A giant self-Kerr nonlinearity using phase-sensitive excitation in a closed three-level atomic system

A third-order nonlinear response is investigated theoretically using a closed lambda system. In this scheme, a pair of optical fields and a microwave field connect three hyperfine levels in a cyclic fashion, rendering the atomic response sensitive to the relative phase of all three fields. Changing the relative phase, we can suppress the linear response of the probe field and enhance its third order self-Kerr nonlinear response using the underlying electromagnetically induced transparency (EIT) effect. The resultant giant self-Kerr nonlinear response is comparable to or exceeding that found in atomic systems at room temperature. Most importantly, we show that the self-Kerr nonlinear response at an optical frequency can be controlled using the phase and amplitude of a frequency-separated microwave field.