Integrated solid immersion grating microspectrometer with wedge prism correction for visible and near-infrared spectroscopic applications.

For compact spectrometers, the enduring technical challenge lies in the simultaneous optimization of high optical performance and miniaturization. Here we report a solid immersion grating microspectrometer with wedge prism correction (SIG-W-µSPEC), which realizes both high spectral resolution and a highly compact structure across a broad spectral range. The SIG-W-µSPEC integrates a solid immersion grating (SIG), planar reflectors, an optical wedge, a convex lens, a silicon microslit, and a CMOS linear array sensor into a single optical module. The SIG endows the system with high angular dispersion but inevitably induces focal plane tilt; the optical wedge not only compensates for this tilt with high precision but also effectively compresses the optical path length. Following high-precision encapsulation, the SIG-W-µSPEC achieves an average spectral resolution of 4.4 nm in the 600-1000 nm wavelength range, with an overall volume of merely 0.63 cm3. We applied this device to collect the reflectance spectra of fruits for the prediction of soluble solids content (SSC), yielding a high correlation coefficient (R2=0.941). This ultra-compact spectrometer demonstrates broad application prospects in diverse fields, including agricultural quality monitoring, biomedical sensing, and real-time non-invasive on-site detection.