Refractive Index Sensor Based on Leaky Resonant Scattering of Single Semiconductor Nanowire

Optical refractive index (RI) sensors, with the advantages of fast response, resistance to electromagnetic interference, and more options for signal collection, are widely used in biological fields. Compared with the metallic nanoparticle RI sensors based on localized surface plasmon resonance (SPR), nonmetallic nanomaterial RI sensors based on leaky resonant scattering have the advantages of high sensitivity, large sensing volume, good reliability, and more suitability for biosensing. However, so far studies on nonmetallic nanomaterial RI sensors are less reported. In this work, we study semiconductor nanowire (NW) RI sensors using a CdSe nanowire as an example. The NW diameter and substrate effects on the sensitivity of the RI sensors are investigated experimentally and theoretically. The bulk wavelength sensitivity of a suspended NW can be as high as 235 nm/RIU (per refractive index unit), and the highest figure of merit is 4.6. The larger decay length (∼100 nm) of the NW sensor enables greater sensing...