Continuous-wave Cascaded-Harmonic Generation and Multi-Photon Raman Lasing in Lithium Niobate Whispering-Gallery Resonators

TL;DR

This paper demonstrates continuous-wave cascaded-harmonic generation and Raman lasing in lithium niobate whispering-gallery resonators, achieving multiple harmonic and Raman processes at low pump power levels through enhanced intensity and quasi phase-matching.

Contribution

It presents the first experimental realization of simultaneous cascaded-harmonic and Raman lasing in a lithium niobate whispering-gallery resonator with low power requirements.

Findings

Achieved up to fourth-harmonic generation.

Observed stimulated Raman scattering at specific vibrational wavenumbers.

Demonstrated simultaneous harmonic and Raman lasing visually and spectrally.

Abstract

We report experimental demonstration of continuous-wave cascaded-harmonic generation and Raman lasing in a millimeter-scale lithium niobate whispering-gallery resonator pumped at a telecommunication-compatible infrared wavelength. Intensity enhancement through multiple recirculations in the whispering-gallery resonator and quasi phase-matching through a nonuniform crystal poling enable simultaneous cascaded-harmonic generation up to the fourth-harmonic accompanied by stimulated Raman, two-photon, three-photon, and four-photon Raman scattering corresponding the molecular vibrational wavenumbers 632 cm-1 and 255 cm-1 in z-cut lithium niobate at pump power levels as low as 200mW. We demonstrate simultaneous cascaded-harmonic generation and Raman lasing by observing the spectrum of the scattered light from the resonator and by capturing the image of the decoupled light from the resonator on a color CCD camera.