Bandwidth-enhanced quadratic soliton formation by on-sample single-band amplification

Abstract

Optical solitons mediated by cascading of quadratic nonlinearities constitute an active area of research. Interest is driven by the new phenomena that are uncovered and by their potential applications in light beam and pulse manipulation schemes, including cavity and laser systems containing quadratic nonlinear crystals. Quadratic solitons form by the mutual trapping between the multiple waves that parametrically interact through the crystal. When only one of the involved frequencies is input into the crystal, efficient soliton formation at moderate light intensities can only be achieved in a narrow-band of phase mismatches. The bandshape, bandwidth and achievable maximum depend on the set-up considered, and on the input light power. In this paper we show that both the efficiency and the bandwidth, of quadratic soliton excitation can be importantly enhanced by simultaneous frequency-doubling and linear amplification of the fundamental frequency input signal. Such a scheme is realized in self-frequency-doubling optical amplifiers. We focus on spatial solitons in frequency-doubling planar waveguides, but the analysis can be extended to bulk geometries and to temporal solitons.