Femtosecond oscillator based on an Yb:KYW crystal with direct laser-diode pumping

Abstract

This paper describes a femtosecond laser based on Yb:KYW with direct pumping by semiconductor injection lasers. The Yb:KYW laser crystal was pumped longitudinally by the radiation of two InGaAs semiconductor injection lasers that operate at a wavelength of 981nm. The spatial structure of the radiation of the semiconductor lasers was reshaped by the optical system in order to maximize their power concentration in the volume of the laser medium. Femtosecond pulses were generated in the self-synchronization regime of longitudinal modes by using a semiconductor saturable absorber. The mean power of the oscillator reached 150mW at λ≈1030nm when the pulse width was about 200fs. The product of the pulse width by the width of the emission spectrum was only a factor of 1.17 greater than the theoretical limit for the pulse shape described by the sech2 function. The master oscillator thus developed can be used as a self-contained source of femtosecond light pulses and as an initiating source for femtosecond laser amplifier systems.