A silicon-based compact comb-like asymmetric grating is proposed as a thermally stable optical filter for label-free sensing applications. The device is designed and fabricated with a cavity section introduced between the two grating regions which are partially etched in the lateral direction to ensure the nonzero coupling of the fundamental and first-order modes in the propagation and counter-propagation direction. To demonstrate refractive index sensing, resonance shift in the device is measured with sodium chloride (NaCl) dissolved in DI water. In contrast to conventional Bragg grating where stopband lies in the transmission spectrum, the proposed device allows a single narrow passband transmission peak with a large Free Spectral Range (FSR) attributed to the engineered photonic bandgap of two modes present in the waveguide region. The device is deliberately designed such that slightly wide resonance peak is obtained that makes device operation thermally stable for a large temperature variation of ±15 K. A higher-order leaky mode with strong light-analyte interaction (due to long corrugation width) in the gratings governs high sensitivity of ≈352 nm/RIU for different concentrations of NaCl from 0% to 10% in the Deionized (DI) water with a small footprint area of $18~{\mu } {m}^{\textsf {2}}$ only. Proposed filter characteristics are well suited for multifunctional applications in integrated photonic devices.

中文翻译：

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使用硅基梳状非对称光栅进行传感应用的热稳定光学滤波

提出了一种基于硅的紧凑型梳状非对称光栅作为用于无标签传感应用的热稳定滤光片。该器件的设计和制造在两个光栅区域之间引入了一个空腔部分，在横向方向上部分蚀刻，以确保基本模式和一阶模式在传播和反向传播方向上的非零耦合。为了演示折射率传感，装置中的共振位移是用溶解在去离子水中的氯化钠 (NaCl) 测量的。与阻带位于传输光谱中的传统布拉格光栅相比，所提出的器件允许单个窄通带传输峰值具有较大的自由光谱范围 (FSR)，这归因于波导区域中存在的两种模式的工程光子带隙。该器件经过精心设计，以获得稍宽的共振峰，使器件在 ±15 K 的大温度变化下具有热稳定性。 高阶泄漏模式具有强光与分析物相互作用（由于长波纹宽度）对于去离子 (DI) 水中从 0% 到 10% 的不同浓度的 NaCl，光栅控制 ≈352 nm/RIU 的高灵敏度，占地面积小，仅为 18 美元~{\mu } {m}^{\textsf {2}仅}$。提议的滤波器特性非常适合集成光子器件中的多功能应用。光栅中具有强光-分析物相互作用（由于长波纹宽度）的高阶泄漏模式控制着对去离子 (DI) 水中从 0% 到 10% 的不同浓度 NaCl 的 ≈352 nm/RIU 的高灵敏度。仅 $18~{\mu} {m}^{\textsf {2}}$ 的小占地面积。提议的滤波器特性非常适合集成光子器件中的多功能应用。光栅中具有强光-分析物相互作用（由于长波纹宽度）的高阶泄漏模式控制着对去离子 (DI) 水中从 0% 到 10% 的不同浓度 NaCl 的 ≈352 nm/RIU 的高灵敏度。仅 $18~{\mu} {m}^{\textsf {2}}$ 的小占地面积。提议的滤波器特性非常适合集成光子器件中的多功能应用。