Analysis of stable operation of ultrashort pulse distributed feedback dye laser oscillator

The output modes of sub-picosecond ultrashort pulse distributed feedback dye laser which is used as an oscillator for a high brightness KrF laser system were analyzed with coupling wave theory. The analysis shows that for a practical distributed feedback dye laser, single longitudinal mode oscillation is always obtained because of periodical gain modulation. A method based on spectrum modulation measurement to obtain a stable single pulse operation of DFDL was provided as well as numerical simulation．The measured spectrum shows that for the sub-picosecond DFDL used in the laser system, a stable single pulse, single longitudinal mode output is obtained under two times above pumping threshold．