Influence of energy transfer upconversion on thermal lens of Nd:YVO _4 bounce laser amplifier

摘要

Detrimental thermal effects affecting optical performances of a Nd:YVO _4 bounce laser amplifier are investigated numerically under small-signal gain conditions. Thermally induced lens is stronger due to the increase of the fractional thermal loading with the pump irradiance, which is caused by the Auger energy-transfer upconversion (ETU). At a pump power of 100 W, the focal length of the thermal lens (TL) is comparable to the length of the laser crystal and is shorter than without Auger ETU by a factor of 3 and 2.5 in the bounce plane and, respectively, in the plane orthogonal to bounce. This deleterious influence of Auger ETU on the TL of the bounce laser amplifier can be alleviated by the increase of the pump spot area and by the mismatch between the diode pump spectrum and the absorption band of the crystal.