Latest advances in optical frequency combs based on quadratic non-linearity

Abstract

Second-order non-linear susceptibility (χ2) is the cause of many non-linear processes in optics including second harmonic generation, sum frequency generation and difference frequency generation. Optical frequency combs based on χ2, i.e. quadratic frequency combs, hold the promise of reducing the devices power consumption and footprint since χ2 materials present a stronger non-linearity than χ3 materials, which suggests that higher efficiencies can be achieved. In this work, we will revisit the latest quadratic combs experimental advances, concerning power threshold, span and wavelength conversion efficiency.