A general formalism is developed for optimizing homodyne detection of quadrature-noise squeezing by selection of the local-oscillator (LO) field. The optimum LO is the minimum-eigenvalue eigenfunction of a particular Fredholm integral equation whose kernel depends on the signal field's normally ordered and phase-sensitive covariance functions. The squeezing that results from use of the optimum LO equals one plus twice its associated eigenvalue. A continuous-wave (cw) simplification of the general formalism is presented for the case of stationary signal-field covariances when the homodyne photocurrent is spectrum analyzed. Another simplified special case is exhibited for single-spatial-mode operation, such as is encountered in fiber-based quantum-noise experiments. The cw-source–spectrum-analysis approach is used to determine the optimum LO field and its squeezing performance for cw squeezed-state generation in a bulk Kerr medium with a Gaussian spatial-response function. The single-spatial-mode framework is employed to find the optimum LO field and its squeezing performance for pulsed squeezed-state generation in a single-mode optical fiber whose Kerr nonlinearity has a noninstantaneous response function. Comparison of the cw limit of this pulsed analysis with previous cw fiber-squeezing theory reveals a new regime for quadrature-noise reduction: Raman squeezing in fiber four-wave mixing.
© 1997 Optical Society of America
Jeffrey H. Shapiro and Asif Shakeel, "Optimizing homodyne detection of quadrature-noise squeezing by local-oscillator selection," J. Opt. Soc. Am. B 14, 232-249 (1997)