Experimental and theoretical study of a femtosecond laser

It is demonstrated experimentally and theoretically that a cw dye laser with a ring cavity resonator and a passive mode locking can emit pulses of variable duration ranging from 1 psec down to 55 fsec and wavelengths from 615 to 624 nm. The tuning of the pulse duration is achieved by varying the optical path in an intracavity glass prism. Phase modulation because of saturation of a nonlinear absorber compresses the pulses in the dispersive material of the prism. A theoretical model of mode self-locking between colliding pulses is proposed.