提出一种基于集成光波导沟槽耦合器的超紧凑折射率传感器。该结构包括入射波导、反射波导及透射波导,亚微米宽的沟槽位于入射波导与反射波导的交汇处。入射波导中的导波光在沟槽侧壁发生受抑全内反射,使得一部分光经消逝场耦合进入透射波导,另一部分光被反射进入反射波导。透射光强度取决于消逝场耦合效率,而后者依赖于沟槽填充物的折射率,这意味着这种集成光波导沟槽耦合结构可作为微纳传感器用于实时探测液体折射率或溶液浓度。以氮化铝脊型波导为例,对这种新型折射率传感器进行仿真设计和仿真验证,经过结构优化,其折射率灵敏度可达207.05 %/RIU。

An ultracompact refractive index sensor based on an integrated optical waveguide trench coupler is proposed herein. The structure includes incident, reflection, and transmission waveguides as well as a submicron-wide trench which is located at the intersection of the incident and the reflection waveguides. The guided wave in the incident waveguide occurs, and the frustrated total internal reflection at the sidewall of the trench makes it so that the light can be partly converted into a transmission wave through evanescent field coupling, while the other partial light will be reflected into the reflection waveguide. The intensity of the transmission light depends on the coupling efficiency of evanescent field, and the reflection light intensity depends on the refractive index of the trench, implying that this integrated optical waveguide trench coupler can be used as a micro/nanosensor for the real-time detection of liquid refractive index or solution concentration. Herein, the new refractive index sensor based on the aluminum nitride rib waveguide is designed and verified via simulation. After the structural optimization, the refractive index sensor has a sensitivity of 207.05%/RIU.