Imaging-based intelligent spectrometer on a plasmonic rainbow chip

Article https://doi.org/10.1038/s41467-023-37628-0 Imaging-based intelligent spectrometer on a plasmonic rainbow chip Dylan Tua1,3, Ruiying Liu1,3, Wenhong Yang2,3, Lyu Zhou1, Haomin Song2, Leslie Ying 1 & Qiaoqiang Gan 1,2 Compact, lightweight, and on-chip spectrometers are required to develop portable and handheld sensing and analysis applications. However, the per- formance of these miniaturized systems is usually much lower than their benchtop laboratory counterparts due to oversimplified optical architectures. Here, we develop a compact plasmonic “rainbow” chip for rapid, accurate dual-functional spectroscopic sensing that can surpass conventional portable spectrometers under selected conditions. The nanostructure consists of one- dimensional or two-dimensional graded metallic gratings. By using a single image obtained by an ordinary camera, this compact system can accurately and precisely determine the spectroscopic and polarimetric information of the illumination spectrum. Assisted by suitably trained deep learning algorithms, we demonstrate the characterization of optical rotatory dispersion of glucose solutions at two-peak and three-peak narrowband illumination across the visible spectrum using just a single image. This system holds the potential for integration with smartphones and lab-on-a-chip systems to develop applica- tions for in situ analysis. Optical spectroscopy is one of the most widely used techniques for fundamental research as well as industrial processes. However, benchtop systems are usually bulky, expensive, and mainly designed for laboratory and industrial spectroscopic analysis. In recent years, researchers and major industrial players have shifted focus toward developing miniaturized, portable, and inexpensive spectrometer systems, which can enable many emerging applications for on-site, real-time, and in situ spectroscopic analysis in our daily lives1. For instance, 195 colloidal quantum dot filters with different optical transmission properties were placed on top of a smartphone camera chip2. By processing the large set of sensor readings, this chip-scale system can reconstruct the spectral features of incident light in the visible to near-infrared (IR) spectral range. Another pioneering work employed a single compositionally engineered nanowire as the key active element of an ultra-compact spectrometer chip3. Combined with extended post-data processing algorithms, the spectral response of the compact