Highly Efficient Solar Pumped Nd:YAG Solid Laser

Solar-pumped solid-state laser is a new type of solid-state laser that uses solar radiation as the pump source to directly convert wide-spectrum sunlight into narrow-spectrum laser.Compared with the traditional solid-state lasers,the solar-pumped solid-state laser is low cost,has less energy conversion steps,therefore good prospect in space and military applications.Up to date,the solar-pumped laser can achieve the laser output in the form of:solid-state laser,fiber laser,and semiconductor laser.In this paper,the research focuses on the most efficient and most widely studied solar-pumped solid-state lasers and the new type of solar-pumped solid-state laser amplifier.This paper summarizes the research significance of the solar-pumped lasers,related applications and research progress.A two-stage concentration structure formed by a Fresnel lens and a gold-plated conical cavity with a liquid light-guide lens is presented.The characteristics of the gain medium suitable for the solar-pumped solid-state laser are analyzed.Nd:YAG crystal is selected as the gain medium,due to the high degree of absorption spectra matching the solar spectrum,low pumped threshold and high thermal conductivity.The geometry and size of the crystal is optimized by the simulation.A theoretical model and the energy conversion of solar-pumped laser are discussed.The threshold,slope efficiency and output power of solar-pumped solid-laser are derived.Gain formula and output power formula of solar-pumped solid-state laser amplifier are deduced.The optical design software ZEMAX and laser cavity simulation software LASCAD are used to simulate the performances of the solar-pumped Nd:YAG solid-state laser with a gold-plated conical cavity and a liquid light-guide lens.In addition,a high efficiency and high power solar-pumped Nd:YAG solid-state laser using Fresnel and cylindrical lenses array is designed with ZEMAX.The solar-pumped Nd:YAG solid-state laser system is built and outdoor experiments are carried out.When the solar radiation power is 950W/m~2,the maximum laser output is 31.5W,the collection efficiency is 30.58W/m~2 and the solar radiation to laser conversion efficiency reaches 3.2%.The M~2 of the laser is measured as 126.The scheme of kilowatt solar-pump lasers is proposed.As the key subsystem,the solar-pumped solid-state laser amplifier is studied with a composite-slab Nd:YAG crystal.The seed laser propagated along a zigzag path inside the crystal.The length of the seed laser path inside the crystal is 97mm.When the solar radiation power is 900W/m~2,the gain is 1.46.In conclusion,a high efficiency solar-pumped Nd:YAG solid-state laser and a solar-pumped Nd:YAG solid-state laser amplifier are constructed in this paper.The theory and simulation in the design process are analyzed.With the developing of the solar-pumped laser,its applications in space and military is just around the corner.