Relative intensity squeezing by four-wave mixing with loss: An analytic model and experimental diagnostic

Four-wave mixing near resonance in an atomic vapor can pro- duce relative intensity squeezed light suitable for precision measurements beyond the shot-noise limit. We develop an analytic distributed gain/loss model to describe the competition of mixing and absorption through the non-linear medium. Using a novel matrix calculus, we present closed-form expressions for the degree of relative intensity squeezing produced by this system.We use these theoretical results to analyze experimentally measured squeezing from a 85Rb vapor and demonstrate the analytic modela??s utility as an experimental diagnostic.