Comparison of phase quadrature squeezed states generated from degenerate optical parametric amplifiers using PPKTP and PPLN

Phase quadrature squeezed states at 1550 nm generated from degenerate optical parametric amplifiers (DOPAs) using periodically poled KTiOPO4 (PPKTP) and periodically poled lithium niobate (PPLN) are compared. A squeezing of 6.8 dB was produced from the DOPA using PPKTP with the phase matching temperature of 34.5 °C. By contrast, a measured squeezing of 4.9 dB was generated using PPLN with the phase matching temperature of 135.2 °C. The degradation of squeezing using a nonlinear crystal with a high phase matching temperature is explained by a theoretical model of DOPAs including the extra phase noise caused by the guided acoustic wave Brillouin scattering within the nonlinear crystal.