Fig. 1: Nonlinear cascaded parametric down-conversion processes.
From: Cascaded nonlinear down-conversion in poling-free lithium niobate nanophotonic waveguides
a Schematic diagram of MIR light generation through the cascaded OPG-DFG process in a reverse-polarization dual-layer nanophotonic TFLN waveguide. b Energy level diagram. Left: OPG processes. Right: DFG processes. c Schematic diagram depicting the spectrum produced by the cascaded process. d Mode profiles of various frequency components in the cascaded process. The upper images depict the modes of the pump light and the newly generated pump light. The lower images illustrate the modes of the signal light generated through degenerate OPG and the MIR produced via the cascaded OPG-DFG process. e SEM image of the waveguide cross-section (Scale bar: 1 μm). The upper left inset: top view of the waveguide (Scale bar: 5 μm); Bottom inset: the waveguide height.
