Influence of thermal phase lattice on ultrashort pulses characteristics generated by DFDL

The lasers with distributed feed-back on dyes (DFDL) are interest of as perspective source of ultra short pulses of radiation (USI), which are generated under nanoseconds duration of pumping. In view of the luminescence quantum yield, distinct from unity and presence of Stokes losses, the part of a pumping pulse energy of the DFDL passes in heat and, thus, during operation of DFDL in the active medium thermal phase periodic lattice (TFL) is formed apart from periodic structure of inversion population. The presence of TFL in active medium influences on the process of generation development and results in changing of the generation characteristics of USI. The fulfilled numerical researches have shown that TFL has strong influence on the regime of USI generation and their generation characteristic at nanosecond duration of excitation pulses. The TFL influence consists in increasing of positive feedback and results in an elongation of USI in 1.5 times (under dye molecules concentration C-5/spl middot/10/sup -3/ moles/l). The decrease of concentration essentially magnifies the TFL contribution in the value of positive feedback. The power of single USI is augmented with growth of positive feedback and it is caused by increase of efficiency of a depletion of a upper laser level of molecules of the active medium. It is shown that the decreases of the TFL contribution in positive feedback can be achieved by means of reducing of threshold energy of pump.