Temperature decoupled silicon photonics based Fano resonance ion sensor

Abstract

A novel and compact ion sensor was developed by combining 2D plasmonic K${}_x$MoO₃ and Na${}_x$WO₃ with hexagonal channel and photonic crystal nanobeam cavity (PCNC) with Fano resonance. Fano resonance PCNC with a deterministic air mode (mirror period$>$gradient periodic region) and dielectric mode (mirror period$<$gradient periodic region) with a period of 180 nm were designed, which can be fabricated on multi project wafer (MPW) processing. The sensing system exhibits an refractive index (RI) and temperature sensitivity of 234.48 nm$/$RIU and 96 nm$/$K, respectively. Three PCNCs adopted wavelength division multiplexing over a wide range of wavelengths. Utilizing the near-infrared absorption of degenerated plasma K${}_x$MoO₃ and Na${}_x$WO₃ and its hexagonal ring-like ion sieve, a temperature decoupled Sodium (Na${}^{+}$) and potassium (K${}^{+}$) was achieved. Here, Fano resonance originates from interference between a bus waveguide with continue mode, inserted with two air holes, and the discrete state photonic crystal nanobeam cavity. This work paves the way to achieve an ultra-compact lab-on-chip resonance-based photonic building block.