Hundred-picosecond narrowband chirped-pulse generation in an Yb:YAG regenerative amplifier using transmission gratings

We have demonstrated a seed source for an optical parametric chirped pulse amplification pumping source through a cryogenically cooled Yb:YAG regenerative amplifier, which can vary the pulse duration depending on the number of passes and generate a very high chirp rate. The Fourier-transform-limited pulse duration of 10 ps was extended to a few hundred picoseconds (109 to 165 ps) to prevent damage to the gain medium in the subsequent high-pulse-energy pumping source, which was seeded by the regenerative amplifier. This was achieved by inserting a transmission diffraction grating pair inside the cavity of the regenerative amplifier. The variable pulse duration could be set between 109 and 165 ps by electronically adjusting the pass number of pulses inside the cavity. The stretched pulse duration and the spectral width as functions of the pass number were characterized by considering the dispersion from the grating stretcher as well as the gain narrowing effect.