Second-harmonic generation using 4-bar-quasi-phasematching in a GaAs whispering-gallery-mode microcavity
Paulina S. Kuo, Glenn S. Solomon
The 4-bar crystal symmetry in materials such as GaAs can enable quasi-phasematching for efficient optical frequency conversion without poling, twinning or other engineered domain inversions. 4-bar symmetry means that a 90 degree rotation is equivalent to a crystallographic inversion. Therefore, when light circulates about the 4-bar axis, as in GaAs whispering-gallery-mode microdisks, it encounters effective domain inversions that can produce quasi-phasematching. Microdisk resonators also offer resonant field enhancement, resulting in highly efficient frequency conversion in micrometre-scale volumes. These devices can be integrated in photonic circuits as compact frequency convertors, sources of radiation or entangled photons. Here we present the first experimental observation of second-harmonic generation in a whispering-gallery-mode microcavity utilizing 4-bar-quasi-phasematching. We use a tapered fibre to couple into the 5-μm diameter microdisk resonator, resulting in a normalized conversion efficiency η ≈ 5 × 10^−5 mW^−1. Simulations indicate that when accounting for fibre-cavity scattering, the normalized conversion efficiency is η ≈ 3 × 10^−3 mW^−1.
and Solomon, G.
Second-harmonic generation using 4-bar-quasi-phasematching in a GaAs whispering-gallery-mode microcavity, Nature Communications, [online], https://doi.org/10.1038/ncomms4109
(Accessed December 1, 2023)