Nonlinear Optical Systems Interacting with Amplitude-Modulated Optical Fields

摘要

This thesis is concerned with the interact ion of amplitude-modulated (AM)optical fields with various nonlinear systems. An experimental and theoretical analysis of three distinct nonlinear systems is treated: two-level atoms interacting with a 100% AM field: a four-level laser amplifier with an AM pump intensity: a multimode dye laser with an AM pump intensity. A 100% AM field is the limiting case of strong modulation in which the energy at the carrier frequency is completely suppressed, and only the modulation sidebands remain. The interaction of such an optical field with an ensemble of radiatively broadened two-level atoms (an optically-pumped sodium atomic beam is used) yields a complicated series of parametric resonances when both the Rabi frequency and the modulation frequency are large compared with the atomic-transition linewidth. The time-averaged fluorescence, and therefore, the absorption of energy exhibits parametric-resonant enhancement whenever the modulation frequency is equal to a subharmonic of the Rabi frequency. Population oscillations in a multilevel laser amplifier are studied using weak amplitude-modulation spectroscopy. Two laser fields are applied to a four level laser amplifier (alexandrite is used as the amplifier). (R.R.H.)