Effect of Waveguide Inhomogeneity in a χ(2)-Based Pulsed Optical Parametric Amplifier

Abstract

The effect of waveguide inhomogeneity in transmitted pulses of a χ(2)-based optical parametric amplifier is investigated. Periodically poled lithium niobate (PPLN) channel waveguides are used to achieve optical parametric amplification (OPA) via cascaded second harmonic generation and difference frequency generation (cSHG/DFG) process at telecommunication bandwidth. To access high input power, a Q-switched laser of low duty cycle was used for the fundamental source. The ns-pulsed fundamental generates the pump for the DFG (OPA) process via SHG. The signal amplification and the wavelength converted idler generation are achieved via DFG process between the SH and the signal. It is shown that inhomogeneity of the waveguide leads to change in the relative phase between interacting waves along the waveguide. Consequently, transmitted pulses are disturbed for an inhomogeneous waveguide. Experimental and theoretical results of transmitted pulses from a homogeneous and an inhomogeneous PPLN channel waveguides are presented. In the homogeneous channel guide with Gaussian-shaped transmitted pulses, more than 20 dB of parametric gain was achieved in an 88-mm-long waveguide when ∼1.7 W of coupled fundamental peak power is launched to the waveguide.