A compact Raman laser gas spectrometer is developed. It comprises a high-power green laser at 532.123 nm as an excitation source and a specially designed gas cell with an internal volume of less than 0.6 cm3 that can withstand gas pressures up to 100 atm. The resolution of the spectrometer is ~1 cm−1. The Raman spectra of chemically pure isotopically enriched carbon dioxide (12CO2, 13CO2) and methane (12CH4, 13CH4) gases are studied. The expected limit of detection (LOD) is less than 100 ppm for the isotopologues of CO2 and less than 25 ppm for those of CH4 (at a gas pressure of 50 atm.), making the developed spectrometer promising for studying the sources of emissions of greenhouse gases by resolving their isotopologue composition. We also show the suitability of the spectrometer for Raman spectroscopy of human exhalation.

Proton exchanged LiNbO3 waveguides are studied using Raman spectroscopy. Depending on the waveguide mode, the spectra resemble those of pure LiNbO3 at high temperatures. A characteristic peak appears at 69 cm-1 which is probably due to second-order Raman scattering but strongly associated with the presence of protons. It is proposed that the change in the Raman spectra is due to the coexistence of the ferroelectric and paraelectric phases of LiNbO3 at room temperature, induced by the proton exchange deformations on the lattice.

We demonstrate the possibility of applying surface-enhanced Raman spectroscopy (SERS) combined with machine learning technology to detect and differentiate influenza type A and B viruses in a buffer environment. The SERS spectra of the influenza viruses do not possess specific peaks that allow for their straight classification and detection. Machine learning technologies (particularly, the support vector machine method) enabled the differentiation of samples containing influenza A and B viruses using SERS with an accuracy of 93% at a concentration of 200 μg/mL. The minimum detectable concentration of the virus in the sample using the proposed approach was ~0.05 μg/mL of protein (according to the Lowry protein assay), and the detection accuracy of a sample with this pathogen concentration was 84%.

A Raman gas analyzer for detecting carbon isotopologues with an excitation laser with a power of 5 W, generating at a wavelength of 532 nm, focusable in a waist of 7 μm using a lens with compensation for spherical aberration is presented. The signal is detected by a high-resolution spectrometer with a matrix cooled to -40° C. The program optimization of the system parameters is presented: focusing lens, cuvette windows.

The possibility using Raman spectroscopy in the analysis of samples for the urease breath test to diagnose the presence of the bacterium Helicobacter pylori has been demonstrated. The Raman scattering spectra of the air exhaled by a person were obtained, the volume fractions of 12CO2 and 13CO2 in exhalation samples were determined.