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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.
Nature Communications


nonlinear frequency conversion, Second-harmonic generation, gallium arsenide, microdisk resonator, quasi-phasematching, 4-bar symmetry


Kuo, P. and Solomon, G. (2014), Second-harmonic generation using 4-bar-quasi-phasematching in a GaAs whispering-gallery-mode microcavity, Nature Communications, [online], (Accessed May 26, 2024)


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Created January 17, 2014, Updated November 10, 2018