Reconfigurable Resonant Multimode Nonlinear Coupling for UV-to-infrared Frequency Generation

TL;DR

This paper demonstrates a reconfigurable on-chip system that combines $ ext{chi}^{(2)}$ and $ ext{chi}^{(3)}$ nonlinearities in a silicon nitride microresonator to generate coherent light from ultraviolet to near-infrared wavelengths, enabling tunable and versatile frequency conversion.

Contribution

It introduces a novel reconfigurable multimode nonlinear coupling approach that enables broad and tunable UV-to-NIR light generation in a single microresonator using all-optical poling.

Findings

Achieved coherent UV-to-NIR light generation in a silicon nitride microresonator.

Demonstrated reconfigurable second harmonic generation and optical parametric oscillation.

Enabled highly tunable NIR light through hybrid modal phase matching.

Abstract

On-chip coherent visible and near-infrared (NIR) light generation has broad applications in metrology, bio-sensing, and quantum information. High-Q microresonators are ideal candidates for generating light across such broad wavelength ranges via efficient second- ($\chi^{(2)}$) and third-order ($\chi^{(3)}$) nonlinear optical processes. However, harnessing these diverse nonlinearities simultaneously in a single microresonator remains elusive yet highly attractive both fundamentally and technologically. Here, we demonstrate coherent light generation from the ultraviolet to NIR in a silicon nitride microresonator pumped by a single continuous-wave telecom laser. This broad frequency generation arises from the interplay of $\chi^{(2)}$ and $\chi^{(3)}$ nonlinear processes. A cascade of nonlinear processes, including harmonic generation and optical parametric oscillation (OPO), is initiated by the photoinduced second harmonic generation enabled by all-optical poling. The dynamic reconfigurability of this $\chi^{(2)}$ nonlinearity enables access to different transverse spatial modes at the second harmonic, enabling highly tunable OPO processes triggered by hybrid modal phase matching conditions and yielding milliwatt-level NIR light. This work sheds new insights into the fundamental physics of cooperative nonlinear multimode interactions in resonant systems and provides a versatile approach for reconfigurable OPOs, highlighting their potential to generate light at wavelengths beyond the reach of photonic integrated lasers.