On-Chip Chemical Sensing Using Double-Slot Silicon Waveguide
Sushma Gali, Akshay Keloth, Shankar Kumar Selvaraja
Abstract
In this article, we present refractive index measurement using a double-slot silicon waveguide-based Mach–Zehnder interferometer (MZI). We present a double-slot waveguide that offers the best sensitivity and limit of detection (LOD) compared to wire and single-slot waveguides. We demonstrate ultralow loss coupling between a single-mode waveguide and a double-slot waveguide and experimental proof for double-slot excitation. The double-slot waveguide is used to demonstrate a highly sensitive concentration sensor. An unbalanced Mach–Zehnder is used as the sensor device to demonstrate concentrations of potassium chloride (KCl) in deionized water. A sensitivity of 700 nm/RIU and a LOD of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.142\times 10^{-{6}}$ </tex-math></inline-formula> RIU are achieved experimentally. To the best of our knowledge, the demonstrated sensitivity is the highest for an ON-chip-guided waveguide sensing scheme. Index Double-slot waveguide, evanescent field, Mach–Zehnder interferometer (MZI), ON-chip, refractive index, sensitivity.