L. A. Golovan’

• Dr. Sc.
• Professor at Lomonosov Moscow State University

New azochromophores (ACh) with terminal nitrile group have been synthesized. All compounds are crystalline at room temperature. Their melting points were measured by differential scanning calorimetry. The AСh containing carboxyl group have very high melting points. In this respect, carboxyl-free derivatives were preferred as azochromophoric additiv...

In this paper, we studied nonlinear absorption of infrared (IR) (1250 nm) femtosecond pulses and visible photoluminescence (PL) excited by them in liquid-crystal (LC) polymer films with embedded CdSe/ZnS core-shell type quantum dots (QDs). The dependence of nonlinear transmission on incident intensity indicated three-photon absorption in the films,...

Abstract: Chalcogenide vitreous semiconductors (ChVSs) find application in rewritable optical memory storage and optically switchable infrared photonic devices due to the possibility of fast and reversible phase transitions, as well as high refractive index and transmission in the near-and mid-infrared spectral range. Formed on such materials, lase...

Femtosecond laser-modified amorphous silicon (a-Si) films with optical and electrical anisotropy have perspective polarization-sensitive applications in optics, photovoltaics, and sensors. We demonstrate the formation of one-dimensional femtosecond laser-induced periodic surface structures (LIPSS) on the surface of phosphorus- (n-a-Si) and boron-do...

Ge2Sb2Te5 (GST225) looks to be a promising material for rewritable memory devices due to its relatively easy processing and high optical and electrophysical contrast for the crystalline and amorphous phases. In the present work, we combined the possibilities of crystallization and anisotropic structures fabrication using femtosecond laser treatment...

The possibility of manufacturing silicon nanoparticles by picosecond laser fragmentation of silicon microparticles in water is analysed. It is shown that for fragmentation duration of 40 min, the dependence of the average sizes of particles on the initial mass concentration of the micropowder varied in the range of 0.5 – 12 mg mL ⁻¹ is nonmonotonic...

Biodegradable and low-toxic silicon nanoparticles (SiNPs) have potential in different biomedical applications. Previous experimental studies revealed the efficiency of some types of SiNPs in tumor hyperthermia. To analyse the feasibility of employing SiNPs produced by the laser ablation of silicon nanowire arrays in water and ethanol as agents for...

In this Letter, we report on the circular anisotropy of third-harmonic (TH) generation in an array of silicon nanowires (SiNWs) of approximately 100 nm in diameter tilted to the crystalline silicon substrate at an angle of 45°. Numerical simulations of the scattering at the fundamental and TH frequencies of circularly polarized light by a single Si...

The efficiency of using silicon nanoparticles, produced by laser ablation of porous silicon in liquids, as agents for hyperthermia of tumours using laser radiation with wavelengths of 633 and 800 nm is evaluated. Using the optical parameters of the nanoparticles suspensions determined earlier by the spectrophotometry measurements, the heating of tu...

The feasibility of photohyperthermia treatment of nodular basal cell carcinoma (BCC) in presence of silicon nanoparticles is studied by numerical simulations employing Monte-Carlo and finite element methods.

One-dimensional periodic surface structures were formed by femtosecond laser irradiation of amorphous hydrogenated silicon (a-Si:H) films. The a-Si:H laser processing conditions influence on the periodic relief formation as well as correlation of irradiated surfaces structural properties with their electrophysical properties were investigated. The...

The influence of the structure of the polymer matrix on the main photoluminescence characteristics of composites based on core (CdSe) and core–shell type (CdSe/ZnS) quantum dots embedded in liquidcrystalline and amorphous polymers of similar chemical structure is studied. The photoluminescence spectra consist of two bands (2.15 and 1.70 eV), the fi...

Phase transitions and periodic surface modification in amorphous Ge 2 Sb 2 Te 5 thin films on multilayer substrate were revealed as a result of the samples irradiation by femtosecond laser pulses with the wavelength of 1250 nm. Raman spectroscopy revealed partial crystallization in the treated samples. Calculations and analysis of scanning electron...

A novel two-stage technique to fabricate silicon nanoparticles is reported. At the first stage, silicon nanowire arrays are formed by metal-assisted chemical etching. At the second stage, the nanoparticles are produced by pulsed laser ablation of the silicon nanowire targets in water and ethanol. The fabricated particles have relatively small mean...

In this work the optical properties of carbidized silicon nanowires (SiNW) are investigated.

Modern trends in optical bioimaging require novel nanoproducts combining high image contrast with efficient treatment capabilities. Silicon nanoparticles are a wide class of nanoobjects with tunable optical properties, which has potential as contrasting agents for fluorescence imaging and optical coherence tomography. In this paper we report on dev...

The paper discusses the possibility of manufacturing silicon nanoparticles, which are suitable for contrasting biological tissues imaged by optical coherence tomography, by femtosecond laser ablation of porous silicon in various liquids. The manufactured nanoparticles are characterised by average sizes of 87, 112, and 102 nm for cases of ablation i...

Sequential use of electrochemical etching and picosecond laser ablation in ethanol and liquid nitrogen allows fabrication of silicon particles with size smaller than 100 nm and high level of crystallinity. Fabricated ensembles of nanoparticles exhibit effective photoluminescence with emission peaks located within biotissue optical transparency wind...

We report on developing a technique for fabricating silicon nanoparticles by laser ablation of porous silicon and silicon nanowires in liquids that have potential for image contrasting in fluorescence imaging and optical coherence tomography.

We report on effects of the matrix on photoluminescence spectra and lifetime and efficiency of up-conversion of core-type CdSe and core/shell CdSe/ZnS quantum dots embedded into smectic and amorphous polymers.

Numerical simulations indicate difference in scattering of left- and right-handed circularly polarized waves in an array of silicon nanowires. Experiment demonstrates that such a structure despite its strong scattering possesses chiral cubic response.

Silicon nanoparticles with sizes of 50–300 nm have been formed via picosecond laser ablation of porous silicon and silicon microparticles in water using various targets. Raman spectroscopy has revealed the presence of a low amount of the amorphous phase in the obtained particles (10–12%) prepared from micro- and mesoporous silicon layers and almost...

Study of nanocomposites based quantum dots (QD) is of great importance for fabrication of novel media for radiation generation and control. Employment of liquid-crystal polymers (LCP) as a matrix for the QD embedding is very promising since they allow formation of ordered QD arrays and high QD concentration. Measurement of QD-LCP nanocomposite phot...

Measurements of the photoluminescent spectra and kinetics, and of the excitation spectra of photoluminescence of CdSe nanoparticles embedded in various polymer matrices, show that using a liquid crystalline polymer as a matrix makes it possible to increase the lifetime of photoluminescence and the quantum yield of this process.

Semiconductor quantum dots-particles with 3D restriction of the carrier movement-are subject of vaious studies since they open up possibilities to produce novel materials. The idea to form QD-based nanocomposite media for laser generation is of extreme attraction. In particular, this can be done with the help of II-VI QD (i.e. CdSe) and polymer. Em...

In this chapter, the nonlinear-optical properties of porous silicon and poroussilicon- based structures are discussed in close connection with their linear optical properties. Variations of the nonlinear susceptibility tensor for porous silicon in comparison with bulk silicon are discussed with special interest to the effect of optical anisotropy c...

Arrays of silicon nanowires (SiNWs) of about 100 nm in diameter formed by metal-assisted chemical etching of crystalline silicon (c-Si) substrates were studied regarding efficiency of optical interactions in them. Strong scattering in the SiNW arrays results in enhanced photon lifetime in them, which was evidenced by measurement of the cross-correl...

The efficiency of light scattering by nanoparticles formed using the method of picosecond laser ablation of silicon in water and by nanoparticles of mechanically grinded mesoporous silicon is compared. The ensembles of particles of both types possess the scattering coefficients sufficient to use them as contrast agents in optical coherence tomograp...

In this paper, we report on the effect of buffer gas on silicon nanoparticle formation in femtosecond laser ablation process. For the first time the nonmonotonic dependence of the silicon nanoparticle sizes on the gas pressure is obtained. Distributions of the particles on the size received by means of atomic-force microscopy indicate reducing the...

Silicon nanowire (SiNW) arrays formed by metal-assisted chemical etching of boron low-doped crystalline silicon (c-Si) substrates were studied regarding enhanced efficiency of optical interactions in them. Along with high diffuse reflection of the structures under study, Raman and third-harmonic signals exhibited an order of magnitude growth compar...

Light propagation in silicon nanowire layers is studied via Raman scattering, third-harmonic generation and cross-correlation function measurements. The studied silicon nanowire arrays are characterized by a wire diameter of 50-100 nm and a layer thickness ranging from 0.2-16 μm. These structures are mesoscopic for light in the visible and near inf...

The dependence of the linear and nonlinear optical properties of silicon nanowires (SiNWs) on their structural properties was investigated. SiNWs with diameter between 40 and 200 nm were grown on crystalline silicon (c-Si) substrates by metal-assisted chemical etching and had a strong scattering of light in the visible and infrared spectral range....

Raman scattering and second-harmonic generation processes in porous layers obtained by the electrochemical etching of polycrystalline silicon carbide, which contain nanocrystals with dimensions from several to hundreds of nanometers, have been studied. It has been found that the efficiencies of Raman scattering and second-harmonic generation in lay...

The photoluminescence (PL) of CdSe quantum dots (QDs) that form stable nanocomposites with polymer liquid crystals (LCs) as smectic C hydrogen-bonded homopolymers from a family of poly[4-(n-acryloyloxyalkyloxy)benzoic acids] is reported. The matrix that results from the combination of these units with methoxyphenyl benzoate and cholesterol-containi...

FIELD: instrumentation. NOVELTY - The sensing element is made in the form of a silicon structure, which has a wall thickness and clearance width selected from the interval of values from 0-5-50 microns, and the depth of slots from 10 to 200 microns. The silicon structure has porous nano-structure layer on the surface of walls. The porous nano-struc...

Random lasers are a developing class of light sources that utilize a highly disordered gain medium as opposed to a conventional optical cavity. Although traditional random lasers often have a relatively broad emission spectrum, a random laser that utilizes vibration transitions via Raman scattering allows for an extremely narrow bandwidth, on the o...

Broadband second-harmonic (SH) and sum-frequency generation was studied in KH2PO4 crystals with incorporated anatase modification of titania nanocrystals. A tiny amount (10−5 wt.%) of titania nanoparticles in the anatase phase exhibits a pronounced (up to 15%) increase of the SH efficiency in comparison with the nominally pure potassium dihydrogen...

Nanocomposite films containing nanocrystals of silicon and silicon carbide are fabricated by direct ion-beam deposition onto silicon substrates. The films obtained are by Raman spectroscopy and the photoluminescence method. It is found that the samples under study exhibit two photoluminescence bands, in the “red” and near-infrared (IR) (600–1000 nm...

This paper discusses the experimental results of a study of the polariton mechanism of the microstructuring of silicon in the near-IR region when it is irradiated with picosecond laser pulses. The results are presented of a numerical model analysis of the excitation conditions of surface polaritons in a semiconductor when it is irradiated by a sing...

The results of the study of the polariton mechanism of microstructuring of silicon in near-IR range during irradiation by picosecond laser pulses are presented to discussion. The experimental results of influence of laser pulses (1064 nm, 33 ps) on silicon in the dependence of laser energy, focusing conditions and number of pulses, as well as numer...

In this letter, we report on stimulated Raman amplification in YVO4 pumped by MHz repetition-rate picosecond pulses. We demonstrate that in the case of a tight focusing geometry the efficiency of this amplification is independent of the direction of the pump pulse propagation with respect to that of the seed pulse. The polarization properties of Ra...

We discuss supercontinuum generation in crystalline potassium dihydrogen phosphate matrix with incorporated TiO2 nanocrystals in the field of femtosecond laser pulses. The observed efficiency enhancement to be five times more comparing with the nominally pure KDP crystal.

Propagation of light in a highly scattering medium is among the most fascinating optical effect that everyone experiences on an everyday basis and possesses a number of fundamental problems which have yet to be solved. Conventional wisdom suggests that non-linear effects do not play a significant role because the diffusive nature of scattering acts...

Supercontinuum generation in crystalline potassium dihydrogen phosphate matrix with incorporated TiO2 nanocrystals in the field of femtosecond laser pulses is discussed. The efficiency enhancement is observed to be five times more comparing with the nominally pure KDP crystal.

We explore the feasibility of generating strong coherent anti-Stokes Raman scattering (CARS) signal in the backward direction.

We studied features of Raman scattering in silicon nanowire (SiNW) layers of 50−350 nm in diameter formed by means of chemical etching of crystalline silicon (c-Si) wafers with preliminary deposited silver nanoparticles in hydrofluoric acid. The c-Si wafers of differnt crystallographic orientations and doping levels were used, which results in vari...

In the present review, we consider in detail nonlinear-optical properties of porous silicon. The nonlinear-optical properties of porous silicon are discussed in close connection with its linear optical properties. Such coherent nonlinear-optical processes as the second- and third harmonic generation are considered, with special interest to the vari...

Silicon nanoparticles have been formed as a result of the irradiation of single-crystal silicon targets in distilled water and liquid nitrogen, by, respectively, picosecond and femtosecond laser pulses. The main structural properties of these nanoparticles have been investigated by atomic force microscopy, transmission electron microscopy, electron...

We studied features of Raman scattering and the third-harmonic generation in silicon nanowire (SiNW) ensembles formed by means of chemical etching of crystalline silicon (c-Si) wafers with preliminary deposited silver nanoparticles in hydrofluoric acid. The c-Si wafers of different crystallographic orientations and doping levels were used, which re...

We study the structure and optical properties of arrays of silicon nanowires (SiNWs) with a mean diameter of approximately 100 nm and length of about 1--25 mum formed on crystalline silicon (c-Si) substrates by using metal-assisted chemical etching in hydrofluoric acid solutions. In the middle infrared spectral region, the reflectance and transmitt...

We shall present the properties of "Littrow modes" in broad periodic waveguides that we recently demonstrated in SoI samples. In the band picture they correspond to multimode slow light. In the resonator picture, they mainly behave as Fabry-Perot resonators. However, there are several subtleties in their quasi-optics behaviour that we will discuss,...

Among open resonators of mesoscopic size, we have shown recently that broad waveguides with Littrow diffraction at one of their boundaries could produce a set of sharp resonances in a silicon-on-insulator implementation at 1550 nm. We draw here two perspectives: firstly, we make use of a fundamental theory initially proposed in 1995 by Demkov and O...

In this letter, we, for the first time, report on coherent anti-Stokes Raman scattering (CARS) spectroscopy of an ensemble of silicon nanowires (SiNWs) formed by wet chemical etching of crystalline silicon with a mask of silver nanoparticles. The fabricated SiNWs have diameter ranged from 30 to 200 nm and demonstrate both visible and infrared photo...

For the first time, we demonstrate traveling wave stimulated Raman scattering, which allows arbitrary direction of the generated signal towards the target.

Arrays of silicon (Si) nanowires with mean diameters of about 50-100 nm formed by wet-chemical etching of crystalline silicon wafers with low and high doping levels were investigated by means of photoluminescence and Raman spectroscopy. The photoluminescence bands in the spectral ranges of 650-900 nm and about 1100 nm were detected and explained by...

The self-action of light in birefringent mesoporous silicon films is studied using picosecond laser pulses. Two mechanisms of self-action of light in mesoporous silicon are found. One of them manifests itself at laser intensities below 3 MW cm-2 and tends to saturation. The other dominates at intensities above 10 MW cm-2. The former is related to t...

The method for the formation of silicon nanoparticles by picosecond laser pulses is studied upon the surface irradiation of the single-crystal silicon in various liquids. The ablation products are investigated using the atomic-force microscopy and Raman spectroscopy. The experimental results indicate the crystal-line structure of nanoparticles and...

The luminescence of the CdTe quantum dots deposited on glass substrate and introduced into the porous silicon oxide matrix is investigated. The experimental results on the photoluminescence with one- and two-photon excitation and cathodoluminescence indicate that the quantum dots introduced into the matrix retain the luminescence properties. The co...

This paper discusses the dynamics of nanoparticle formation during the pulsed picosecond laser ablation of samples of crystalline and porous silicon by means of elastic light scattering. Experimental measurements are presented of how the signal produced by scattering at the ablation products depends on the distance between the probe radiation and t...

he effect of light localization in photoluminescence (PL) and Raman scattering (RS) in silicon nanowires with diameter of 100 nm was investigated. The optical excitation was done by CW radiation of a YAG:Nd laser at 1.064 μm. The PL an RS intensities were found to increase strongly for the samples with Si nanowires in comparison with corresponding...

Photonic crystal as the porous silicon multilayer structure was designed and formed. Such structures can be characterized by increased nonlinear optical response due to the weak light localization and could be used to implement all-optical switching. We showed the possibility of the essential photonic band gap edge shift due to a shift of the photo...

The possibility to produce silicon nanoparticles by the method of the pulse laser ablation of monocrystaline silicon targets in the water, glycerol and liquid nitrogen have been shown. Studies by the atomic-force microscopy and Raman scattering methods revealed the nanoparticles have a crystalline structure and their mean size depends on the buffer...

It is demonstrated that intense photoexcitation of the surface of a semiconductor with femtosecond laser pulses can induce fundamental changes in its optical response and ensure conditions for the generation of surface electromagnetic waves of various types. The connection between electronic processes initiated in the surface layer by photoexcitati...

This study demonstrates the formation of silicon nanocrystals via laser ablation using a 1064 nm picosecond Nd:YAG laser in liquid media (water, glycerol, and liquid nitrogen). Atomic force microscopy is used to determine the particle size distribution. A 520.5 cm-1 line in the Raman spectroscopy is revealed which is an evidence of the crystalline...

The mode-locked Nd:YAG laser radiation (1.064 mum, 40 ps) transmitted through the samples was employed to study the two-photon absorption and nonlinear refraction of porous silicon. The mesoporous Si sample demonstrates self-focusing. The nonlinear refraction at low laser intensities and two-photon absorption at high laser intensities are sensitive...

Photonic crystals remain one of the most actively discussed topics of the modern optics. In particular, they are very promising for the control of such nonlinear-optical processes as harmonic generation and light self-action as well as for sensor applications. Thus, features of the phase matching effect on the nonlinear-optical process efficiency i...

The effective-medium model has been generalized within the dipole approximation, with allowance for the shape anisotropy and dynamic depolarization of semiconductor nanoparticles. The calculations revealed nonmonotonic dependences for the birefringence and dichroism on the nanoparticle size. Comparison of the measured and calculated refractive inde...

Multiple enhancement of the Stokes Raman scattering in grooved silicon structures, which consist of sequences of voids (grooves) and crystalline Si walls, was observed under excitation with wavelength close to the Si wall width of ∼1 μm. The results obtained are interpreted as a manifestation of the partial light localization within the grooved str...

It is shown by atomic force microscopy that nanoparticles formed upon ablation of surface of single-crystal and porous silicon by femtosecond laser pulses have a lateral size from several tens to 200 nm and a height from 2 to 30 nm. Dependences of the nanoparticle sizes and surface concentrations on the residual pressure, which demonstrate the gas...

In experiments on nonlinear-optical transmission of picosecond laser pulses at the wavelength of 1.064 μm threeorder-of-magnitude enhancement of the photoinduced absorption in optically anisotropic mesoporous silicon films compared to crystalline silicon (c-Si) was found. The effect is not sensitive to the polarization of the laser radiation and it...

Polarization-dependent structures have been formed on the silicon surface under the action of femtosecond laser pulses. Some model concepts are proposed to describe changes in the response of the semiconductor surface caused by the generation of a nonequilibrium electron-hole plasma and explain the excitation of surface polaritons and waveguide mod...

Polarization-dependent ripples were formed at silicon surfaces under femtosecond laser irradiation. Proposed theoretical model describes changes in optical response of semiconductor surface, induced by generation of nonequilibrium electron-hole plasma, and explains mechanism of surface polaritons and waveguide modes exciatation during femtosecond l...

The influence of the structure of holey-fibre cladding on the effective waveguide mode area and the spectral broadening of femtosecond pulses of titanium-sapphire and forsterite lasers is experimentally studied. These experiments demonstrate that the increase in the air-filling fraction of the holey-fibre cladding may substantially enhance the spec...

Periodic microstructures — ripples oriented perpendicular to the direction of radiation polarisation are produced by irradiating crystalline silicon with the (100) orientation of the surface by femtosecond laser pulses. The behaviour of the third-harmonic signal is studied in these microstructures. It is shown that the orientation dependences of th...

The refractive indices and the coefficients of optical absorption by free charge carriers and local vibrations in porous silicon (por-Si) films, comprising nanometer-sized silicon residues (nanocrystals) separated by nanometer-sized pores (nanopores) formed in the course of electrochemical etching of the initial single crystal silicon, have been st...

Nanoparticles were formed on the surface of single-crystal silicon as a result of irradiation of this surface with femtosecond laser pulses. According to the data of the atomic-force microscopy, the height of these nanoparticles ranges from 2 to 30 nm and their transverse size varies from 70 to 200 nm.

The Raman effect in grooved silicon structures consisting of an array of cavities (grooves) and silicon layers is studied. It is found that the intensity of the Stokes component increases severalfold when the thickness of the silicon layers (1–2 μm) is close to the excitation wavelength. The results obtained, interpreted as a manifestation of the e...

In this paper, a network of preferentially oriented pores in silicon oxide exhibiting the form anisotropy of optical and nonlinear optical properties is demonstrated. The oxidized porous silicon (OPS) birefringence is enough to compensate for the material dispersion of this material and achieve the phase-matched TH generation. The OPS form birefrin...

Birefringence of porous-silicon films prepared by electrochemical etching of boron-doped Si(110) wafers with a resistivity of 25–45 mΘ cm has been studied. The samples are found to exhibit the properties of a negative uniaxial crystal with the optical axis oriented along the [1 [`1]\bar 1 0] crystallographic direction. The possibility of using poro...

The phenomenon of optical anisotropy in porous semiconductors and dielectrics (porous silicon, gallium phosphide, and alumina) and photonic crystal structures formed on their basis is reviewed. It is shown that anisotropic nanostructuring of initially isotropic media leads to the occurrence of strong birefringence. Applicability of the effective-me...

We consider the optical properties of semiconductor - insulator and insulator - insulator nanocomposites, including porous materials such as silicon, gallium phosphide, aluminum oxide, and structures based on them. The main focus is on the effect of form birefringence, which is caused by the anisotropy of pores in the materials under study. The app...

This paper aims to study mesoporous silicon with diameter range of 10-100 nm. The mesoporous Si samples, obtained by electrochemical etching, exhibit negative birefringence. Transmission measurements show effective two-photon absorption and self-focusing which depends on the porosity of the samples.

This paper investigates the silicon surfaces structured by femtosecond laser pulses by the scanning electron microscopy (SEM), atomic-force microscopy (AFM), third-harmonic (TH) generation, photoluminescence (PL), and Raman spectroscopy techniques.