Observation of Optical Hysteresis in an all optical passive ring cavity

Abstract

We report the first observation of dispersive optical hysteresis in an all optical passive uni-directional ring cavity system. Ammonia gas is used as the non-linear medium for which a number of vibrational-rotational transitions (1) are in near coincidence with the step tunable emission from a TEA CO2 laser. Pronounced instabilities and optical hysteresis are found to occur over a gas pressure range commensurate with that for self-focussing A grating tunable hybrid TEA CO2 laser with amplifier, operating on a single mode, with a gain switched pulse duration of ~ 100 nsec was used. The laser output, sampled via a beam splitter, was coupled through a Ge flat (R = 36%) which formed one element of the three element ring cavity (cavity length ~ 3.5 m) comprising two plane mirrors and incorporating a 1 m long gas cell and beam splitter for sampling the cavity signal. Signals were recorded using photon drag detectors in conjunction with Tektronix 7904/7104 oscilloscopes.