Parameters optimized for optical thin film weak absorption testing set-up

The weak absorption characteristic of thin film is an important parameter to estimate optical quality. Especially for high-power laser, even the very weak absorption in thin film is high enough to result in catastrophic damage. Thus, it is necessary to measure the mean and local absorption of the optical thin film accurately, fast and in-situ. The surface thermal-lens technique is one of the available methods to measure the weak absorption. It developed from the optical beam deflection technique, with the relaxation for requirements of the measurement layouts and the same measurement precision. Based on a self-built experiment setup, the stability and the linear responsibility of the weaken absorption signals of the optical thin film were measured with variational parameters, which offered the key parameters for solidifying layouts. The elementary experiment of weak absorption has been tested based on the proposed system.