A Concave Blazed-Grating-Based Smartphone Spectrometer for Multichannel Sensing

Abstract

A compact imaging smartphone spectrometer utilizing a lightweight aspheric concave blazed-grating is presented for multichannel spectral detection. The lightweight concave diffraction grating is fabricated on a plastic substrate using a two-step thermal-embossing method in a cost-effective and mass-productive way, which enables a large-area, smooth and aspheric concave surface while preserving a blazed-grating structure. The blazed-grating serves as a key single element for aberration-free light focusing and highly-efficient light diffraction. It thus eliminates extra moving optics in the spectrometer and improves the optical characteristics and system integration, which are proven by both simulation and experiments. Spectral linewidth of 1 nm is achieved by combining the concave grating with a smartphone camera. This compact imaging smartphone spectrometer is only about the size of a match-box. Spectra can be obtained directly from the detected images using a developed application (APP) interface. High-throughput plasmonic resonance sensing using microfluidic silver nanoslit arrays under various glycerin environments is demonstrated, and the detected resonance wavelength response is comparable with that detected by a commercial compact spectrometer.