title: Second-harmonic generation using 4-quasi-phasematching in a GaAs whispering-gallery-mode microcavity.
abstract: The 4 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 symmetry means that a 90° rotation is equivalent to a crystallographic inversion. Therefore, when light circulates about the 4 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 -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).
authors.affiliation: Joint Quantum Institute, National Institute of Standards and Technology, & University of Maryland, Gaithersburg, Maryland 20899, USA.
authors.forename: Paulina S
authors.initials: PS
authors.lastname: Kuo
authors.affiliation: 1] Joint Quantum Institute, National Institute of Standards and Technology, & University of Maryland, Gaithersburg, Maryland 20899, USA [2] Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de Madrid, 28049 Madrid, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Bravo-Abad
authors.affiliation: Joint Quantum Institute, National Institute of Standards and Technology, & University of Maryland, Gaithersburg, Maryland 20899, USA.
authors.forename: Glenn S
authors.initials: GS
authors.lastname: Solomon