Buildup of steady-state femtosecond pulses in a colliding-pulse mode-locked dye laser

Abstract

We have studied the evolution of the pulse widths and the corresponding spectra of femtosecond optical pulses generated by a colliding-pulse mode-locked (CPM) dye laser (λ = 620 nm) with (case I) and without (case II) compensating prisms. The build-up time to steady state took ~10 µs for case I. The peak wavelength of the corresponding spectra shifted slightly to the red as the pulses evolved. Otherwise, the spectra did not exhibit distinct features. In case II, the pulse width exhibited an oscillatory behavior and approached the steady state after a delay of ~50 µs. A dramatically changed spectrum was also observed at the first minimum of oscillation. These results were in good agreement with our proposed physical mechanisms.