Abstract
Thermal effects are the main obstacle to getting high power and good beam quality in diode end-pumped solid-state lasers. In this work, a theoretical investigation of thermal effects in single and dual end-pumped solid-state lasers is carried out using finite element analysis (FEA) for a selected number of widely used laser producing materials, namely, Nd:YAG, Yb:YAG, and Nd:KGW. Crystals with different dimensions are also investigated both in single and in dual end-pumped configuration. Finally, the effect of using composite crystals on thermal lensing is investigated. An experiment to measure the thermal focal length for two different crystals was carried out and a comparison with FEA computed focal length of the thermal lens is made. In all cases studied in this work, results show clear effects of thermal lensing with some differences depending on crystal type, pump power, and size.
Highlights
Obtaining high power output in diode pumped solid-state (DPSS) lasers with good beam quality is limited by the thermal effects in the laser crystal which induce thermal lensing and losses due to depolarization and cracks in the laser crystal [1,2,3]
A fiber-coupled diode laser is used to pump the laser crystal longitudinally, and the end of the fiber is coupled to microlenses to adjust the pumping beam shape to match the mode TEM00 of the laser resonator to make use of all the output power of the diode laser [4]
We carried out a finite element analysis study for three common types of solid-state laser crystals, namely, Nd:YAG, Nd:Y3Al5O12, Yb:YAG, and Nd:KGW (neodymium-doped potassiumgadolinium tungstate crystals (Nd:KGd(WO4)2)
Summary
Obtaining high power output in diode pumped solid-state (DPSS) lasers with good beam quality is limited by the thermal effects in the laser crystal which induce thermal lensing and losses due to depolarization and cracks in the laser crystal [1,2,3]. For these purposes, a longitudinal pumping configuration was developed which is called end-pumped solid-state lasers which give high quality output beam and efficiency in comparison to side pumped lasers. We carried out FEA calculations for a selected number of laser producing crystals with different dimensions for a number of sizes and pumping parameters; we discussed the results and compared some of them to the actual experimental setup which gives us a better understanding of the numerical results and their deviation from the real measurement
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