Femtosecond laser based on Yb:KYW crystals with suppression of spectral narrowing in a regenerative amplifier by spectral profiling of the pulse

This paper describes a femtosecond laser regenerative amplifier based on two Yb:KYW crystals with direct longitudinal pumping by powerful linear arrays of semiconductor injection lasers having fiber output. To prevent spectral narrowing during amplification and the corresponding lengthening of the amplified pulse when it is compressed, a combination of two Yb: KYW crystals were used, with the spectral maxima of the amplification shifted relative to each other and with spectral profiling of the amplified radiation. The mean power of the laser before compression reached 12 W at a pulse-repetition rate in the range 50-500 kHz and a spectral width of 10 nm, which is about a factor of 2 greater than the spectral width without profiling. The pulse width after compression in the compressor equalled 182 fs, while the mean power exceeded 8 W. The laser system thus developed can be used as a source of powerful femtosecond light pulses for the microprocessing of materials and for biomedical applications. (C) 2013 Optical Society of America.