Amplitude squeezing of light by means of a phase-sensitive fiber parametric amplifier

Bright sub-Poissonian light generation was realized from a balanced nonlinear Sagnac interferometer. The approach utilized employs two orthogonally polarized pulses to cancel the noise due to guided-acoustic-wave Brillouin scattering, which is predominantly of the same polarization as the input signal. In addition, nonlinear and phase-sensitive amplification is achieved by injecting a coherent-state input signal, which can be either amplified or deamplified depending on its phase relative to that of the pump. Sub-Poissonian output is realized in the case of deamplification even when the signal power is comparable in magnitude with that of the pump, making the quantum noise reduction robust with respect to the pump leakage into the signal arm.