Study of spurious optical signals in a fiber-optic Raman spectroscopy system

We have studied spurious signal effects in a typical configuration of a fiber-optic setup used for registering Raman scattering. In such a system, we have localized the most likely sources of interference that can affect the fluorescent, Raman, and laser signals. These parasitic artifacts are superimposed on the informative Raman signal from the sample, leading to false Raman bands in the spectrum recorded by the camera and a reduction in the signal-to-noise ratio. We measured the emission spectra of the probing diode laser. We also examined the Raman luminescence signals generated by the optical fibers with low-content hydroxyl groups and optical substrates of lenses and filters, such as BK7, CaF2, SiO2, MgF2, Al2O3. By successively analyzing the data obtained for each system component, we found that the lateral-longitudinal modes of the lasers with a volume Bragg grating cause one of the most substantial spurious signals. The presence of parasitic peaks in the recorded Raman spectrum has been experimentally confirmed in the example of crystalline silicon.