具有内参考热补偿功能的三层膜结构微球腔折射率传感器

Triple-layer-coated microspheres for refractive index sensor with internally referenced self-compensated thermal effect

tBtB光学微腔在高灵敏度传感中有着重要的应用前景,而在传感中热漂移是制约其走向实用的重要因素.本文提出了一种镀有三层膜结构的微球腔,可以在实现高灵敏度折射率传感的同时,具备内参考热补偿功能.该结构由内到外分别涂覆折射率为高、低、高的薄膜,内外两高折射率层可以分别支持各自的回音壁模式,称之为内层模式和外层模式.研究了波导耦合的内外模式在折射率传感和温度传感应用的表现.结果表明,中间膜层厚度为550 nm时,内外模式的折射率灵敏度分别为0.0168和102.56 nm/RIU,温度灵敏度分别为–19.57和–28.98 pm/K.通过监测内外模式谐振波长的差值进行传感,对中间膜层厚度进行优化,=400 nm时,折射率灵敏度为75.219 nm/RIU,探测极限可以达到2.2×10^–4 RIU,热漂移被减小到3.17 pm/K,极大地减小了热漂移对系统的影响.本研究可为微球腔折射率传感器的设计和改进提供指导.

Optical microcavity has an important and promising application in high sensitivity sensing,but thermal drift hinders its practical use.In this study,we propose a triple-layer-coated microsphere resonator,which has a high sensitivity in refractive index sensing with low thermal drift.The refractive indexes of the three layers from the inside to the outside are high,low,and high,respectively.The two high refractive index layers can support their own whispering-gallery modes,called the inner mode(IM)and the outer mode(OM).We study the performance of IM and OM with waveguide coupling in refractive index sensing and temperature sensing.The results show that when the thickness of the middle layer is 550 nm,the refractive index sensitivity of IM and OM will be 0.0168 nm/RIU,102.56 nm/RIU,and the temperature sensitivity will be–19.57 pm/K and–28.98 pm/K,respectively.The sensing is carried out by monitoring the difference in resonant wavelength between IM and OM and the sensing characteristics are optimized by adjusting the thickness of the middle layer.Further,when tB=400 nm,the refractive index sensitivity can arrive at 75.219 nm/RIU,the detection limit can reach 2.2×10^–4 RIU,and the thermal drift is reduced to 3.17 pm/K,thereby eliminating the effect of thermal drift to a great degree.This study provides the guidance for designing and improving the microsphere refractive index sensors.