Alexey Fedorovich Bunkin

• Russian Academy of Sciences

Spectroscopy experiments of the inelastic scattering of laser pulses in an aqueous suspension of silicon dioxide (SiO 2 ) nanoparticles at room temperature have revealed for the first time that the centroid of the OH Raman scattering band is shifted to the pump line up to 10 cm –1 and two components of stimulated backward and forward Brillouin scat...

The impact of gating conditions, self-absorption effect and plasma temperature fluctuations on laser induced breakdown spectroscopy (LIBS) signals distribution functions have been studied in detail since analysis accuracy (error of concentration determination) and sensitivity (limits of detection) are defined by the analytical signal distribution f...

A lidar backscattering signal from an opaque target object, passed through a 9-m water layer with scattering meshes on the laser beam path, has been detected (for the first time, to the best of our knowledge) when sensing by pulses with eye-safe radiation energy density (~1 μJ/cm2). The new principle of laser sensing makes it possible to measure th...

The propagation of a linearly polarized transverse sound wave in a semiconductor layer with a certain crystallographic structure with a sufficiently high concentration of conduction electrons is considered. The semiconductor layer is located in a spatially uniform magnetic field directed perpendicular to the plane of incidence of the sound wave and...

Fossilized plant remains have been studied simultaneously by laser induced fluorescence and Raman spectroscopies, to reveal the prospective methods for onsite or/and laser remote sensing in future extraterrestrial missions. A multiwavelength instrument, capable of fluorescence and Raman measurements, has been utilized for the study of isolated plan...

The impact of the laser spot dimensions on the laser-induced breakdown spectroscopy (LIBS) analysis of heterogeneous samples was studied in detail. The study was stimulated by comparing the analytical performance of three LIBS instrument types that have potential utilization at different stages of agricultural material control: a hand-held analyzer...

A physical mechanism of stimulated light scattering on nanoscale objects in a water suspension is proposed. The proposed mechanism is based on the dipole interaction between the light wave and the inevitable uncompensated electrical charge on a nanoscale object (e.g., a virus or nanoparticle) in a water environment. Experimental data on the tobacco...

The laser induced fluorescence spectroscopy was systematically utilized for remote sensing of different soils and rocks for the first time, to the best of our knowledge. Laser induced fluorescence spectroscopy measurements were carried out by the developed nanosecond LIDAR instrument with variable excitation wavelength (355, 532 and 1064 nm). LIDAR...

A simple physical mechanism of stimulated light scattering on viruses in a water suspension (similar to Langmuir wave mechanism in plasma) is proposed. The proposed mechanism is based on the dipole interaction between the light wave and the inevitable uncompensated electrical charge on a virus in a water environment. Experimental data on tobacco mo...

A stimulated low-frequency Raman scattering signal with frequencies of about 31.17 and 43.5 GHz caused by the presence of natural vibrational frequencies of the studied tobacco mosaic virus particles is detected in a suspension of the tobacco mosaic virus at the suspension particle concentrations of about 10¹² and 2.0 × 10¹² cm–3. A change in the s...

A simple physical mechanism of stimulated light scattering on nanoscale objects in water suspension similar to Langmuir waves mechanism in plasma is proposed. The proposed mechanism is based on a dipole interaction between the light wave and the non-compensated electrical charge that inevitably exists on a nanoscale object (a virus or a nanoparticl...

Both backward and forward directed Stimulated Brillouin Light Scattering (SBLS) are observed in an aqueous suspension of SiO2 nanoparticles with diameters of 100 and 200 nm by using for excitation a second harmonic (λ = 532 nm, 10 ns) of a single (∼0.005 cm − 1) mode YAG : N d 3 + laser. Both backward and forward directed SBLS are characterized by...

A paradoxical decrease in the generation threshold of high Stokes and anti-Stokes components of stimulated Brillouin scattering in water has been detected for the first time to our knowledge upon the displacement of the caustic of a focused laser beam from the bulk of water to air. The mechanism of generation of components caused by the four-wave m...

It has been demonstrated for the first time that pulsed laser Raman spectroscopy can be used for diagnostics of a local acoustic pressure profile with a peak pressure drop of 50 MPa and a carrier frequency of 2.0 MHz in the focus of an ultrasound beam propagating in water. A 527-nm 10-ns laser pulse has been focused into the waist of the ultrasound...

Dynamics of a suspension of dielectric nanoparticles in an intense laser field is considered for the first time. A two-dimensional model is developed for interaction of laser radiation with nanoparticles in a suspension. A stable spatial configuration of nanospheres in a suspension is found and dispersion relations for low-lying excitations of a mu...

A low-frequency stimulated scattering (LFSS) signal caused by pulsations of nanospheres under an electromagnetic field is detected in an aqueous suspension of dielectric nanospheres of three diameters (∼74 nm, ∼292 nm, and ∼540 nm) at various particle concentrations. The frequency shifts of the scattering line, calculated based on the developed mod...

Excitation of coherent vibrations of different-sized polystyrene nanospheres at their acoustic eigenmodes in aqueous suspensions is observed in the laser pulse field. To substantiate the observed features, a model of interaction of an electromagnetic field with a dielectric in heterogenous media is developed which allows eigenmodes of nanospheres i...

Stimulated low-frequency scattering of light by aqueous suspensions of the tobacco mosaic virus with the scattering frequency depending on the concentration of the virus is observed for the first time. For concentrations of ∼1 × 10¹² and ∼2 × 10¹² cm–3, the Stokes components of scattered light are shifted by ∼43.99 and ∼31.08 GHz, respectively. At...

A considerable increase in the concentration of H2O ortho spin isomers and H2O2 molecules in the hydration layer at the interface of water and molecules of DNA, denatured DNA, and protein α- chymotrypsin is found using low-frequency laser spectroscopy of four-photon scattering (FPS). Spectra of rotational resonances of H2O ortho and para spin isome...

Coherent radiation at the wavelength of stimulated Brillouin scattering concurrent with the incident laser beam has been observed for the first time in the aqueous suspension of dielectric nanospheres with an average diameter of about 290 nm at their concentration ranging from about 10⁹ to 10¹¹ cm−³. The theory of the phenomenon is constructed.

For the first time, stimulated Brillouin scattering (SBS) spectra have been measured for a suspension of dielectric nanoparticles in water. We observed anomalous dependence of SBS spectra on the concentration of polystyrene nanospheres (74 nm diameter). The nonlinear five-fold increase in the SBS threshold was determined for the nanosphere concentr...

The four-photon low-frequency light scattering by acoustic vibrations of elastic inclusions in a liquid heterogeneous medium has been investigated. General expressions are obtained for the amplitude of electromagnetic wave generated in the field of specified two-frequency (Raman) optical pumping under conditions of induced longitudinal acoustic vib...

When low-frequency stimulated Raman scattering (SRS) is excited in the tobacco mosaic virus (TMV) suspension, an anomaly in the scattering line frequency shift is detected, i.e., the dependence on the concentrations of TMV and tris-buffer as the TMV concentration increases. An explanation of the phenomenon, based on the idea of the formation of the...

The stimulated low-frequency Raman scattering at acoustic vibrations of elastic inclusions in a liquid heterogeneous medium placed in an external open optical cavity has been investigated. The amplitudes of stationary field oscillations in the cavity at the frequencies of the excitation and the first Stokes component are found within a two-dimensio...

The interaction of laser pulses with the Cauliflower mosaic virus (CaMV) in a Tris-HCl pH7.5 buffer is investigated. 20 ns ruby laser pulses are used for excitation. Spectra of the light passing through the sample and reflected from it are registered with the help of a Fabri-Perot interferometer. Stimulated low-frequency Raman scattering (SLFRS) in...

The interaction of laser pulses with the Cauliflower mosaic virus (CaMV) in a Tris-HCl pH7.5 buffer is investigated. 20 ns ruby laser pulses are used for the excitation. Spectra of the light passing through the sample and reflected from it are registered with the help of a Fabri-Perot interferometer. Stimulated low-frequency Raman scattering (SLFRS...

Lidar sensing of tectonic aerosol fluctuations in the laser strainmeter–interferometer tunnel during 2017.12–2018.05 at the Schultz cape (131°9′8″ E, 42°34′6″ N) near Vladivostok was performed for the first time to our knowledge. A negative correlation of laser interferometer and aerosol lidar signals was observed during low-frequency Earth crust d...

A low-frequency SRS (LFSRS) signal is detected at a certain dielectric nanoparticle (latex spheres) concentration in an aqueous suspension. The SRS line shift is close to its estimate by the “transverse” hypersound speed in latex.

Spectra of coherent scattering at four-wave mixing of two diode laser radiation in liquid suspensions of dielectric nanoparticles are obtained for the first time. Dependence of the scattering resonance width on the concentration of nanoparticles in the suspension is studied. It is shown that the experimentally observed dependences of the width of t...

A theory of generation of anti-Stokes radiation on the eigenvibrations in a suspension of cylindrical nanoparticles in the field of two copropagating electromagnetic pump waves has been developed. Surface ponderomotive forces are shown to induce acoustic vibrations and dipolemoments of nanoparticles at the anti-Stokes frequency. Under these conditi...

Detection of ship wakes is utterly important for ship traffic monitoring, security of sea borders, etc. Among standard detection methods there are radar and acoustic sensing, photographing, hyperspectral measurements, and water sample analysis. However, these methods are hardly suitable for detecting wakes of light high-speed boats. An alternative...

Multilayer tungsten carbide wear resistant coatings were analyzed by laser induced breakdown spectroscopy (LIBS) and energy dispersive X-ray (EDX) spectroscopy. Coaxial laser cladding technique was utilized to produce tungsten carbide coating deposited on low alloy steel substrate with additional inconel 625 interlayer. EDX and LIBS techniques were...

Laser remote sensing of an algal bloom in a freshwater reservoir on the Volga River in central Russia was carried out. The compact Raman lidar was installed on a small ship to probe the properties of the surface water layer in different typical regions of Gorky Water Reservoir. Elastic and Raman scattering as well as chlorophyll fluorescence were q...

Remote water temperature measurements by Raman scattering is a perspective tool for in situ and/or real-time studies for inaccessible areas such as the Arctic region. State-of-the-art laser remote temperature detection techniques are based on temperature-dependent transformation of the Raman OH stretching vibration band. This study compared differe...

Single vs multimode laser beams were compared for double pulse laser ablation, plasma properties and laser induced breakdown spectroscopy (LIBS) analytical capabilities. Laser beams with Gaussian and multimode profiles were generated within the same Nd:YAG laser in single and double pulse regimes. Gaussian beam produced a small and deep crater whil...

A scheme of nonlinear optical four-wave mixing of two counterpropagating laser beams on the surface of a semiconductor is proposed and analyzed. It is shown that the density modulation of the electron-hole plasma current carriers in the light-induced grating manifests itself in the probe beam depolarization signal after the reflection from the surf...

Spectra of scattering on surfaces of semiconductors are obtained using the four-wave scheme of laser beam interaction. A considerable difference in the shape of the scattered signal is observed when the circular polarization vector of the pump beam rotates in two opposite directions.

Probe-beam scattering spectra have been obtained for four-wave mixing of laser waves in the skin layer of intrinsic semiconductors. The spectra were recorded using the frequency dispersion of orthogonally polarized radiation, which arises as a result of nonlinear optical interaction with conduction-band electrons. The mixing of two counterpropagati...

Two concentration ranges (from 10−5 to 10−9 and from 10−13 to 10−18 M) corresponding to enhanced fluctuations of Rayleigh and Raman scattering of second-harmonic (527 nm) pulses of YVO4:Nd3+ laser are found for aqueous solutions of antioxidant potassium phenosan. A correlation is revealed between the rise in elastic Rayleigh scattering intensity an...

A nonmonotonic bimodal dependence of elastic, Rayleigh scattering on the potassium phenosan concentration in an aqueous solution has been revealed. A similar dependence has been found, for the first time, for scattering amplitude fluctuations. The observed correlation is indicative of structural transitions in hydration shells of potassium phenosan...

The Raman scattering signal at the second harmonic (532 nm) of cw Nd:YAG laser in a 0.5-μm-thick methyl hydroxyethyl cellulose film on a gold substrate is found to be attenuated when a platinum-iridium probe (with a tip radius of about 10 nm) of a scanning tunnel microscope is brought close (at a distance of 6 to 8 nm) to the surface. The fluoresce...

Express diagnostics of large freshwater reservoirs is of great interest for both scientists and local authorities especially within a summer period due to rapid growth of phytoplankton (so-called algal bloom). Points of interest include changes of natural ecosystems and fresh water supply quality control during algal bloom. Conventional contact met...

A comparison of laser ablation by a train of picosecond pulses and nanosecond pulses revealed a difference in laser craters, ablation thresholds, plasma sizes and spectral line intensities. Laser ablation with a train of picosecond pulses resulted in improved crater quality while ablated mass decreased up to 30%. A reduction in laser plasma dimensi...

A new mechanism of optical nonlinearity of intrinsic semiconductors is proposed, which is based on bandgap modulation due to the four-wave mixing of interacting waves on the semiconductor surface. This phenomenon is theoretically considered within a one-dimensional model. The corresponding resonances are experimentally found in Ge and Si samples.

An efficient and simple and convenient technique for transparent samples thickness measurements by Raman spectroscopy is suggested. The elastic scattering can be effectively used for sample border indication if the refractive index changes more than 3%, while it fails to detect an ice-to-water border of floating ice. The alternative is to use Raman...

There are a number of aqueous-soluble high-molecular compounds, the biochemical activity of which has a nonmonotonic character in dependence on the concentration. It should be noted that the DLS provides the measurement of the radius of correlations of fluctuations of the refractive index of a substance, which coincides in the case of suspensions o...

Single- and multi-shot femtosecond laser surface ablation of a single-wall carbon nanotube-based substrate at 515- and 1030 nm wavelengths was studied by scanning electron microscopy and micro-Raman spectroscopy. The laser ablation proceeds in two ways: as the low-fluence mesoscopic shallow disintegration of the surface nanotube packing, preserving...

A compact Raman LIDAR system with a spectrograph was used for express ice thickness measurements. The difference between the Raman spectra of ice and liquid water is employed to locate the ice–water interface while elastic scattering was used for air–-ice surface detection. This approach yields an error of only 2 mm for an 80 mm thick ice sample, i...

The concentration dynamics of the scattering spectral width in a number of binary solutions has been studied by four-wave mixing spectroscopy near the Rayleigh resonance. It is noted that, according to the classical concepts, a variation in the correlation length of fluctuations of the relative concentration of molecules in a solution plays a key r...

Results of theoretical and experimental investigations of the nonlinear mechanism of Rayleigh-wing formation during the four-wave mixing process in suspensions are presented. The developed theory shows that simultaneous action of two laser radiations with different wavelengths on a spherical particle in a viscous liquid causes a nonlinear resonant...

The Rayleigh resonance in binary solutions was studied by four-wave mixing light scattering spectroscopy for the first time. A hysteresis-like dependence of the resonance linewidth on the concentration was found.

We have proposed a mechanism of coherent modulations of the P* state in the transient absorption spectra of the reaction centers isolated from purple bacteria. Two water molecules, located between special pair, Ba, Bb chlorophylls and histidine L175 and M202, are supposed to be the ortho-H2O and para-H2O isomers with different magnetic properties....

A method for switching the regime of single-frequency generation of nanosecond pulses to a train of picosecond pulses in the Nd:YAG laser with an electro-optic Pockels Q-switch without changing cavity elements is proposed. The single-frequency regime was provided by aligning an active element which played the role of a longitudinal cavity mode sele...

The space-time dynamics of thermal melting, subsurface cavitation, spallative ablation, and fragmentation ablation of the silicon surface excited by single IR femtosecond laser pulses is studied by timeresolved optical reflection microscopy. This dynamics is revealed by monitoring picosecond and (sub)nanosecond oscillations of probe pulse reflectio...

A simple and convenient procedure for single-shot, single-spot ablation threshold measurement has been developed. It is based on the employment of cylindrical lens to obtain elliptical Gaussian laser spot. The ablated spot chords which are parallel to the minor axis were measured across the spot major axis which is proportional to the fluence cross...

Compact Raman LIDAR system for remote sensing of sea, snow and ice was developed in Wave Research Center at Prokhorov General Physics Institute of RAS. Diode pumped solid state laser (532 nm, 5 ns, 200 μJ/pulse, 1 kHz) in combination with grating spectrograph equipped with gated detector (ICCD) resulted in high sensitive detection in wide spectral...

We consider the dynamics of H{sub 2}O monomers in channels of icelike structures using the model of 1D rotator (i.e., a particle with one translational and one rotational degree of freedom). The effect of the channel walls on the motion of the particle is simulated by the interaction of the dipole moment of the particle with a periodic electric fie...

A new method of non-linear laser spectroscopy based on four-wave scattering of pump laser radiation into the probe laser cavity is suggested and realized. As a result of intracavity amplification there is an opportunity to investigate weak narrow resonances of different types including the resonances of photo-elastic scattering in optical materials...

A steady-state self-consistent lasing regime in a laser cavity is investigated with allowance for the back action of the output radiation at four-wave low-frequency scattering in the external sample. The scattering is by the photoelastic potential in the field of the additional opposing laser. General expressions for steady-state amplitudes of fiel...

A compact Raman lidar system for remote sensing of sea and drifting ice was developed at the Wave Research Center at the Prokhorov General Physics Institute of the Russian Academy of Sciences. The developed system is based on a diode-pumped solid-state laser combined with a compact spectrograph equipped with a gated detector. The system exhibits hi...

A physical mechanism of the deviation of plasma composition from stoichiometry during laser ablation of multicomponent alloys is proposed and experimentally verified. This mechanism takes into account the difference in the work functions of the alloy components in the heating — melting — evaporation cycle and makes it possible to take into account...

The dynamics of charge separation states has been numerically simulated in order to calculate the polarization (in the third order of the perturbation theory) and its evolution in a pulsed optical field. Time evolution of the rotational states of the ortho-D2O isomer with a nonzero magnetic momentum and mixed ortho/para-D2O states have been calcula...

West Spitsbergen fjords have been probed (on shipboard) by a compact Raman lidar (Wave Research Center, Prokhorov General Physics Institute, Russian Academy of Sciences), based on a pulsed diode-pumped Nd3+:YVO4 laser with frequency doubling, in August, 2011. The evolution of lidar signal spectra (Raman, fluorescence, and elastic scattering) when a...

The phase conjugation regime is experimentally implemented in a cell with a liquid (water, ethanol, carbon tetrachloride) at the four-wave mixing of counter-propagating beams of diode lasers. Intracavity enhancement of the conjugate wave and the wave of the coherent anti-Stokes Raman scattering (CARS) arising in the interaction of the conjugate wav...

A mechanism of non-stoichiometric laser ablation is proposed and experimentally verified for multicomponent alloys. The analysis of four-component bronze samples in various excitation modes and the recorded laser plasma spectra revealed that disproportion of plasma elements during laser evaporation arises from selective evaporation of components at...

Here, we study a low (less than 0.1 µg/ml) concentration aqueous suspension of single-wall carbon nanotubes (SWNTs) by Raman-induced Kerr effect spectroscopy (RIKES) in the spectral bands 0.1–10 and 100–250 cm−1. This method is capable of carrying out direct investigation of SWNT hydration layers. A comparison of RIKES spectra of SWNT aqueous suspe...

Distinctive optical properties of single-wall carbon nanotubes (SWNT) are highly sensitive to variations in the environment. Here, we have studied SWNT in aqueous suspensions at a low (less than 0.1 µg ml−1) concentration by four-wave mixing (FWM) spectroscopy in the spectral bands of 0.1 to 10 cm−1 (≈300 GHz) and 100 to 250 cm−1 (3 to 7.5 THz). We...

Stationary Brillouin scattering in an elastic medium with spatially inhomogeneous distribution of the interatomic interaction Stationary Brillouin scattering in an elastic medium with spatially inhomogeneous distribution of the interatomic interaction potential is considered in the one-dimensional approximation. Frequency dependence of the optical...

Mandelstam-Brillouin (MB) steady-state scattering in an elastic medium with a dense local zone inhomogeneity is considered in the 1D approximation. It is shown that for a certain size of inhomogeneity, the scattered radiation spectrum contains individual resonances whose frequencies depend on the elastic properties of microscopic inclusions. Experi...

Four-wave mixing (FWM) spectroscopy is used to detect the rotational resonances of H2O and H2O2 molecules in DNA and denatured DNA aqueous solutions in the range ±10 cm-1 with a spectral resolution of 3 GHz. It is found that the resonance contribution of the rotational transitions of these molecules increases significantly in solutions rather than...

It is established for the first time that the intensities of deformation and valence Raman scattering (RS) bands in water vary oppositely in the processes of degassing and crystallising. Water degassing shifts the centre of a valence OH band to higher frequencies by approximately 2 cm¹, which points to a reduced contribution of structural complexes...

It is established for the first time by Raman scattering of second-harmonic pulses of an Nd:YAG laser that there are molecular complexes with frequencies of 3600, 3450, and 3200 cm¹ (which are characteristic of dimers, tetramers, and ice-like hexamers observed in HO molecular beams) in water at temperatures of 13 - 99 deg. C. The frequency of the i...

We carried out a remote study of ship wakes by optical methods. Both Mie and Raman scattering signals and their evolution were simultaneously recorded by gated detector (intensified CCD). The Mie scattering signal was detectable within 1 min ⁡ after water disturbance by a high-speed boat. According to an approximation of experimental data, Raman si...

Rotational resonances of ortho and para spin isomers of the H2O molecule are observed in hexagonal ice using four-photon spectroscopy of coherent light scattering. It is experimentally shown that the resonant contribution to the four-photon scattering signal from para H2O spin isomers in ice is about half as large as that in the liquid phase.

Resonant responses of Mandelshtam-Brillouin scattering from longitudinal and transverse acoustic waves at frequencies of νLS = ±1.15 cm−1 and νTS = ±0.7 cm−1, respectively, and at frequency of νSS = νTS \( \sqrt 3 \) = ±0.43 cm−1 were detected in K8 optical glass at room temperature using four-photon spectroscopy. We attribute this effect to the in...