Whispering-gallery microcavities have been used to realize a variety of efficient parametric nonlinear optical processes through the enhanced light–matter interaction brought about by supporting multiple high quality factor and small modal volume resonances. Critical to such studies is the ability to control the relative frequencies of the cavity modes, so that frequency matching is achieved to satisfy energy conservation. Typically this is done by tailoring the resonator cross section. Doing so modifies the frequencies of all of the cavity modes, that is, the global dispersion profile, which may be undesired, for example, in introducing competing nonlinear processes. Here, we demonstrate a frequency engineering tool, termed multiple selective mode splitting (MSMS), that is independent of the global dispersion and instead allows targeted and independent control of the frequencies of multiple cavity modes. In particular, we show controllable frequency shifts up to 0.8 nm, independent control of the splitting of up to five cavity modes with optical quality factors ≳105, and strongly suppressed frequency shifts for untargeted modes. The MSMS technique can be broadly applied to a wide variety of nonlinear optical processes across different material platforms and can be used to both selectively enhance processes of interest and suppress competing unwanted processes.

中文翻译：

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用于微腔非线性光学的通用频率工程工具：回音壁共振的多重选择性模式分裂


回音壁微腔已被用于通过支持多个高品质因数和小模态体积共振带来的增强的光-物质相互作用来实现各种有效的参量非线性光学过程。此类研究的关键是能够控制腔模的相对频率，从而实现频率匹配以满足能量守恒。通常，这是通过定制谐振器横截面来完成的。这样做会修改所有腔模式的频率，即全局色散分布，这可能是不期望的，例如，在引入竞争非线性过程时。在这里，我们演示了一种频率工程工具，称为多选择性模式分裂（MSMS），它独立于全局色散，而是允许对多个腔模式的频率进行有针对性的独立控制。特别是，我们展示了高达 0.8 nm 的可控频移、对多达 5 个腔模的分裂的独立控制（光学品质因数 ≳105）以及对非目标模式的强烈抑制频移。 MSMS 技术可广泛应用于不同材料平台上的各种非线性光学过程，并且可用于选择性增强感兴趣的过程并抑制竞争的不需要的过程。