用室温主动拉曼增益介质实现增益,相移和群速度的相位控制

Abstract

A four-level tripod active-Raman-gain scheme is analyzed for obtaining phase-controlled gain, phase shift, and group velocity at room temperature. The scheme can be used to eliminate significant probe field attenuation or distortion which is unavoidable in the scheme based on electromagnetically induced transparency. It is shown that the intensity gain, phase shift, and group velocity of a probe field can be simultaneously manipulated by changing the relative phase of two pump fields. The scheme is also different from that proposed recently by Deng et al. where a probe-field gain always exists. New features of the scheme presented here raise the possibility of designing rapidly responding optical switches and gates for optical information processing. OCIS codes: 020.1670, 270.1670. doi: 10.3788/COL20090707.0549. Control of intensity, phase, and propagating velocity of electromagnetic fields has great technological importance in the field of information science. In a solid state medium such as an optical fiber [1] , the requirement of low light absorption necessarily implies the system must work in off-resonance regime, which means that an active control is difficult due to the lack of distinctive energy levels and transition selection rules. In recent years, much effort has been made to study the optical property of active media via electromagnetically induced transparency (EIT) [2] , in which an on-resonance excitation scheme is employed. Due to the quantum interference effect induced by a control field, the light wave propagation in such media displays many striking features, including a large suppression of optical absorption, a significant reduction of group velocity, and a great enhancement of nonlinear Kerr effects, which are promising for many practical applications in optical information processing [3−6] .