Abstract

Low-frequency (1 to 70 cm⁻¹) stimulated Stokes (i.e., red-shifted.) scattering of polarizable molecules such as carbon disulfide has been observed in liquid-filled hollow core fibers and microdroplets. Such geometries provide long interaction pathlengths for the buildup of nonlinear optical processes. The stimulated low-frequency emission was initially called stimulated Kerr scattering¹ and the scattering mechanism was attributed to molecular reorientation. Recent stimulated gain spectroscopy² results suggest that interaction-induced librational oscillation of molecules can give rise to substantial gain in the 0 to 100 cm⁻¹ region of the pump laser. Thus the low- frequency scattering has been called stimulated librational scattering (SLS) in microdroplets.³ Feedback occurs at discrete frequencies that correspond to the droplet cavity modes, commonly referred to as morphology dependent resonances (MDRs), to increase the effective interaction length. Stimulated Raman scattering (SRS) of various Raman modes of different liquids have been observed. The intense SRS generated can act as a very efficient pump, giving rise to multiple orders of SRS and SLS in the droplets.

© 1997 Optical Society of America