Nonlinear Optics at Ultralow Power using Metastable Xenon in a High Finesse Cavity

Abstract

Single-photon cross phase shifts and other single-photon nonlinearities have numerous applications in all-optical quantum information processing. Generating these nonlinearities though can be difficult. This has been done previously using sophisticated experiment setups, for instance using cold atoms optically trapped within the field mode of a high-finesse cavity. Several groups have experimentally achieved single-photon phase shifts on the order of ? using these systems. However, nonlinearities weaker than this have important applications as well. In this work we introduce and demonstrate the idea of using metastable xenon gas in a high-finesse cavity to produce weak single-photon nonlinearities. Our system is relatively simple and robust, avoids problems associated with the accumulation of alkali atoms on mirror surfaces, and is capable of approaching the strong coupling regime of cavity quantum electrodynamics. It can compete with the performance of state-of-the-art cavity systems up to a single-atom cooperativity of roughly ? ? 1. Beyond this, the effects of atomic motion begin to play a larger role and improving the system performance becomes more difficult. After a brief introduction to the use of optical cavities and the spectroscopic properties of metastable xenon, we demonstrate the feasibility of our approach by reviewing two proof-of-principle demonstrations performed in our lab. In these experiments, we measured absorption saturation and cross-phase modulation using a cavity of moderately high finesse F = 3,000. We found that nonlinear effects occurred at ultralow input power levels, proving that the presence of the cavity strongly enhanced the inherent optical nonlinearity of metastable xenon. We close by reviewing our recent progress in building an improved cavity system, which is expected to produce enhanced single photon cross phase shifts.