| Abstract [eng] |
Laser-matter Interaction: Evaluation of Non-radiative Losses by Holographic Probing of Dynamic Thermal Lens The main interest in this paper was the dynamic processes after laser induced excitation of transparent media in the range from nanoseconds to microseconds. The visualization of the processes was achieved using digital holographic microscopy in pump-probe experimental setup. In order to reach the delay values of interest two independent laser sources were used. The lasers were synchronized and electronic delay line had to be implemented between pumping femtosecond laser and probing nanosecond lasers. In the experiment 1,6 µJ energy S polarized light impulse of 380 fs duration and 1030 nm central wavelength was used to excite a fused silica sample. The dynamic response of the excitation from 20 fs to 12 µJ was obtained and recorded. The process in the range 0,1-12 µs was identified as a dispersion of heat, and was observed as dynamic thermal lens. In order to evaluate the residual heat in the exited region the experimental data was later compared to results of a simple numerical simulations of heat propagation using finite difference method. Both the experiment and numerical simulation provide similar time dependency of phase shift decay. Using the method of least squares and changing the amount of heat used in modeling, energy of minimal error between simulated and experimental data was evaluated. This way, for the first time, the residual energy deposited in the material after single shot excitation was evaluated photographically. The evaluated value 108±8 nJ is equivalent to 6,75% of the initial impulse energy used for excitation. |
