Research On Controllable Thermal Management Of Solid-state Lasers Based On Dual Wavelength Synthetical Pumping

All-solid-state laser is always highly rated because of its high efficiency, high beamquality and compact structure. However, all kinds of harmful thermal effects limit theoutput performance of solid-state laser in many aspects. According to the researchexperience before, the generation of useless heat is largely decided by pumpingmethod and pumping character.Considering the superiority and shortage of traditionalLD pumping and in-band pumping, we state the concept of synthetical pumping. Bymodulating the proportion of the two different pump wave, one can not only controlthe heat generation of laser but also find a balance point of output and thermal load.Thus on one hand we can realize the controllable thermal management in solid-statelaser, on the other hand it’s easy to achieve laser performance with high power, lowthermal load and high beam quality in DPSSL with an ordinary gain media.In this dissertation, collocating880nm and888nm pump wave with808nm as twopumping schemes, we conduct the synthetical pumping laser experiment by using a0.5-at%doped Nd:YVO₄crystal with a length of4mm. We mainly study the outputperformance and the maneuverability to control heat generation by modulating theproportion of power of two different pump waves. The main contents are as follow:1. We performed theoretical analysis on synthetical pumping and simulated theoutput character based on the four-level rate equation. Then we discussed howto determine the optimal proportion and proposed an assessment system（parameter η with a dimension of efficiency） on synthetical pumping laser.2. During the experiment we set several values of pump power. With each fixedpump power we measured the laser output properties when the proportion of808nm pump wave was0%,20%,50%,80%and100%. For the808+880nmscheme, at an input power of20W, when the proportion of808nm was100%we obtained the highest output power of10.85W and highest thermal load of6.69W; when the proportion of808nm was0%we obtained an output power of8.31W and a thermal load of2.43W. The difference of output power （2.54W） ofthe two extreme cases was small while the difference of heat was large （4.26W）when the pump proportion changed. This could realize the control of heatgeneration by modulating the pump proportion with a relatively high outputpower guaranteed.3. We obtained the experimental curve of parameter η through the experiment data. According to the curve the maximum value of η was0.5when the pumpproportion of808nm x reached⁴1%, which was coincide with the value ofsimulation. At this point, the oputput power and the thermal load are9.57W and3.89W respectively. Comparing to880nm pumping the thermal load ofsynthetical pumping decreased41.85%just with a11.8%output loss, while theoverall conversion efficiency was15.16%higher than880nm pumping, whichdemonstrated the validity of theoretical analysis on the assessment system.4. The data of808+888nm scheme was mainly used to be as a control group. Theresults indicated that the880nm wave was more siultable to be used insynthetical pumping to control the heat generation due to a relatively highabsorbing efficiency. The difference between the values of η with the twopumping schemes also demonstrated that the parameter η is practically rational.According to the results of experiments, the significance of assessment system onsynthetical pumping laser is clear that, for any solid-state laser, we can balance theoutput power and thermal load perfectly through this way. The essence of all we did,such as exploring the optimum pump proportion and realizing the controllable heatmanagement, is to improve the whole effective availability of pump wave in anysolid-state laser system.