  High-gain optical parametric amplification is an important nonlinear process
used both as a source of coherent infrared light and as a source of
nonclassical light. In this work, we experimentally demonstrate an approach to
optical parametric amplification that enables extremely large parametric gains
with low energy requirements. In conventional nonlinear media driven by
femtosecond pulses, multiple dispersion orders limit the effective interaction
length available for parametric amplification. Here, we use the dispersion
engineering available in periodically poled thin-film lithium niobate
nanowaveguides to eliminate several dispersion orders at once. The result is a
quasi-static process; the large peak intensity associated with a short pump
pulse can provide gain to signal photons without undergoing pulse distortion or
temporal walk-off. We characterize the parametric gain available in these
waveguides using optical parametric generation, where vacuum fluctuations are
amplified to macroscopic intensities. When driven with pulse energies in excess
of 10 pJ, we observe saturated parametric gains as large as 88 dB (146 dB/cm).
The devices shown here achieve saturated optical parametric generation with
orders of magnitude less pulse energy than previous techniques.
