Cascaded optical parametric generation in reverse-proton-exchange lithium niobate waveguides

Cascaded optical parametric generation in lithium niobate waveguides involves simultaneous quasi-phase- matching of optical parametric generation and sum-frequency generation. We study details of this process in reverse-proton-exchange lithium niobate waveguides with quasi-phase-matching gratings from 6 to 42 mm in length. We identify the cascaded products in the time domain using a frequency-resolved cross correlator and study cascaded optical parametric generation under different levels of pump depletion. With phase-modulated gratings, we demonstrate control over the wavelength of the near-transform-limited signal pulses from cascaded optical parametric generation. With its low threshold and controllable temporal properties, cascaded optical parametric generation in reverse-proton-exchange waveguides can be a promising candidate for a tunable light source.