Since January 2015 a new structural division – Sector of Raman spectroscopy (Centre “Nanobiophotonics”) – has started its activities at FLNP. Studies are performed within the JINR theme “Multimodal platform for Raman and nonlinear optical microscopy and microspectroscopy for condensed matter studies”.

Along with neutron and synchrotron research, Raman spectroscopy and microscopy occupy its own niche in the study of properties, structure and diagnostics of condensed matter. Raman spectroscopy refers to scattered light from a sample that exhibits a frequency shift reflecting the energy of specific molecular vibrations within the sample of interest. In this manner, it provides a detailed chemical composition of the sample – a chemical fingerprint in essence. The technique has wide potential in the biomedical sciences as it may be applied to samples over a wide size range from single cells through to intact tissue. One of the major challenges of Raman spectroscopy is the extremely low intensity of the emitted signal. Thus, considerable effort has focused on enhancing the ratio of signal to background noise including the CARS (Coherent antiStokes Raman Scattering) and SERS (Surface Enhanced Raman Scattering) enhanced options of the spontaneous Raman scattering.

CARS microscopy provides an advanced, minimally invasive (nondestructive) and label-free technique with high sensitivity and high lateral spatial resolution capable of selective chemical imaging of major types of macromolecules: proteins, lipids, nucleic acids, etc. Like spontaneous Raman, CARS probes vibrational modes in molecules and does not require exogenous dyes or markers, which is advantageous in imaging small molecules for which labeling may strongly affect their molecular properties.

The advantages of CARS spectroscopy: since an anti-Stokes wave is generated at higher frequencies (shorter wavelengths shifted to the blue region) there is practically no effect of luminescence and the vibrational modes of molecules are most pronounced. In addition, scattering on phase-matching coherently excited vibrations leads to a significant increase (by several orders of magnitude) in the intensity of scattered light as compared with that of spontaneous Raman scattering. Furthermore, when studying samples both in the mode of spontaneous scattering and CARS spectroscopy there is no need for fluorescent labels which always cause photobleaching. Also, using for pumping lasers emitting in the near-IR region, CARS is also a noninvasive method for studying samples, which is especially important when analyzing biological samples. It also should be noted that CARS microscopy allows us to realize high-speed recording of spectrally selective images, corresponding to specific vibrational states of molecules. All these advantages have made CARS spectroscopy and microscopy a highly effective and promising analytical method and tool widely used in various fields of natural and applied sciences (chemistry, physics, biomedicine, pharmaceuticals, materials science, geology, and others).

SERS is a plasmonic-based process characterized as a label-free and high-sensitive spectroscopy. This technique was developed to detect extremely small quantities of molecules (up to the single-molecule level) by determining their characteristic Raman signal. The high sensitivity of SERS is mainly due to electromagnetic interaction given by an effective, evanescent field enhancement on the metal surface based on the excitation of surface plasmon-polariton modes. By generating metallic nanostructures with different shapes/dimensions, it is possible to tune the plasmon resonance.