Nonlinear absorption measurement of UV dielectric components by pulsed top-hat beam thermal lens

A sensitive pulsed top-hat beam thermal lens technique has been used to measure the nonlinear absorption coefficients of fused silica, CaF2, and MgF2 bulk materials, as well as LaF3/MgF2 layer pairs at 193 nm. The measurement values for the bulk materials are in agreement with the literature values. In case of LaF3/MgF2 layer pairs the absorption behavior of single MgF2 and LaF3 layers, (1L3H)7, (3L1H)7, and (LH)20 LaF3/MgF2 multilayers, all deposited on CaF2 substrate, was evaluated. It was found that the nonlinear absorption coefficient of the LaF3/MgF2 multilayers was controlled by that of the LaF3 layers and was estimated to be approximately 4-7 × 10−7 cm/W.