Pulse Train Instabilities and Pulse Structure Evolution in Nd:Yag Laser with Active Mode-Locking

The low-frequency instability (LFI) of the pulse-train envelope in actively mode locked (AML) laser strongly limits the range of parameters in which the pulse energy and pulse duration may be effectively controlled. It was shown experimentally [1-4] that the detuning of loss modulation frequency about few kHz in Nd:YAG lasers leads to appearance of LFI. Although numerous attempts were made for the theoretical investigation of AML destroying the origins of instabilities remain not clear yet. It was shown also [4,5] that for adequate determination of the width of stable locking region the single-pulse ( for example gaussian pulse [6]) approximation is not valid and it’s necessary to include the possibilities of the additive pulse formation within round-trip temporal interval.