Generation of tunable ultrashort pulses in a dynamic distributed feedback laser

A study was made of the operation of a dynamic distributed feedback (DFB) laser utilizing dyeactivated polyurethane and pumped by a train of ultrashort pulses from a YAG:Nd³⁺ laser. An interference system with division of the pump pulse duration was used to produce the dynamic DFB. Direct measurements were made of the duration of the generated pulses using an Agat-SF streak camera and it was found that the duration of the output pulses was considerably shorter (up to four times) than that of the pump pulses. Tuning in the 560-600 nm range with an ultrashort pulse duration of ~8 psec, a divergence of ~1 mrad, and a lasing efficiency of ~ 3 % were achieved. The evolution of the ultrashort pump and lasing pulse trains indicated that a thermal phase grating had no influence on the operation of this laser.