High-sensitivity absorption spectroscopy of lithium niobate crystals in the near and mid infrared regime

Lithium niobate (LiNbO3) possesses several useful electrical and optical properties, making it a suitable material for a wide range of applications like electro-optic modulators and nonlinear-optical devices. The latter are operated in the transparency window of LiNbO3 between 450 and 4000 nm wavelength. The availability of high-power pump lasers has made nonlinear frequency conversion processes more and more effective. With increasing pump powers, however, even weak absorption due to residual impurities or crystal imperfections may lead to thermal or mechanical malfunction of the devices. Proper characterization of the materials is of scientific interest and practical relevance.