Responsible for the facility:
Grigory M. Arzumanyan
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Tel. +7 (496) 216-50-69
Kahramon Z. Mamatkulov
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Tel. +7 (496) 216-49-53
Main research areas:
- Spectroscopy and microscopy of spontaneous and stimulated Raman scattering of light.
- High contrast non-linear imaging.
- Registration of single molecules.
- Direct photo- and upconversion luminescence.
- Working with living cells.
- Lipid-protein interactions.
- Spectroscopy of programmed cell death
- Raman markers in biomedicine.
Facility:
The basic facility for research implemented at the Sector of Raman Spectroscopy (Centre "Nanobiophotonics") is a multimodal optical platform based on a laser, confocal "CARS" microscope that allows to carry out spectroscopy and microscopy study of various materials (solids, liquids, powders, biological samples and others) based on spontaneous Raman scattering (RS) of light, giant Raman scattering (GRS, SERS), as well as stimulated coherent amplification of light scattering.
Overview of the CARS microspectrometer 
The discovery of laser sources of radiation in the early 1960s stimulated greatly research on nonlinear optical and resonance methods for analysing matters. For the excitation of nonlinear signals, high-intensity picosecond or femtosecond lasers are used that can simultaneously initiate several nonlinear optical phenomena: harmonic generation (SHG, THG), multiphoton and up-conversion luminescence, coherent anti-Stokes light scattering (CARS), and others.
CARS is a third-order nonlinear optical process involving interactions between pump beams with a frequency ωn, a Stokes wave with a frequency ωs and the resulting CARS signal at an anti-Stokes frequency ωac = 2ωn – ωs, generated towards the phase matching. Vibrational contrast in the CARS process is produced when the frequency difference Δω=ωn-ωc between the pump and the Stokes beam is tuned to resonance with the vibrational mode of the selected chemical bond. In this case, resonant oscillations are coherently generated using excitation fields, thereby creating an intense and directional anti-Stokes signal compared to a weak spontaneous Raman signal (most molecules possess a small RS cross section ~ 10-30 to 10-25 cm2). CARS signals are 3-4 orders of magnitude more intense than those of the spontaneous Raman scattering processand and allow to obtain chemically selective high-contrast images.
Optical schematic of the basic components and architecture of the CARS microspectrometer 
To generate CARS signals, a picosecond laser Nd:YVO4 (Ekspla, PT257-SOPO, Lithuania) tunable in wavelength (690–990) nm with a pulse duration of 6 ps and a pulse repetition rate of 85 MHz has been installed on the optical platform of the confocal laser microscope. This laser serves as a source of both a Stokes wave and, simultaneously, a wavelength-tunable pump generated using an intracavity optical parametric oscillator (OPO) with a maximum power of 200 mW and a line width of ~6 cm-1. Depending on the analyzed sample, three lasers are used to generate a spontaneous Raman signal: a He-Ne laser (633 nm) and two diode-pumped lasers at wavelengths of 532 nm and 785 nm.
In order to achieve ultrahigh sensitivity of registration of Raman spectra from molecules of low concentration analytes, up to the level of single molecules, various SERS-active substrates are used, both commercial and developed at BSUIR, Minsk, Belarus.
The main characteristics of the “CARS” microscope Basic functional modalities Spontaneous Raman, F-CARS, E-CARS, P-CARS, GRS, GCARS, up-conversion luminescence Lasers for spontaneous RS 532nm (20mW), 633nm (15mW), 785nm (100mW) Laser for exciting the CARS signal Picosecond laser Nd:YVO4, Ekspla, PT257 + SOPO Stokes wave: 1064 nm, 6 ps, 5 W Pulse repetition frequency: 85 MHz Tunable pump wave: 690 - 990 nm, 150-300 mW. Mode composition: TEM00 Polarization: horizontal Signal registration Four channels for high-speed measurements (PMT) and a channel with a CCD camera Spectral registration range Raman signal: 50 – 6000 cm-1 CARS signal: 990 - 5000 cm-1 Spectral resolution Raman signal: 0.9 cm-1 (grating 1200 pcs/mm) CARS signal: 7-8 cm-1 Spatial resolution Raman signal: XY < 300 nm, Z ~ 700 nm CARS signal < 0.7 µm Speed scan range With a 60x lens: XY: 225 x 225 µm Z: 80 µm Spectral measurements and imaging Imaging monochromator-spectrograph MS5004i Digital CCD camera, Proscan, HS 101H Control and automation Complete automation
*Testing mode