High Efficiency Of Yb：YAG Surface Gain Slab Lasers

Solid state lasers with high average power are compact,efficient,robust,and have good beam quality.There are many applications including military areas,industry and medical treatment.High power lasers,with a rob gain medium,may have a limited output characteristics due to the thermal effects.Slab and thin disk lasers are more suitable to be the gain medium of a high power laser because of the reduction of thermal gradient.A novel surface gain slab laser is designed to achieve a high power and high efficiency with the qusi-three-level Yb:YAG laser crystal.In this paper,the factors affecting the output of surface gain slab laser are analyzed theoretically and experimentally,and a pumping system with stripe-mirror-polarizer composite combining is designed,so as to realize the efficient output of Yb:YAG surface gain laser.It is the Yb:YAG crystal that more suitable for high power continuous laser operation by comparing with the characteristics of Nd:YAG and Yb:YAG crystals.Moreover,the methods to restrain ASE or PO are simply analyzed in order to avoid their influence.Furthermore,to ensure the bigger beam filling ratio inside the slab,according to theoretical analysis of fill factor,the cutting and incident angle are 45°and 22°,respectively.In addition,a pumping system with stripe-mirror and polarizer composite combining,was designed to improve the pump power density to 43 kW/cm~2 and 50 kW/cm~2 in large and small pump structures.The output power and optical efficiency of lasers is simulated with the best analysis parameters.The gain medium size of lasers and amplifiers are 120mm×28mm×2mm and 67mm×11mm×1.7mm,respectively.For laser oscillator,the output energy reaches20.54J,and the optical efficiency is up to 50%at low repetition.When the pump power is 25kW,the output power reaches 7.01kw and the optical efficiency is 28%.For laser amplifier,the pump and seed power are 11kW and 200W,the single and double-pass extraction output power is 1.6kw and 2.6kw,and the optical efficiency is12.8%and 22%.The transmitted wave front of lasers and amplifier are 0.85μm and1.3μm,respectively.Results show that the output beam is of good quality.The experimental results are consistent with the theoretical analysis.If the relevant process is further improved,the surface gain slab lasers are expected to achieve higher power and higher efficiency.