We reported an active multipass stretcher which can deliver chirped pulse with high energy, adjustable duration and high beam quality. The stretcher system is based on a Martinez stretcher and a regenerative amplifier. The stretched pulse duration can be adjusted without changing the layout. With 1 ns stretched pulse output per roundtrip, chirped pulse with more than 10 ns can be obtained after several round-trips. A laser amplifier is introduced into the cavity to compensate the energy loss caused by the diffraction efficiency of gratings, and several millijoules pulse energy can be obtained after stretching and amplification. Benefit with the advantage of the regenerative structure, the stretched pulses have an excellent beam quality with M2 of 1.1. This novel stretcher is significant for high peak power laser systems.
Previous research on achieving the alignment of compression gratings has mainly focused on the parallelism of the gratings. We propose a promising method to achieve parallelism and especially accurately adjust the grating to its optimum working angle to achieve dispersion compensation. A spectrometer and a precisely adjustable mirror pair are cooperatively used to measure the wavelength of the light diffracted by the grating, satisfying the Littrow condition. Meanwhile, the tiny slit of the spectrometer can decrease the grating-tip and in-plane rotation error during the alignment procedure. Using this technique, the residual phase of the compressed pulse is optimized and the compressed pulse duration is 25.4 fs, which is 1.06 times that of the Fourier-transform-limited compressed pulse.
We report a generation of 10.6% conversion efficiency near 1053 nm first order Stokes pulse in stimulated Raman
scattering pumped using 800 nm Ti:sapphire based femtosecond pulses that are stretched to 460 ps, obtained by use of a
single pass ethonal Raman shifter. The Stokes pulse almost maintains the bandwidth of the pump and is compressed to
~10 ps using a mismatched grating-pair. The spectral characteristic of the Raman pulse is calculated and the results
explain the observed transient features.
We demonstrate high amplified spontaneous emission (ASE) contrast pulses in a Nd:glass laser system based on the hybrid double chirped pulse amplification (double CPA) scheme. By an OPA temporal cleaning device, ~100 uJ/46 fs/ 10<sup>11</sup> clean pulses are generated and amplified in the next Nd:glass laser. After compressor, >150 mJ/~0.5 ps/1 Hz pulses can be obtained. The ASE temporal contrast of amplified pulses is ~10<sup>11</sup> with energy gain ~2.5×10<sup>4</sup> in the Nd:glass amplifiers.
Comb-like supercontinuum generation is investigated with dual-pulse filamentation in air. The period of spectral
fringes varies with the time delay between collinearly propagating pulses. The comb-like supercontinuum may be a
potential tool for optical remote sensing.