Rajagopal Sreekul Raj, Rosenberger A T
Department of Physics, Oklahoma State University, Stillwater, OK 74078, USA.
Sensors (Basel). 2022 Sep 1;22(17):6613. doi: 10.3390/s22176613.
Optical whispering-gallery microresonators have proven to be especially useful as chemical sensors. Most applications involve dispersive sensing, such as the frequency shift of resonator modes in response to a change in the ambient index of refraction. However, the response to dissipative interaction can be even more sensitive than the dispersive response. Dissipative sensing is most often conducted via a change in the mode linewidth owing to absorption in the analyte, but the change in the throughput dip depth of a mode can provide better sensitivity. Dispersive sensing can be enhanced when the input to the microresonator consists of multiple fiber or waveguide modes. Here, we show that multimode input can enhance dip-depth dissipative sensing by an even greater factor. We demonstrate that the multimode-input response relative to single-mode-input response using the same fiber or waveguide can be enhanced by a factor of more than one thousand, independent of the mode linewidth, or quality factor (), of the mode. We also show that multimode input makes the dip-depth response nearly one hundred times more sensitive than the linewidth-change response. These enhancement factors are predicted by making only two measurements of dip depth in the absence of an analyte: one with the two input modes in phase with each other, and one with them out of phase.
光学回音壁微谐振器已被证明作为化学传感器特别有用。大多数应用涉及色散传感，例如谐振器模式的频率偏移以响应环境折射率的变化。然而，对耗散相互作用的响应可能比色散响应更敏感。耗散传感最常通过由于分析物中的吸收导致的模式线宽变化来进行，但模式的通量凹陷深度的变化可以提供更好的灵敏度。当微谐振器的输入由多个光纤或波导模式组成时，色散传感可以得到增强。在这里，我们表明多模输入可以以更大的系数增强凹陷深度耗散传感。我们证明，使用相同的光纤或波导，相对于单模输入响应，多模输入响应可以增强一千多倍，与模式的线宽或品质因数（）无关。我们还表明，多模输入使凹陷深度响应比线宽变化响应敏感近一百倍。这些增强系数仅通过在没有分析物的情况下对凹陷深度进行两次测量来预测：一次是两个输入模式彼此同相，另一次是它们异相。
