Generation of midinfrared and visible radiation in a multiband phase-matched subwavelength LiNbO3 slab waveguide

An on-chip lithium niobate (LiNbO3) slab waveguide platform is proposed that simultaneously produces electric field pulses through sum and difference frequency generation. By controlling the geometry of the slab waveguide, phase-matching is achieved that produces radiation in the visible and midinfrared spectral bands. The slab waveguide confines the sum frequency generation wavelengths to the waveguide core and allows the difference frequency generation wavelengths to be emitted as Cherenkov waves. A finite-difference time-domain analysis is performed to study this multiband generation, where the LiNbO3 slab waveguide produces electric field pulses at a conversion efficiency of 14×10−5 and 0.5×10−5 through sum and difference frequency generation, respectively. This slab waveguide platform provides suitable design flexibility because the emission wavelengths are adjustable through proper choice of the waveguide core width and the excitation wavelengths. This source allows for better utilization of on-chip space by reducing the total number of devices necessary to achieve multiband light generation.