Design of a portable high-resolution Raman spectroscopic system based on Littrow configuration

Abstract

Raman spectroscopy has been widely applied in fields such as food safety, biomedicine, and deep-sea exploration due to its advantages of being non-destructive, requiring no sample pretreatment, and having low sensitivity to moisture interference. However, current portable Raman spectrometers generally suffer from insufficient resolution (6–12 cm⁻¹). The fundamental reason is that the compact optical path limits the rational configuration of optical component parameters, preventing the full utilization of the grating's dispersive power. To address these limitations, this paper proposes a design for a portable high-resolution Raman spectroscopic system based on a symmetrical Czerny-Turner structure, with the Littrow angle as the core design principle for grating incidence. Theoretical derivation demonstrates that the Littrow configuration effectively enhances the system's angular dispersion, diffraction efficiency, and imaging quality, which was further validated through simulations using Zemax software. A prototype was subsequently developed with overall dimensions of 180 mm × 160 mm × 55 mm. Testing with standard argon lamps and Raman samples shows that the prototype achieves a full-band resolution better than 5 cm⁻¹ and covers a Raman spectral range of 50–3500 cm⁻¹. The characteristic peaks of silicon wafers and ethanol are clearly resolved and consistent with standard spectra, verifying the feasibility and rationality of the system design.