Efficient telecom-to-visible spectral translation through ultralow power nonlinear nanophotonics

The ability to spectrally translate lightwave signals in a compact, low-power platform is at the heart of the promise of nonlinear nanophotonic technologies. For example, a device to connect the telecommunications band with visible and short near-infrared wavelengths can enable a connection between high-performance chip-integrated lasers based on scalable nanofabrication technology with atomic systems used for time and frequency metrology. Although second-order nonlinear (chi((2))) systems are the natural approach for bridging such large spectral gaps, here we show that third-order nonlinear (chi((3))) systems, despite their typically much weaker nonlinear response, can realize spectral translation with unprecedented performance. By combining resonant enhancement with nanophotonic mode engineering in a silicon nitride microring resonator, we demonstrate efficient spectral translation of a continuous-wave signal from the telecom band (similar to 1,550 nm) to the visible band (similar to 650 nm) through cavity-enhanced four-wave mixing. We achieve such translation over a wide spectral range >250 THz with a translation efficiency of (30.1 +/- 2.8)% and using an ultralow pump power of (329 +/- 13) mu W. The translation efficiency projects to (274 +/- 28)% at 1 mW and is more than an order of magnitude larger than what has been achieved in current nanophotonic devices.