Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, USA.
Sci Rep. 2013;3:1436. doi: 10.1038/srep01436.
Photonic nanocavities are a key component in many applications because of their capability of trapping and storing photons and enhancing interactions of light with various functional materials and structures. The maximal number of photons that can be stored in silicon photonic cavities is limited by the free-carrier and thermo-optic effects at room temperature. To reduce such effects, we performed the first experimental study of optical nonlinearities in ultrahigh-Q silicon disk nanocavities at cryogenic temperatures in a superfluid helium environment. At elevated input power, the cavity transmission spectra exhibit distinct blue-shifted bistability behavior when temperature crosses the liquid helium lambda point. At even lower temperatures, the spectra restore to symmetric Lorentzian shapes. Under this condition, we obtain a large intracavity photon number of about 40,000, which is limited ultimately by the local helium phase transition. These new discoveries are explained by theoretical calculations and numerical simulations.
光子纳米腔因其能够捕获和存储光子以及增强光与各种功能材料和结构的相互作用，是许多应用中的关键组件。在室温下，硅光子腔中可以存储的最大光子数受到自由载流子和热光效应的限制。为了减少这些影响，我们在超流氦环境中对超高质量因子硅盘纳米腔中的光非线性进行了首次低温实验研究。在升高的输入功率下，当温度越过液氦 λ 点时，腔传输光谱表现出明显的蓝移双稳行为。在更低的温度下，光谱恢复为对称的洛伦兹形状。在这种情况下，我们获得了大约 40000 的大腔内光子数，这最终受到局部氦相变的限制。这些新发现通过理论计算和数值模拟得到了解释。
