Broadband Micro-Confocal Raman Spectrometer Using Four Tiled Sub-Gratings and Optimized Cylindrical Lens Correction

A micro-confocal Raman spectrometer is developed using four tiled sub-gratings, each with a groove density of 1200 lines/mm, and a single optimized cylindrical lens. The system achieves a broad Raman shift coverage from 99.8 to 4701 cm−1 with a spectral resolution of approximately 4 cm−1, and operates without any mechanical moving parts. The cylindrical lens corrects multi-channel astigmatism, compressing the spot size to one quarter of its original dimension and improving the signal-to-noise ratio by a factor of four. The prototype successfully detects Raman signals from silicon, sodium nitrite, cyclohexane, and sodium sulfate solutions with concentrations as low as 0.01 mol/L. It also resolves inorganic mixtures, minerals including celestine, rhodonite, and calcite, as well as microplastics such as polyamide, polytetrafluoroethylene, polyethylene, and styrene-ethylene-butylene-styrene block copolymer. These results demonstrate that the spectrometer offers reliable qualitative and quantitative detection capabilities with both broad spectral bandwidth and high resolution.