Kuo Paulina S, Bravo-Abad Jorge, Solomon Glenn S
Joint Quantum Institute, National Institute of Standards and Technology, & University of Maryland, Gaithersburg, Maryland 20899, USA.
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.
Nat Commun. 2014;5:3109. doi: 10.1038/ncomms4109.
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).
诸如砷化镓等材料中的四重晶体对称性能够实现准相位匹配，从而在无需极化、孪生或其他工程化畴反转的情况下实现高效的光频率转换。四重对称性意味着90°旋转等同于晶体学反演。因此，当光围绕四重轴传播时，如在砷化镓回音壁模式微盘中，它会遇到能产生准相位匹配的有效畴反转。微盘谐振器还能增强谐振场，从而在微米尺度的体积内实现高效的频率转换。这些器件可作为紧凑型频率转换器、辐射源或纠缠光子集成到光子电路中。在此，我们展示了利用四重准相位匹配在回音壁模式微腔中产生二次谐波的首次实验观测结果。我们使用一根锥形光纤耦合到直径为5μm的微盘谐振器中，得到归一化转换效率η≈5×10⁻⁵mW⁻¹。模拟表明，考虑到光纤 - 微腔散射时，归一化转换效率为η≈3×10⁻³mW⁻¹。
