Development of Stable Seed Pulses for Optically Synchronized Optical Parametric Chirped-Pulse Amplifier Pumping

抄録

In this paper, we report the development of optically synchronized seed pulses to achieve low-jitter pump pulses for optical parametric chirped-pulse amplification in a petawatt-class laser system. The 1064 nm pulses are generated from Ti:sapphire oscillator pulses by soliton self-frequency shift in a photonic crystal fiber (PCF). The center wavelength of the PCF output spectrum is kept at 1064 nm using a newly proposed feedback control system. This is performed by rotating a half wave plate automatically by an amount that depends on the extent of center wavelength shift. The center wavelength is stable, with a fluctuation of less than 0.02% (root mean square). The stabilized pulses are amplified to 150 mW at 80 MHz by four Yb:fiber amplifiers and stretched to 1.2 ns by a fiber Bragg grating. As a preliminary result, the stretched pulses are amplified in a diode-pumped Nd:YAG regenerative amplifier to 135 mJ at 1 Hz.