Generation of tunable ultrashort light pulses by a laser with dynamic distributed feedback in an external ring resonator

Experimental and theoretical studies were made of the time and energy characteristics of a rhodamine 6G dye ring laser with optically induced distributed feedback, pumped synchronously by a train of ultrashort pulses from an actively mode-locked YAG:Nd laser with intracavity second harmonic generation. Narrow-band (~ 0.08 nm) generation of ~ 10 ps ultrashort pulses, tunable in the 568–602 nm range, and with a divergence of ~ 0.4 mrad was achieved. The energy efficiency was ~ 4% for each of the two output beams at a pump energy of 25 μJ. Under optimal conditions the duration of the output pulse was approximately twenty times shorter than that of the pump pulse. The results of the calculations using the proposed model show a good agreement with the experiments.