Portable Differential Raman Spectrometer with Fluorescence Suppression for Field Analysis

1. Differential Raman spectroscopy technology, effectively eliminates fluorescent background;

2. Dual-band Laser coupling technology;

3. High sensitivity and TE-Cooled CCD;

4. IP67 dustproof and waterproof industry protection;

5. Ultra low noise circuit;

6. Android operating system;

7. Powerful embedded software with User-Friendly Interface;

8. The 11.6-inch capacitive touch screen supports multi-touch control;

9. Search and display peak easy;

10. Battery>4h;

11. Support LAN remote control;

12. USB 2.0；

13. Effectively suppress fluorescence interference;

14. Delivers stable, reliable performance for field and laboratory use.

Differential Raman spectroscopy, also called shifted excitation Raman difference spectroscopy (SERDS), uses two lasers with slightly different wavelengths to irradiate the sample to obtain two original Raman spectra. The fluorescence background does not shift with minor changes in laser wavelength, while the position of the Raman peak changes significantly. Subtracting these two spectra yields a differential spectrum where the fluorescence background cancels out entirely, eliminating fluorescence interference.

Fig. 1 (a) Raw Raman spectra (solid and dotted lines represent the Raman spectra excited by 784.5nm and 785.5nm laser respectively); (b) Differential spectra

Under ideal conditions, normal Raman spectra can be readily recovered from differential spectra using accumulation and convolution methods. However, actual measured spectra contain various noise sources, such as photodetector dark current noise, circuit thermal noise, ambient background light noise, and internal spectrometer stray light. Noise not only reduces measurement signal-to-noise ratio (SNR) but also impairs the performance of restoration algorithms. Compared with laboratory Raman systems, portable Raman spectrometers have lower SNR and face more severe noise interference. In addition to noise, practical differential spectra may exhibit inconsistent and asymmetric positive and negative peak intensities, further reducing restoration algorithm efficacy. Raman signal intensity is inversely proportional to the fourth power of the wavelength; even the minor difference between the two SERDS excitation wavelengths can cause Raman peak asymmetry. Noise superimposition on peaks, sample temperature differences post-irradiation, and subtle fluorescence characteristic changes (photobleaching effect) during dual measurements can also induce peak asymmetry.