Kim Do-Hyun, Jeon Su-Jin, Lee Jae-Sang, Hong Seok-Ho, Choi Young-Wan
Department of Electrical and Electronics Engineering, Chung-Ang University, 221 Heuksuk-Dong, Dongjak-ku, Seoul 156-756, Korea.
Sensors (Basel). 2019 Aug 19;19(16):3600. doi: 10.3390/s19163600.
In this paper, a multi-mode waveguide-based optical resonator is proposed for an integrated optical refractive index sensor. Conventional optical resonators have been studied for single-mode waveguide-based resonators to enhance the performance, but mass production is limited owing to the high fabrication costs of nano-scale structures. To overcome this problem, we designed an S-bend resonator based on a micro-scale multi-mode waveguide. In general, multi-mode waveguides cannot be utilized as optical resonators, because of a performance degradation resulting from modal dispersion and an output transmission with multi-peaks. Therefore, we exploited the mode discrimination phenomenon using the bending loss, and the resulting S-bend resonator yielded an output transmission without multi-peaks. This phenomenon is utilized to remove higher-order modes efficiently using the difference in the effective refractive index between the higher-order and fundamental modes. As a result, the resonator achieved a Q-factor and sensitivity of 2.3 × 10 and 52 nm/RIU, respectively, using the variational finite-difference time-domain method. These results show that the multi-mode waveguide-based S-bend resonator with a wide line width can be utilized as a refractive index sensor.
本文提出了一种基于多模波导的光学谐振器用于集成光学折射率传感器。传统的光学谐振器已针对基于单模波导的谐振器进行了研究以提高性能，但由于纳米级结构的高制造成本，大规模生产受到限制。为克服这一问题，我们基于微尺度多模波导设计了一种S形弯曲谐振器。一般来说，多模波导不能用作光学谐振器，因为模态色散会导致性能下降以及输出传输呈现多峰。因此，我们利用弯曲损耗产生的模式辨别现象，所得的S形弯曲谐振器产生了无多峰的输出传输。利用高阶模与基模之间有效折射率的差异，该现象被用于有效去除高阶模。结果，使用变分有限差分时域方法，该谐振器分别实现了2.3×10的品质因数和52 nm/RIU的灵敏度。这些结果表明，具有宽线宽的基于多模波导的S形弯曲谐振器可用作折射率传感器。
