Raman-noise induced quantum limits for χ nondegenerate phase-sensitive amplification and quadrature squeezing

We present a quantum theory of nondegenerate phase-sensitive parametric amplification in a χ nonlinear medium. The non-zero response time of the Kerr (χ) nonlinearity determines the quantum-limited noise figure of χ parametric amplification, as well as the limit on quadrature squeezing. This non-zero response time of the nonlinearity requires coupling of the parametric process to a molecular-vibration phonon bath, causing the addition of excess noise through spontaneous Raman scattering. We present analytical expressions for the quantum-limited noise figure of frequency non-degenerate and frequency degenerate χ parametric amplifiers operated as phase-sensitive amplifiers. We also present results for frequency non-degenerate quadrature squeezing. We show that our non-degenerate squeezing theory agrees with the degenerate squeezing theory of Boivin and Shapiro as degeneracy is approached. We have also included the effect of linear loss on the phase-sensitive process. c © 2008 Optical Society of America