RESUMO
Yb-doped materials, due to their high saturation fluence and consequently their low gain, represent a challenging choice for high-energy amplifiers. In this Letter, we study two original amplifier designs adapted to a large number of passes capable of operating in the 100 mJ energy range at repetition rates up to 100 Hz using Yb:CaF2 crystals as active media. Amplification geometries based on double-head active-mirror configurations are presented. We confront two alternative strategies suitable for amplification of large beams: regenerative and geometrical multi-pass amplifiers. This Letter consists of finding the pivot point, allowing us to discriminate the specific interest of each strategy. We present compensation methods of the thermal lens adapted to each amplifier configuration with and without cavity, and we demonstrate that despite similar laser heads and pumping conditions, the thermal lens impacts differently the optimal performance for multi-pass or regenerative strategy. We perform amplification up to 66 mJ pulses at 10 Hz with the regenerative amplifier and 52 mJ at 100 Hz with the multi-pass amplifier.
RESUMO
We propose and demonstrate an architecture that achieves passive coherent combination of two femtosecond fiber chirped-pulse amplifiers. The setup consists in the use of a well-balanced amplifying Sagnac interferometer. The experiment shows that the temporal, spectral, and spatial qualities of each beam are retained, with the generation of 250 fs pulses at 35 MHz repetition rate, an uncompressed average power of 10 W, and a combining efficiency of 96%. The behavior of this architecture in the presence of high accumulated nonlinear phase is investigated.
RESUMO
We present a diode-pumped regenerative amplifier based on an Yb:CaF(2) crystal optimized to produce short pulses for various repetition rates ranging from 100 Hz to 10 kHz. The shortest pulse duration generated is 178 fs, and the corresponding energy is 1.4 mJ before compression (620 microJ after), at a repetition rate of 500 Hz for 16 W of pump power. The bandwidth is 10 nm centered at 1040 nm. Higher repetition rate regimes have also been explored, allowing an optical-to-optical efficiency up to 10% at a high repetition rate.
