ns, average power are high power, high repetition frequency green glow (532nm) output of 108W.

Mobile frequency-doubling crystal is to suitable position, make resonant cavity form stable cavity, by the heat sedimentary facies balance of strong cooling, can effectively reduce the frequency-doubling crystal thermal lensing effect by frequency-doubling crystal, thereby realize the steady running of laser with the residual heat absorbed power of crystals.

The present invention has adopted the following theoretical method.

At first adopt the two Q of accent synchronisation measures, increased the peak power of first-harmonic, improved shg efficiency.In order to obtain the output of high power frequency doubled light, design two chambeies all in the optimal parameter running, the total losses that can obtain two chambeies are identical, have

$a_{\mathrm{\ζ}\stackrel{\‾}{\mathrm{\φ}}}=\mathrm{\ζ}\stackrel{\‾}{\mathrm{\φ}}=a_T-\mathrm{\γ}$

From then on draw, the key that obtains the inner cavity frequency-doubling acousto-optic Q modulation laser of high conversion efficiency is to design the high efficiency fundamental frequency best output laser that turns round, and obtains best output coupling a _T, measure average photon density φ in the chamber simultaneously; Utilize this two data design frequency doubling devices, consider device insertion and outgoing mirror transmission loss γ again, make it and the average output of frequency multiplication equivalence transmitance a fundamental wave _{ζ φ}Sum equals best output coupling, thereby obtains best frequency multiplication design.Here n _1e, n _2e, can be by threshold inversion population n _1th, n _2thObtain,

$\frac{n_e}{n_0}=\exp [1-\frac{n_0}{n_{\mathrm{th}}}]$

$n_{1\mathrm{th}}=\frac{a_0+\mathrm{\β}+a_T}{{\mathrm{Bl}}_{\mathrm{YAG}}}$

$n_{1\mathrm{th}}=\frac{a_0+\mathrm{\β}+a_T}{{\mathrm{Bl}}_{\mathrm{YAG}}}$

Utilize the approximate ζ of small-signal can be written as

$\mathrm{\ζ}=2\left(\frac{{5.46d}_{\mathrm{eff}}}{{\mathrm{\λn}}^{3/2}}\right)\left(\frac{{10}^{-9}{l^2}_{\mathrm{NL}}{\mathrm{hvc}}^2}{{4l}_{\mathrm{cav}}}\right){\left(\frac{{\mathrm{\ω}}_{\mathrm{rod}}}{{\mathrm{\ω}}_{\mathrm{NL}}}\right)}^4{\mathrm{\ρ}}^{\left(2\right)}$

Can draw and reduce that to insert loss in the chamber be the key that obtains the high efficiency inner cavity frequency-doubling, establish if the insertion loss of frequency-doubling crystal is 0, then best frequency multiplication ripple output will be exported greater than best fundamental wave running, and greatly reduce threshold value.Simultaneously in the chamber photon density high the time guaranteed high efficiency output.In the present invention's practice,, realize the high efficiency frequency-doubled conversion according to the analysis integrated parameter of adjusting system of above-mentioned theory.

Secondly, apparatus of the present invention adopt flat-matrix resonant cavity of optimizing, have not only increased mode volume but also reduced partial power's density.The advantage that we absorb Z die cavity and straight chamber has been improved the design of resonant cavity, overcome difficult points such as being difficult for adjustment in the measure that reduces optical power density in the resonant cavity, flat-recessed resonant cavity by optimal design, oscillation light beam diameter in the conversion chamber, both increased mode volume, reduced partial power's density again, as accompanying drawing 2.

Once more, apparatus of the present invention adopt the technical measures of frequency-doubling crystal being carried out highly effective refrigeration and adjustment crystal angle compensation matching angle.Highly effective refrigeration significantly reduces the conductive coefficient that crystal temperature effect can improve crystal, the transmission speed of the heat of crystals increases, thereby plane of crystal and temperature inside difference reduce, the phase mismatch of crystal also drops to minimum, we are again according to the temperature variant rule of crystal refractive index, calculate the amount of mismatch of crystalline phase matching angle, compensate amount of mismatch by the angle of adjusting crystal, reduce the phase mismatch of crystal effectively, compensated the thermal effect problem of crystal preferably, improve the shg efficiency of crystal, increase the output of frequency doubled light.Frequency-doubling crystal in inner cavity frequency-doubling Nd:YAG laser is long vertically, the temperature axis that therefore can ignore crystals to variations in temperature, the Q that comprehensively derives in the heat conduction equation based on the heat conduction equation of thermodynamic (al) two-dimentional stable state is:

$Q=\frac{{2P}_a}{{\mathrm{\πr}}_0^2}{e}^{\frac{-2(x^2+y^2)}{r_0^2}}=\frac{2\mathrm{Pal}}{{\mathrm{\πr}}_0^2}{e}^{\frac{-2(x^2+y^2)}{r_0^2}}$

Can obtain ktp crystal interior temperature distribution curve under different luminous powers according to following formula.Thermoisopleth is oval in the crystal cross section, temperature gradient minimum on x axle and the y axle, the temperature gradient maximum on the crystal diagonal; The temperature gradient of crystal increases along with fundamental power density and becomes big.And frequency multiplication KTP biaxial crystal is to cut by the optimum Match angle that normal temperature calculates down, and the temperature rise meeting changes the principal refractive index of light wave in crystal in the crystal, and three ripple mutual effects produce phase mismatch in the crystal thereby cause, and causes shg efficiency to reduce.Because semi-conductive 808nm luminescence spectrum is along with temperature raises, per 3 ℃ of drift values that increase 1nm are arranged.This drift value reduces the effective pumping light power of the semiconductor of the strong absorption line absorption of 808nm in the YAG absworption peak, causes laser power to descend.Determine that for fundamental frequency light, working temperature can make laser power increase more than 20% when being increased to 25 ° by 23 °.The temperature of therefore accurate control cooling system all is very necessary for efficient that improves system and stability.Because the electric injecting power of semi-conductor array system is very high, reaches several kilowatts of magnitudes.So a water-cooling system of overlapping greater than 5 kilowatts has been assembled in design.Consider accuracy control over temperature, adopted the mode of constant refrigeration and control heating.Its schematic representation of apparatus is seen accompanying drawing 3, and this water-cooled thermostat system technical indicator is as follows:

Refrigerating capacity: greater than 5kW.

Temperature regulating range: 10～30 ℃: accuracy of temperature control: ± 0.5 ℃.

Flow: greater than 8 liters/minute, the flow scalable, adjustable range is greater than 5 liters/minute.

Hydraulic pressure: about about 3.6 kilograms/square centimeter, maximum 4.3 kilograms/square centimeter.

Water tank adopts stainless steel material, and uses multi-filter.

Claims (3)

1. A kind of high power semi-conductor pumping green laser method for generation and device is characterized in that:

   1. it is one group by 5 semiconductor device arranging at the circumferential equilateral pentagon of the horizontal section of Nd:YAG laser crystal, and it is equal 16 groups of row vertically, form high power semi-conductor pumping assembly, the corresponding configuration water-cooling channel.
2. 2. adopt the resonant cavity of recessed-Ping cavity configuration of optimizing, the concave mirror radius of curvature is 1.5m～2.2m.
3. 3. the position of and axis vertical at vertical two ends of Nd:YAG crystal, two acoustooptic Q-switchings are set respectively, dispose water-cooling channel simultaneously, be used the high-efficiency water cooling constant temperature system, frequency-doubling crystal is cooled to 6.0 ℃, adjust shake angle (about 0.7 °) in the chamber of frequency-doubling crystal simultaneously, adjust the modulating frequency and the impulsive synchronization time of acousto-optic modulator, acquisitions repetition rate is that 20.3kHz, pulse duration 135ns, average power are that high power, the high repetition frequency green glow (532nm) of 108W exported.