Optimization of gain in traveling-wave optical parametric amplifiers by tuning the offset between pump- and signal-waist locations.

We present experimental demonstration and modeling of the optimization of a phase-sensitive optical parametric amplifier by tuning the relative position between the pump and signal beam waists along the propagation direction. At the optimum position, the pump beam focuses after the signal beam, and this departure from colocated waists increases with increasing pump power. Such optimization leads to more than 3 dB improvement in the measured deamplification response of the amplifier.