Pulse shortening to 25 ps in a cw mode-locked Nd: YAG laser by introducing an intracavity etalon

The gain spectrumG(v) of a cw mode-locked Nd:YAG laser is flattened by a properly designed intracavity etalon. The increase in amplification bandwidth allows the generation of very stable trains of pulses shorter than that of standard systems. A reduction of the pulse width from 70 to 25 ps is observed by incorporating a BK 7 platelet of 420 m thickness in the resonator. The properties of the laser are investigated as a function of the thickness and the orientation angle of the etalon. The laser performance is found to be considerably influenced by the fact that the Nd³⁺ laser transition at 1.064 m consists of a line doublet.