Suppression of transverse parasitic lasing and amplified spontaneous emission in Ti: sapphire amplifier by polarization-selection pump

摘要

Based on the polarized-dependent absorption characteristic of Ti: S crystals, we propose a method to reduce the absorption coefficient of Ti: S by using a sigma-polarized pump. For Ti: S crystals, the absorption cross section of sigma-polarized pump light is approximately half that of pi-polarized pump light, which reduces the excited state density near the surface of the amplifier crystal, resulting in reduced transverse parasitic lasing and amplified spontaneous emission. The experimental results based on a diameter of 80 mm Ti: S confirmed the proposed method with different index-matched cladding materials [ethanol and bromonaphthalene (BN)]. In the case of an ethanol cladding, the maximum amplified output energies for pi-and sigma-polarized pumping are 20.8 J and 26.8 J, respectively-corresponding to 28.8% energy improvement achieved by the s-polarized pump. In the case of a BN cladding, the maximum amplified output energies achieved by pi-and sigma-polarized pumping are 40 J and 44 J, respectively; this result corresponds to about 10% energy improvement achieved by the sigma-polarized pump. This method can be used in larger size Ti: S amplifiers. (C) 2015 Optical Society of America