OPTIMIZING HOMODYNE DETECTION OF QUADRATURE-NOISE SQUEEZING BY LOCAL-OSCILLATOR SELECTION

A general formalism is developed for optimizing homodyne detection of quadrature-noise squeezing by selection of the local-oscillator (LO) f ield. The optimum LO is the minimum-eigenvalue eigenfunction of a part icular Fredholm integral equation whose kernel depends on the signal f ield's normally ordered and phase-sensitive covariance functions. The squeezing that results from use of the optimum LO equals one plus twic e its associated eigenvalue. A continuous-wave (cw) simplification of the general formalism is presented for the case of stationary signal-f ield covariances when the homodyne photocurrent is spectrum analyzed. Another simplified special case is exhibited for single-spatial-mode o peration, such as is encountered in fiber-based quantum-noise experime nts. 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 func tion. The single-spatial-mode framework is employed to find the optimu m LO field and its squeezing performance for pulsed squeezed-state gen eration in a single-mode optical fiber whose Kerr nonlinearity has a n oninstantaneous 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-w ave mixing. (C) 1997 Optical Society of America.