Zheng Yuanlin, Fang Zhiwei, Liu Shijie, Cheng Ya, Chen Xianfeng
State Key Laboratory of Advanced Optical Communication Systems and Networks, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.
Key Laboratory for Laser Plasma (Ministry of Education), Collaborative Innovation Center of IFSA, Shanghai Jiao Tong University, Shanghai 200240, China.
Phys Rev Lett. 2019 Jun 28;122(25):253902. doi: 10.1103/PhysRevLett.122.253902.
Exterior whispering-gallery modes (WGMs), whose mode energy is mainly confined outside the microcavity, can achieve large mode overlapping with the ambient environment, as well as a strong electric field and gradient force at the surface. Here, we demonstrate highly localized WGMs in the nanoair gap of a double-layer crystalline microdisk. The geometry is based on a horizontal slot-waveguide structure of two vertically stacked crystalline microdisks made of lithium niobate thin films. The slot WGM possesses a high quality factor in excess of 10^{5} without metallic loss. The absorption and scattering loss is reduced by use of the crystalline nanofilm at sub-nm rms surface roughness. The demonstrated configuration can be highly favored in various applications including optical sensing, nonlinear optics, and optomechanics.
外部回音壁模式（WGMs），其模式能量主要限制在微腔外部，可以实现与周围环境的大模式重叠，以及在表面产生强电场和梯度力。在此，我们展示了双层晶体微盘中纳米气隙中的高度局域化WGMs。该结构基于由铌酸锂薄膜制成的两个垂直堆叠的晶体微盘的水平狭缝波导结构。狭缝WGM具有超过10^5的高品质因数且无金属损耗。通过使用均方根表面粗糙度小于纳米的晶体纳米膜，吸收和散射损耗得以降低。所展示的结构在包括光学传感、非线性光学和光机械学在内的各种应用中非常有利。
