Ultrabroadband midinfrared generation by using group-velocity-dispersion tailoring in a Bragg reflection waveguide for a difference-frequency-generation process

Abstract

We propose a novel scheme for ultrabroadband midinfrared (mid-IR) generation using quasi-phase-matched difference-frequency generation (DFG) in a GaN/Al(x)Ga(1-x)N based Bragg reflection waveguide (BRW). By optimally tailoring the phase- and group-velocity dispersion properties of symmetric BRWs, we show that the phase-matching condition for a DFG process could be maintained over a broad range of signal wavelengths. This could lead to generation of an approximately 700 nm broad idler close to 3.26 microm wavelength. Since the idea is based on dispersion compensation using photonic bandgap geometry, we can shift the broadband features to any desired spectral region and for any material system within the constraints imposed by the transparency of nonlinear materials. We also investigate the possibility of broadband mid-IR generation using pump sources with broad spectral width.