An On‐Chip Quad‐Wavelength Pyroelectric Sensor for Spectroscopic Infrared Sensing

Merging photonic structures and optoelectronic sensors into a single chip may yield a sensor‐on‐chip spectroscopic device that can measure the spectrum of matter. In this work, an on‐chip concurrent multiwavelength infrared (IR) sensor, which consists of a set of narrowband wavelength‐selective plasmonic perfect absorbers combined with pyroelectric sensors, where the response of each pyroelectric sensor is boosted only at the resonance of the nanostructured absorber, is proposed and realized. The proposed absorber, which is based on Wood's anomaly absorption from a 2D plasmonic square lattice, shows a narrowband polarization‐independent resonance (quality factor – Q of 73) with a nearly perfect absorptivity as high as 0.99 at normal incidence. The fabricated quad‐wavelength IR sensors exhibit four different narrowband spectral responses at normal incidence following the predesigned resonances in the mid‐wavelength infrared region that corresponds to the atmospheric window. The device can be applied for practical spectroscopic applications such as nondispersive IR sensors, IR chemical imaging devices, pyrometers, and spectroscopic thermography imaging.