The Influence of Velocity-Changing Collisions on Resonant Degenerate Four-Wave Mixing

The phase conjugate signal observed in resonant degenerate fourwave mixing on the 63P2 to 73s1, transition of atomic mercury in a Hg-Ar discharge is investigated. At a fixed argon pressure the variation of the signal with pump powers is explained by a model that includes the effects of velocity-changing collisions (VCC‘s). As the argon pressure was varied from 0 to 1 torr an increase in the phase conjugate signal was observed and is ascribed to a change in the discharge dynamics with argon pressure and to the influence of VCC's. To further clarify the role of collisions and optical pumping, degenerate fourwave mixing spectra are examined as a function of pump power: Line shapes are briefly discussed. © 1989 IEEE