Self-Pulsing in an Optical Ring Cavity Coupled with Three-Level Atoms

Abstract

One of the reasons for the recent rising interest in electromagnetically induced transparency (EIT) in multilevel atomic systems [1] is its potential application in enhancing nonlinear optical processes. Several experiments were carried out recently to show that the atomic coherence effect in multi-level atomic systems could reduce absorption and enhance frequency conversion and four-wave mixing processes [2, 3]. On the other hand, when two level atoms are put into an optical cavity, many nonlinear processes, such as optical bistability and instability, occur. Recently, several theoretical papers proposed switching effects in three-level and four-level atomic systems with and without an optical cavity [4, 5]. These nonlinear optical effects are caused by enhanced Kerr-nonlinearity and dramatic changes in the dispersion slope due to atomic coherence in such multi-level atomic systems. Recently, we have measured the enhanced Kerr-nonlinear index of refraction n 2 of three-level A-type atoms by using an optical ring cavity and found a large modification of n 2 as functions of the frequency detunings of the probe and coupling lasers. We also observed self-pulsation of cavity transmission when the coupling frequency is tuned to atomic resonance and the probe frequency is detuned from resonance by a few MHz. In this paper, we report such observation and discuss its physical mechanism.