Research On All-solid-state Laser Nonlinear Frequency Conversion And Thermally Boosted Pumped Technology

With the maturity of the diode pumped solid state lasers, it has become one of themost important research point of the optics field. In this paper we research on all solidstate laser and nonlinear frequency conversion techniques, including ultraviolet laser,yellow laser, optical parametric oscillator and a new thermally boosted pumpedmanner, some new architecture and conpect were given here.The main contents and key innovative points are as follows:1.All-solid-sate ultraviolet laserThe266nm and355nm ultraviolet laser were researched, the compact and efficient355nm laser was realized without additional focusing system by using the thermallens of Nd:YAG crystal itself, with an input pump power of28W, modulatedfrequency at10kHz,1.65W ultraviolet355nm laser was obtained with single pulseenergy165μJ，pulse width6ns, corresponding peak power of27.5kW, optical tooptical （1064nm to355nm） efficiency is20.4%. In order to improve the conversionefficiency. We proposed the secondary summing frequency techniques to make therest power of1064nm and532nm of the first summing frequency sum frequencyagain. With an input pump power of25W,2.7W third harmonic radiation at355nmwas obtained. The optical-to-optical （1064nm to355nm） conversion efficiency was43.5%. To further improve the optical to optical efficiency from1064nm to355nmlaser, a concave reflection mirror was used to focus the laser of1064nm and532nminto two third harmonic optical crystals, which avoids the chromatic aberration oftraditional focusing lens effectively. Finally, the optical-to-optical （1064nm to355nm）conversion efficiency was up to47.4%.A compact diode end pumped Nd:YAG extracavity frequency conversion266nmultraviolet laser was realized with a short fiber coupling and short optical resonatorsturcture, with the pumped power of25W and modulation frequency10kHz,0.85Wultraviolet266nm laser was obtained, the pulse width was6ns, the optical-to-optical（1064nm to266nm） conversion efficiency was13.7%.A laser diode side-pumped Nd:YAG266nm ultraviolet laser was also researchedin this paper. To improved the beam quality and increase the conversion efficiency, azigzag cavity was used in this laser, when the pumped current was19A, modulatefrequency is5kHz,16W532nm green laser was obtained with the beam quality factor of5, with the extra-cavity frequency conversion of BBO crystal,2.1W ultravioletlaser266nm was obtained with a optical to optical （532nm to266nm） conversionefficiency was13.13%.2.All-solid-state yellow laserA new configuration of589nm yellow laser with a single LD pump source andcoaxial double crystals was proposed in this paper. When the incidence pump poweris1.5W,54mW yellow laser at589nm was obtain, the optical to optical conversionefficiency is3.6%, the laser long term instability was about5%. An orthodox methodfor589nm laser was also employed under the same condition, only15mW yellowlaser was obtain. The configuration of single pump source and coaxial double crystalsis compact and flexible which can be used in many sum frequency laser.3.All solid state continuous-wave tunable eye-safe and3-5μm mid-infrared laserTemperature and grating period turning curves of PPLN-OPO were calculated.Experimental tuning range were1401¹513nm for near infrared eye-safe signaloutput and3.66⁴.22μm for mid-infrared idle output, which matched theoreticalcurves well. When the LD pump power was17.1W, the maximum signal outputpower was2.21W at1500nm, with a conversion efficiency of12.9%. For the idleoutput, it was960mW at3.66μm, the conversion efficiency was5.6%.4All solid state thermally boosted pumped lasersA high efficiency1064nm Nd:YVO₄laser thermally boosted pumped from highStark sublevel of ground state to upper-laser-level by a914nm Nd:YVO₄laser wasdemonstrated. To overcome the shortcoming of low absorption in this pumpingscheme, three possible means-increasing temperature, doping concentration andlength of the Nd:YVO₄crystal-were adopted and compared in detail in theexperiments. The experiments show that using longer gain medium with properdoping concentration should be the most promising method to ensure the absorptionand high efficiency. The maximum1064nm output power of2.27W was achievedwith a1.0%doped,10mm long Nd:YVO₄crystal at the temperature50°C, leading toa efficiency of79.9%with respect to the2.87W absorbed914nm pump power. Ahigh-efficiency1342nm Nd:YVO₄laser thermally boosted pumped at914nm isdemonstrated. An a-cut8mm length Nd:YVO₄crystals-1.0-at.%doped was choosenin the experiment. Finally,0.86W of1342nm laser output was obtained with1.82Wabsorbed pump power. Corresponding slope efficiency of65.4%. Based on the880nmthermally boosted pumped Nd:YVO₄self-stimulated Raman scattering laser was experimental demonstrated, the experiment shows that compared with808nm pumpedmanner the in-band pumped can reduce the heat deposition in the Nd:YVO₄crystalsand improve the optical conversion efficiency of self-stimulated Raman scattering.