Efficient parametric down-conversion by gain-trapped solitons

Abstract

Optical parametric amplification is one of the most flexible approaches for generating coherent light at long wavelengths, but typical implementations require prohibitively large pump pulse energies to realize useful amounts of gain. In this work, we experimentally demonstrate an approach to optical parametric amplification in which an interplay between parametric gain and symmetric temporal walk-off confines the non-degenerate signal and idler to form a three-wave soliton. Gain-trapped solitons propagate stably over arbitrarily long interaction lengths, which reduces the energy required for high-gain operation by orders of magnitude. The devices demonstrated here realize large parametric gains (>70dB) with only picojoules of pump pulse energy in a 5-mm-long thin-film lithium niobate on sapphire nanowaveguide. In addition, we observe an array of desirable features including high conversion efficiencies (>50%), wide tuning ranges (>100nm), and broad spectral bandwidths (>180nm 3 dB for the 3200-nm idler). When combined with the dispersion engineering available in tightly confining nanowaveguides, this approach enables high-gain optical parametric amplifiers operating at any wavelength.