High power femtosecond regenerative amplifier based on Yb: CaYAlO4 dual-crystal configuration

A Yb: CaYAlO4 based thermal insensitive regenerative amplifier with dual crystal configuration for extending gain spectra is proposed and executed for the first time. By orthogonalizing the orientation of two a-cut Yb: CaYAlO4 crystals, the Q-switched spectrum with a central wavelength of 1035 nm and a spectral full width at half maximum of 15.4 nm is attained, which is 1.5 and 1.6 times of the Q-switched spectral bandwidth with π and σ polarization, respectively. The pulse energy of the seed is amplified to 1.5 mJ at 1 kHz repetition rate. By varying the repetition rate of the regenerative amplifier, the amplified power can exceed 10 W at the repetition rate of 20-800 kHz. Thanks to the design of the thermal insensitive dual crystal RA cavity and excellent thermodynamic properties of the Yb: CYA crystal, the amplified laser beam is near diffraction limit with an M2 value of 1.07×1.07. A compressed pulse of 218 fs with 92% overall efficiency is realized. The presented results show that Yb: CaYAlO4 crystal has great potential to generate high energy and high-power femtosecond pulses with sub-120 fs pulse duration.