ROLE OF A SUPERCONTINUUM IN THE GENERATION OF ROTATIONAL RAMAN EMISSION BASED ON STIMULATED RAMAN GAIN AND 4-WAVE RAMAN MIXING

Rotational Stokes emission is generated by focusing a linearly-polariz ed femtosecond pump beam into molecular hydrogen with a supercontinuum , which occurs by self phase modulation as a result of passing the bea m through molecular nitrogen. The supercontinuum acts as a seed beam i n the generation of rotational Stokes emission, However, enhancement o f the supercontinuum by increasing the peak power suppresses the gener ation of the rotational Raman emission, due to a large gain fur the su per-continuum and to the poor beam focusing capability of the pump bea m, probably as a result of self focusing. (C) 1998 Elsevier Science B. V.