Pulse compression inside an actively AM mode-locked Nd:YAG laser using a liquid Kerr cell

A mode-locked Nd:YAG laser capable of generating pulses substantially shorter than the present limit of 30-50 ps, while retaining the stability of active mode locking, would be a useful development. This study presents a simplified theoretical analysis and a preliminary experimental verification of the use of an optical Kerr cell as a passive lossless pulse compressor inside a Q-switched and actively mode-locked YAG laser. The theoretical model indicates possible compression to as short as about 5 ps in a typical low-power Nd:YAG laser. The preliminary experimental results show substantial pulse compression via the predicted mechanism, though still not below about 30 ps. The technique appears capable, however, of pulse compression to substantially shorter values without the instabilities, statistical fluctuations, or energy losses associated with saturable-absorber mode locking.