Ultrahigh-efficiency second-harmonic generation in nanophotonic PPLN waveguides

TL;DR

This paper demonstrates ultrahigh-efficiency second-harmonic generation in nanostructured PPLN waveguides, achieving over 20 times higher efficiency than traditional waveguides, enabling advanced chip-scale photonic integration.

Contribution

The authors develop nanostructured PPLN waveguides with record-high normalized efficiency for second-harmonic generation using sub-wavelength confinement and precise periodic poling.

Findings

Normalized efficiency of 2600%/W-cm² achieved

Efficiency exceeds state-of-the-art by over 20 times

Potential for chip-scale classical and quantum photonics

Abstract

Periodically poled lithium niobate (PPLN) waveguide is a powerful platform for efficient wavelength conversion. Conventional PPLN converters however typically require long device lengths and high pump powers due to the limited nonlinear interaction strength. Here we use a nanostructured PPLN waveguides to demonstrate an ultrahigh normalized efficiency of 2600%/W-cm$^2$ for second-harmonic generation of 1.5-$\mu$m radiation, more than 20 times higher than that in state-of-the-art diffused waveguides. This is achieved by a combination of sub-wavelength optical confinement and high-fidelity periodic poling at a first-order poling period of 4 $\mu$m. Our highly integrated PPLN waveguides are promising for future chip-scale integration of classical and quantum photonic systems.