Ultrafast Self-Phase Modulation in a Colliding Pulse Mode-Locked Ring Dye Laser

In recent years, generation and application of ultrashort pulses from colliding pulse mode-locked (CPM) ring dye lasers 1-3) have attracted much attention for the study of ultrafast phenomena in the femtosecond region. We found that both spectral and temporal characteristics of these pulses are not simple but are largely affected by the self-phase modulation (SPM), strongly depending on the concentration of the absorber dye.