The heat in laser of whole solid state controls overview

The heat government issue of working medium basically behaves laser to be in in working material the fuel factor problem of pump riverside process: While pump riverside source offers generation laser place to require energy to solid laser medium, useless heat is caused in medium. Work to last, must eliminate these useless heat in time from inside laser medium (medicinal powder hot) , form " fuel factor " . The output that restricted laser already is average power, at the same time distortion brings about quality of laser light beam to drop, make the brightness that outputs laser is reduced. And the heat government issue to pump riverside source basically is aimed at laser diode array, its application improved the efficiency of solid laser system greatly, however, want to be working temperature control inside relatively narrow range, need has more perfect heat to control a system, this and laser of flashlight pump riverside are different, in system of riverside of end panel pump, come through temperature the output wavelengh of harmonious laser diode, absorb spectral line photograph what make to match with laser peak value; Pass TE frigorific implement the temperature that controls array, maintain gotten wavelengh, this kind of method is very effective to small-sized laser, in old system, can use liquid cooling loop to maintain semiconductor laser not to get normally the influence of environmental temperature. Nevertheless refrigeration efficiency won't exceed 1 normally, nod power input to be equivalent to needing pilot quantity of heat, accordingly, in producing big caloric system, the electric power of the input is quite high, refrigeration efficiency is very low at the same time, this is a very big question, challenge of a huge is on the technology. Heat of laser job medium manages a problem with Nd: YAG crystal is exemple, nd: YAG crystal is to apply at present most, have medium of representative job of a kind of solid most, it belongs to system of 4 energy level, if pursue,L place is shown. Fig.

1The Energy Structure Fo A Nd:YAG becomes Nd: YAG crystal gets the drive of outside energy (pump riverside) when, the particle that is in ground state L to go up goes to transition energy level 4 on, energy level 4 go up the life of particle is extremely brief, very fast hot relax pleaseds metastable energy level 3 on. Energy level 3 go up the life of particle is longer, and the energy level below room temperature 2 on number of particle yard up is close to Yu Ling. Because this is very easy in energy level 2 and 3 between form number of particle yard up to invert, the 3 particle transition that go up reach energy level energy level 2 on form laser oscillation. The 2 particle that go up heat up energy level very quickly relax pleaseds ground state energy level 1, in order to maintain energy level 2 on number of particle yard up is approximately 0, laser threshold value is very low. From 1960 body of stretch of the first laser puts the solid laser of riverside of electric lamp pump to be born, people is having indefatigable accuse and denounce at a meeting with the harmful fuel factor that accompany laser and arises. Reducing useless hot field to had fetched significant gain, but did not solve completely. Baconian rise, basically had the job of two respects: The laser of 1 useless hot whole solid state that reduces the generation inside working medium as far as possible uses semiconductor laser diode (LD-laser Diode) replaces medium of laser of solid of flashlight pump riverside, as a result of pump Pu Guang and absorb the belt is complete match, reduced useless heat greatly, but the energy level from YAG (graph 1) can see, as a result of quanta blemish, suffer stimulate voice to absorb etc, useless heat still should produce in working medium. Developed technologies of a variety of riverside of low hot pump then (all sorts of method be called by a joint name that remove the useless heat that quanta blemish causes further are technology of riverside of low hot pump) the no use in reducing laser job medium further is hot. Be like: A is used allow system of 3 energy level to be able to reduce quanta blemish, but wait to density of pump riverside power, uniformity have very high demand, among them the famousest is Yb: YAG crystal; Technology of riverside of B direct pump, ground state particle direct pump riverside arrives on laser energy level 3, and do not pass energy level 4; C heat is aided promote a technology, the Situokesi drive of the heat on ground state direct pump riverside goes to the particle on energy level the energy level on laser 3; D radiate is balanced, decrease as far as possible enter working medium no use to heat up, the balance that maintains laser and optical pump light intensity. 2 fall in existing technical condition, the useless heat in laser medium can decrease as far as possible only, and cannot eliminate completely, decrease, the bad influence that compensates useless thermal conductivity to send already developed a variety of technologies to decrease at present, the adverse effect that compensates useless heat to cause, be like: A.

Make thermal current and laser direction consistent, hot distortion reduces B to the influence of quality of laser light beam.

Heat up the adverse effect that cause to reduce no use further, a variety of effective practical technologies developed on the program that to laser riverside of the geometrical appearance of working medium, pump cools and structural design, reasonable design is impure at the same time chroma, pump Pu Jiang is spent and distributing, reduce hot gradient to wait. Include to use round stick among them, tubal shape, attrib wattle, dish piece, fiber-optic wait, heat up at coming loose effectively with benefit, current relatively outstanding basically have the following kinds of kinds: A.

The laser of round strong record of LD pump riverside, used LD pump riverside to had reduced the useless heat that enters working medium greatly, but as a result of quanta blemish, quanta efficiency and go up the performance that the useless heat that the loss such as changeover causes affected solid laser badly still. Want to obtain laser of quality of high average power, efficient, tall beam of light to output, first requirement is the uniformity that should assure pump riverside. This involves pump riverside structure, intensity, the geometrical appearance of working medium, impure chroma and chroma distributing etc; It is to try to eliminate or compensate heat to send birefraction next; Rising fight strain crack side, job of thermal capacitance mode obtained the most apparent effect. With be not spherical lens to be able to compensate hot distortion partly, be aimed at the pump riverside power that some secures especially; As a result of smooth effect direct ratio at the gain inside antrum and loss than, because this uses the working means of tall gain, low distortion,will be helpful for increase output average power. B.

High average power is fiber-optic laser, compare with traditional solid laser, the " of bulk of ／ of " watch area of the working medium of fiber-optic laser is compared very those who compare medium of other lump job is big 2- - ~3 quantitative class, medicinal powder hot result is favorable; Laser mode is decided by D of fine core diameter and numeric aperture NA, the no use in getting medium is affected hotly; Fine core diameter is very small, realize riverside of even pump of high power density easily; C.

Thermal capacitance laser, thermal capacitance laser is intermittent job, medium of incorrect during pump riverside and laser blast off job is cooling, working medium " store can " , ability is cooling to working medium during laser launchs the intermittence after stopping, enter next loop next, because intermittent time is frigorific, can use natural wind cold, integral structure is reduced, suit for military use particularly. C.

Use retreat slant recycle of compensation, loss enhance output power; D.

Reasonable antrum design heats up an influence with compensation. In in antrum design can be adopted below little output power win single vertical standard, single horizontal standard, the laser of quality of tall beam of light of higher average power, this is to compare sufficient, theoretic more mature job; E.

Use thermal capacitance pattern the job, press stress design to raise working medium threshold value of heatproof strain crack; Because the emissive wavelengh of diode follows temperature happening drift,heat of source of riverside of pump of Figure2 The Sketch Map Of Microchannel manages a problem, be about to undertake to pump riverside diode lukewarm accuse, in order to assure pump riverside efficient, and LD power is in increase ceaselessly, freeboard is average of power laser come loose effectively heat is a very serious problem. The tall heat flux that appears possibly in small system to LD it is deadly, the heat flux of the LD embattle that uses at present is 100 made of baked clay class / Cm2, as the addition that outputs power, the quantity of heat that needs dissipation also increases necessarily, the cooling technology that uses a convention however should make so tall heat flux drops off inside short time is not actual almost; On the other hand, the dependability that LD works is very sensitive to temperature, temperature is average every change 1 ℃ wavelengh can change 0.

3nm, at the same time dependability can drop. Must want in development, development consequently mature arrive to come loose goodly hot method, ability assures the dependability of the product and apparent. Be changed as a result of the miniaturization of parts of an apparatus, miniature and compositive change, what use medicinal powder heat and cooling method must ask to have come loose compact sex, dependability, flexibility, high the characteristic such as thermal efficiency. From tiny electron yuan the angle that parts of an apparatus uses at present looks, commonly used method basically has: Heat up or come loose naturally cooling, compulsive method of means of means of heat or refrigeration of cooling, liquid, refrigeration, dredge means, hot segregation and PCM temperature control, hot method comes loose burgeoningly to still have small passageway on international, use change small chamfer of the technology group technology and sparge technology are waited a moment. Already used at laser refrigeration technology: Empty cold pattern, means of immersion type liquid cooling, single-phase, photograph changes liquid cooling means includes millimeter - micron class " small passageway " means) , the TEC means of groovy dimension, sparge refrigeration means (lab phase) , can apply those who go up in laser to come loose to what mature quite at present only hot structure undertakes introductory: Means of refrigeration of small passageway of Figure 3 The Sketch Map Of Micro-groove1 passes those who raise radiator to come loose hot area, rise medicinal powder thermal efficiency. Coefficient of convection heat exchange basically is mixed of dimension of velocity of flow, feature, density, fluid conduct heat the element such as coefficient, thermal capacitance is concerned. Increase velocity of flow, increasing diagnostic size is to increase conduct heat the commonly used method of coefficient, at the same time the fluid is when vigorous turbulent flow heat exchange effect is best. 2 small chamfer group become cooling means is in odd a laser diode array base piece on compose builds wool subtle chamfer group change unit extraction heat (miniature evaporator) . Corresponding at laser diode array, the parallel connection that uses many miniature evaporator forms the array type in little space to take hot unit to undertake extraction heat, build small fluid of shunt type or rally pattern and return of transport of quantity of heat, and passive type or active condenser (Leng Duan heat is heavy) , if pursue,3 are shown. Laser of brief summary whole solid state becomes laser technology research, developing not only a popular task, and had won many fundamental application, but in use LD pump riverside and solving solid laser completely " useless heat " problem, the development that movement of the high average power that should achieve project meaning to go up, tall stability relies on technology of riverside of working medium, LD, pump to wait even. CNC Milling