Cost-Effective Raman Spectra Acquisition Based on Spreading Code Modulation for Exciting Light

Abstract

Raman spectroscopy is a powerful, non-destructive analytical tool that is widely used across various fields for identifying molecular structures and reactions. However, Raman spectroscopy may be hindered by background and fluorescence noises. These noises are often stronger than Raman signals, causing complicated spectral interpretation. Therefore, a high signal-to-noise ratio (SNR) Raman spectrum is crucial for better identification accuracy. Currently, techniques can be used to amplify the Raman signal significantly, but often require significant time or complex hardware. Spread spectrum is a mature technology used in communication to suppress noise. This study introduces a method combining Raman signals with spreading codes to obtain cost-effective high SNR Raman spectra. Firstly, simulations were conducted to verify the spreading Raman spectrum with efficient computation. While the fluorescence and background noises were suppressed due to the cross-correlation properties of spreading codes. Next, a hardware environment comprised of a laser, polarization controller, and amplitude modulator was configured to demonstrate the feasibility of the spread spectrum Raman system. The measured Raman peaks from the samples are compared with the original Raman spectrum. The results demonstrate that the spread spectrum Raman system improves the SNR for both interleukin-6 and ink samples. The timing synchronization and code length estimation algorithms significantly simplify hardware design for engineering. Both simulation and experimental results validate that the SNR of the Raman system can be improved by using a spread spectrum technique. It allows Raman analysis for appropriate SNR with cost-effective hardware in the industry.