Whispering gallery mode resonator sensors are nondisruptive optical sensors that can detect and monitor perturbations in a gaseous environment. Through its resonant properties of peak wavelength, amplitude, and quality factor (Q factor), changes in concentration can be quantified within seconds and monitored over days with great stability. In addition, the small footprint, low cost, and high sensitivity are ideal properties for a disposable sensor that can be utilized in extreme environments. The large Q factor of the resonant cavity enables long interaction lengths and amplifies the effect of small changes in the background refractive index, which is detectable in picometer shifts of the resonance wavelength. However, this measurement is susceptible to changes in other environmental factors such as temperature, pressure, and humidity, which manifest on the picometer wavelength scale, reinforcing the need to decouple the variables. In this work, we compare the spectral response of different diameter resonators to carbon dioxide, nitrogen, and its mixtures, observing the spectral shifting and broadening of the cavity resonance near 1550 nm. In addition, the effect of environmental temperature on spectral shifting due to the thermo-optic effect is characterized and quantified. Lastly, the gas concentrations are changed in real time to showcase the tracking and recovery capabilities of the resonator sensor.

中文翻译：

---

使用光学微球谐振器传感器实时跟踪二氧化碳浓度

回音壁模式谐振器传感器是非破坏性光学传感器，可以检测和监测气体环境中的扰动。通过其峰值波长、振幅和品质因数（Q 因数）的谐振特性，可以在几秒钟内量化浓度变化，并在数天之内以极高的稳定性进行监测。此外，占地面积小、成本低和灵敏度高是可在极端环境中使用的一次性传感器的理想特性。谐振腔的大 Q 因子可实现较长的相互作用长度，并放大背景折射率微小变化的影响，这可以在谐振波长的皮米位移中检测到。然而，这种测量很容易受到其他环境因素（例如温度、压力和湿度）的变化的影响，这些变化在皮米波长范围内表现出来，从而加强了对变量进行解耦的需要。在这项工作中，我们比较了不同直径谐振器对二氧化碳、氮气及其混合物的光谱响应，观察了 1550 nm 附近腔谐振的光谱偏移和展宽。此外，还对环境温度对热光效应引起的光谱偏移的影响进行了表征和量化。最后，气体浓度实时变化，以展示谐振器传感器的跟踪和恢复能力。