Femtosecond oscillator on Yb:KYW crystal pumped by laser diode with fiber output

A femtosecond laser based on an Yb:KYW crystal with direct longitudinal pumping by a high-power semiconductor injection laser with a fiber output is described. Femtosecond pulses were generated in the self-longitudinal-mode-locking operating condition due to the use of a semiconductor saturable absorber. The average power of the oscillator was as high as 3.5 W at a central wavelength of 1035 nm, the pulse length and pulse repetition rate being 200 fs and 85.5 MHz, respectively. The product of the pulse length and the radiation spectrum width was 1.3 times higher than the theoretical limit for the pulse shape described by the function sech². The designed master oscillator can be also used as a stand-alone source of femtosecond radiation pulses for material microprocessing and primary source for femtosecond laser amplification systems.