Functional demonstration of a compact silicon diffractive sensor for toluene

Abstract

A compact silicon diffractive sensor detecting toluene in solution is demonstrated. This sensor is fabricated in silicon-on-insulator and utilizes a standard telecommunications wavelength. In-plane diffraction gratings enable micrometer-scale device sizes and intensity-based (as opposed to spectral-based) detection for increased integrability. Precise grating design enables 2-D sensor arrays without the addition of separate optical splitters. Detection of the relative diffracted and transmitted intensities is independent of attenuation and is thus robust. This proof-of-concept sensor is shown to measure toluene concentrations as low as 100 parts per million, corresponding to a refractive index change of 3×10(-4). In addition, a linear sensor array with individual sensor addressability and 2-D array capability is demonstrated. The characteristics of this sensor type make it promising for field-deployable lab-on-a-chip applications.