| Abstract [eng] |
In this dissertation, sub-picosecond hybrid laser systems are investigated, which are based on an all-in-fiber seed source and end-pumped double-pass Yb:YAG amplifier cascade. These laser systems could be widely used in the science, industry, and military sectors. A numerical model for the Yb:YAG amplifier was presented and experimentally verified – optical amplification, beam degradation due to thermal effects, and gain narrowing effects were verified. Three different laser systems were experimentally demonstrated based on the modeling data. These systems featured such laser parameters: (1) pulse energy 104 uJ, pulse repetition rate 200 kHz, pulse duration 764 fs; (2) pulse energy 1 mJ, pulse repetition rate 14 kHz, pulse duration 815 fs; (3) pulse energy 35 uJ, pulse repetition rate 1 MHz, pulse duration 318 fs. It was experimentally demonstrated that spatial filtering and amplification of the circular polarization radiation minimizes the beam degradation due to the thermal effects in such amplifiers. The last chapter of the dissertation focused on the minimization of power losses due to the depolarization effect in the additional Yb:YAG amplifier cascade. An innovative depolarization compensation method using a spatially variable waveplate was presented. Power losses were reduced from 18% to 3%. In such a system, 116 uJ pulse energy, 1 MHz pulse repetition rate, and 441 fs duration pulses were achieved. |
