Michael Kovalev

Verified

Michael verified their affiliation via an institutional email.

Learn more

Verified

Michael verified their affiliation via an institutional email.

Learn more

• PhD
• Senior Researcher at Russian Academy of Sciences

The broadening of the spectral absorption range of crystalline silicon to the near-and mid-IR region is possible by doping it using ion implantation and subsequent annealing methods. Pulsed laser annealing makes it possible to eliminate ion-induced defects, recrystallization of the crystal structure, and activation of impurities. The crystal struct...

This paper introduces a novel approach to the design of multi-element planar solar concentrators, aimed at optimizing solar energy harvesting systems. The proposed methodology is based on the integration of identical unit cells, strategically arranged to enhance solar radiation capture efficiency and achieve high angular selectivity. Mathematical m...

The development of planar integrated systems using silicon as the main material for the near-infrared spectral region is an important area of research due to its favourable properties, such as high compatibility with existing CMOS semiconductor technology and economic efficiency. However, the indirect bandgap of silicon (Eg = 1.12 eV) poses difficu...

Расширение спектрального диапазона поглощения кристаллического кремния до ближней и средней инфракрасной области возможно посредством его легирования с помощью технологий ионной имплантации и последующего отжига. Импульсный лазерный отжиг позволяет провести устранение ионно-индуцированных дефектов, рекристаллизацию кристаллической структуры и актив...

1030-nm, 300-fs laser inscription of separate microvoxels in bulk PMMA was performed at different peak laser intensities I 0 and exposures N. The microvoxel arrays were characterized by optical microscopy regarding the feature morphology, photoluminescence and Raman microspectroscopy regarding their morphological (voxel length and diameter) and str...

Novel nitridation/nitrogen doping process for silicon (Si) surfaces was developed, performing plasma-mediated pulsed laser treatment of a Si wafer in a liquid-nitrogen environment. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to characterize surface microtopography and analyzed chemical composition (carbon ∼7–20 a...

A novel double-impurity doping process for silicon (Si) surfaces was developed, utilizing nanosecond-laser melting of an 11 nm thick gold (Au) top film and a Si wafer substrate in a laser plasma-activated liquid nitrogen (LN) environment. Scanning electron microscopy revealed a fluence- and exposure-independent surface micro-spike topography, while...

Hyperspectral imaging is currently under active development as a method for remote sensing, environmental monitoring and biomedical diagnostics. The development of hyperspectral sensors is aimed at their miniaturization and reducing the cost of components for the purpose of the widespread use of such devices on unmanned aerial vehicles and satellit...

Spectral range of crystalline silicon absorption could be extended to near- and even mid-infrared region by its hyperdoping via ion-implantation technology, requiring the following thermal annealing for removing ion-induced defects, recrystallizing the crystalline structure and activating the doping impurity. In this article, the crystalline struct...

Silicon’s band gap (1.12 eV) limits its near-infrared photon absorption. Silicon hyperdoping creates energy states within the band gap, enabling near-infrared radiation absorption. Ion implantation is an efficient method for hyperdoping, but radiation-induced defects compromise silicon crystallinity. Pulsed laser annealing mitigates induced defects...

Появление кремниевой фотоники за последние два десятилетия создало условия для того, чтобы кремний стал предпочтительной платформой для фотонной интеграции. В этом обзоре мы предлагаем наш взгляд на растущую область интегральной фотоники ближнего инфракрасного диапазона на кремнии и перспективные технологии обеспечения этого роста. Представлен комп...

Light-trapping micro- and nanostructures generated on various material surfaces have garnered significant interest in recent years due to their pivotal role in various scientific and technological applications. Direct laser writing has emerged as a prominent, versatile, and practical method for fabricating these structures. In this study, we employ...

The absorption of light in the near-infrared region of the electromagnetic spectrum by Au-hyperdoped Si has been observed. While silicon photodetectors in this range are currently being produced, their efficiency is low. Here, using the nanosecond and picosecond laser hyperdoping of thin amorphous Si films, their compositional (energy-dispersion X-...

Light-trapping structures formed on surfaces of various materials have attracted much attention in recent years due to their important role in many applications of science and technology. This article discusses various methods for manufacturing light-trapping “black” silicon, namely laser, chemical and hybrid chemical/laser ones. In addition to the...

An improved approach to the synthesis of holographic filters, which are achromatic computer-generated Fourier holograms, is demonstrated, taking into account the spatial and spectral characteristics of the light field. An experimental testing of the obtained filters was carried out based on the use of a holographic wavefront sensor operating on the...

Nowadays, wavefront sensors are widely used to control the shape of the wavefront and detect aberrations of the complex field amplitude in various fields of physics. However, almost all of the existing wavefront sensors work only with quasi-monochromatic radiation. Some of the methods and approaches applied to work with polychromatic radiation impo...

Direct laser writing/ultra-hyperdoping technology was harnessed to fabricate a universal CMOS-compatible Si-based broadband (UV-THz) n-p junction detector, with its spectral response controlled by external liquid helium-nitrogen cooling. Near-far IR (2-40 μm) temperature-dependent photoconductivity (PC) was revealed in a biased n-p junction, made o...

The ultrashort-laser photoexcitation and structural modification of buried atomistic optical impurity centers in crystalline diamonds are the key enabling processes in the fabrication of ultrasensitive robust spectroscopic probes of electrical, magnetic, stress, temperature fields, and single-photon nanophotonic devices, as well as in “stealth” lum...

The ultrafast interaction of tightly focused femtosecond laser pulses with bulk dielectric media in direct laser writing (inscription) regimes is known to proceed via complex multi-scale light, plasma and material modification nanopatterns, which are challenging for exploration owing to their mesoscopic, transient and buried character. In this stud...

The cumulative achievements in the fields of science and technology have allowed us to substantially approach the solution of the phase problem in optics. Among all phasometric methods, single-beam methods are the most promising, since they are more variable and versatile. Single-beam methods are based either on the analysis of the intensity distri...

Ferroelectric nanodomains were formed in bulk lithium niobate single crystals near nanostructured microtracks laser-inscribed by 1030-nm 0.3-ps ultrashort laser pulses at variable pulse energies in sub-and weakly filamentary laser nanopatterning regimes. The microtracks and related nanodomains were characterized by optical, scanning probe and confo...

The transport-of-intensity equation provides a new non-interferometric and non-iterative access to quantitative information about the phase of a light wave by measuring intensity distributions. This equation can be used to implement a simple and accurate spatial phase measurement for optical testing of spherical surfaces. The method requires only a...

We present a new approach for a surface characterization based on the TIE method combined with the SEM. Experimental verification is carried out on the example of characterization of a crater on the surface of monocrystalline silicon (111). The approach is universal and can be used for any opaque object. It improves the robustness and stability of...

Red-colored high-pressure, high-temperature synthesized (HPHT) diamond was exposed in its bulk in a number of patterns to millions of 0.3-ps, 515-nm laser pulses focused by a 0.25-NA micro-objective. The resulting arrays of bright micrometer-scale spots produced at variable laser exposure and pulse energy was characterized by optical transmission m...

Microscale filamentation of 0.25 NA-focused, linearly and circularly polarized 1030 nm and 515 nm ultrashort laser pulses of variable pulse widths in fused silica, fluorite, and natural and synthetic diamonds demonstrates the Raman–Kerr effect in the form of critical pulse power magnitudes, proportional to squared wavelength and inversely proportio...

A straightforward method based on a solution of the transport-of-intensity equation for laser beam quality M2 factor measurement is presented. Demonstrated experimental results prove that the approach is valid. Reconstruction of the other laser beam spatial parameters is presented, namely: radius, waist position, angular divergence, Rayleigh length...

A development of a method for measuring the refractive index of optical media based on the transport-of-intensity equation (TIE) is proposed. The method requires only a complementary metal-oxide semiconductor (CMOS) camera, which registers intensity distributions in several planes. The obtained intensity distributions are used to solve the TIE, kno...

Single-shot surface ablation of (001) and (111) oriented natural diamond plates was performed by tightly focused (numerical aperture NA = 0.65) 1030-nm 0.3-picosecond laser pulses with variable polarization azimuth. Surface craters were characterized by scanning electron microscopy in terms of characteristic ablation 1/e-radii and threshold fluence...

Laser inscription of form-birefringent nanograting layers inside fused silica by ultrashort (femto-picosecond) laser pulses at 515 nm was studied as a function of laser, average power and pulsewidth in terms of fabrication regimes. Retardance magnitudes were acquired for single birefringent layers inscribed at different laser parameters, enabling f...

The filamentation process inside of the bulk of type IIa synthetic diamond with known crystallographic orientation has been studied as a function of the polarization state of the ultrashort laser pulses with a duration of 300 fs and a wavelength of 515 nm. The transmittance of the sample was measured using a photodiode, while the micro-image of the...

A simple method for reconstructing the spatial parameters of a laser beam, based on the transport-of-intensity equation, is presented. Registration of cross-section intensity distributions in several planes was carried out using a single CMOS camera. The processing of the experimental measurements with the help of specialized software helped to rec...

Проведено исследование процесса филаментации внутри объема синтетического алмаза IIа-типа с известной кристаллографической ориентацией в зависимости от состояния поляризации ультракоротких лазерных импульсов длительностью 300 fs и длиной волны 515 nm. Коэффициент пропускания образца измерялся с помощью фотодиода, а микроизображение филамента регист...

The bulk mapping of natural diamond poses problems where it is required to characterize various defects and measure their optical properties in volume. The combination of photoluminescence spectroscopy methods and methods for detecting the state of polarization in the volume will expand the functionality for mapping natural and artificial diamonds....

Optically active defects in natural diamonds form specific spectral bands in the optical absorption and luminescence spectra and are called optical centers. Optical centers in the visible spectral range and their corresponding defects are called color centers. Spectral absorption and luminescence bands usually occupy several tens of nanometers in t...

Silicon p-n junction photoelement fabricated on a p-doped wafer by sulfur-based n-doping of its sub-micron thick surface layer, exhibits at liquid-helium temperatures impurity-based near-far IR (2–21 $\mathrm{\mu}$ m) photoconductivity spectra in the form of well-resolved separate bands of neutral and ionized atomic-like and cluster-like sulfur cen...

Inter-band photoexcitation in bulk natural and synthetic diamonds by tightly focused near-IR (1030 nm) ultrashort laser pulses of variable duration (0.3-6.3 ps) promotes characteristic UV photoluminescence A-band and phonon-mediated free-exciton recombination bands, respectively, with distinct phonon progressions. The photoluminescence yield in the...

The dependence of the threshold fluence for surface ablation of such crystalline materials as silicon and diamond (with orientations (001) and (111)) on the direction of linear polarization of ultrashort pulses of different duration (0.3-3.3 ps) with a wavelength of 515 nm has been studied for the first time. The obtained values of the ablation flu...

Micrometer-thick layers of Pseudomonas aeruginosa bacteria were prepared on fluorite substrates and scanned by focused mid-IR femtosecond laser radiation that was spectrally tuned to achieve the selective excitation of either the stretching C–H vibrations (3 μm), or stretching C = O, C–N vibrations (6 μm) of the amide groups in the bacteria. The en...

A correction to this paper has been published: 10.1140/epjd/s10053-021-00234-0

Впервые проведены исследования зависимости пороговой плотности энергии абляции поверхности таких кристаллических материалов, как кремний и алмаз (с ориентациями (001) и (111)) от направления линейной поляризации ультракоротких импульсов различной длительности (0.3–3.3 пс) с длиной волны 515 нм. Полученные значения пороговой плотности энергии абляци...

The article discusses the implementation of ultrafast broadband excitation of A-band luminescence of natural diamond by femtosecond-laser pulses with low-energy near-IR photons. Such regime provides A-band luminescence yield with the fourth-power nonlinearity at low laser intensities and second-power nonlinearity at higher laser intensities. These...

Ultrafast visible-range excitation in natural diamond produces UV-VIS A-band photoluminescence with marginal zero-phonon line and intense regular multi-peak optical-phonon progression. The A-band photoexcitation can occur via band-center, center-center and band-band transitions, being related to two-photon (center-terminated), or interband three-ph...

High-rate direct femtosecond (fs) laser writing is a well-established technology for fabricating various micro-optical elements in bulk dielectrics. In this technology, the “heat accumulation” effect, occurring during high-repetition rate (∼ 1 MHz) exposure in dielectrics by a fs laser, enables ultralow-energy micro-modification via cumulative heat...

In this paper, we report a study on Si nanopatterns, fabricated as a one-dimensional (1D) Si nanograting with a sub-wavelength (≈200 nm) period. Unpolarized light normally incident on the nanopatterned Si becomes partially polarized and chiral over the entire visible range of 380–740 nm. The degree and the state of polarization of light were measur...

Recently the transport-of-intensity equation as a phase imaging method turned out as an effective microscopy method that does not require the use of high-resolution optical systems and a priori information about the object. In this paper we propose a mathematical model that adapts the transport-of-intensity equation for the purpose of wavefront sen...

Ultrafast heating of photoionized free electrons by high-numerical-aperture (0.25–0.65) focused visible-range ultrashort laser pulses provides their resonant impact trapping into intra-gap electronic states of point defect centers in a natural IaA/B diamond with a high concentration of poorly aggregated nitrogen impurity atoms. This excites fine-st...

Исследованы спектры пропускания фемтосекундных лазерных импульсов среднего ИК-диапазона (5-6.6 мкм) субмонослоем бактерий Staphylococcus aureus и Pseudomonas aeruginosa на кремниевой подложке в области характеристических полос поглощения белков и липидов, а также стационарные спектры после облучения. При облучении обнаружено обратимое "просветление...

The transmission spectra of femtosecond laser pulses in the mid-IR range (5–6.6 μm) were investigated of submonolayer of Staphylococcus aureus and Pseudomonas aeruginosa bacteria on a silicon plate in the region of characteristic absorption bands of proteins and lipids, as well as stationary spectra after irradiation. Invertible “translucence” of s...

A holographic wavefront sensor based on echelette grating model realized by a phase only SLM is presented. This scheme allows optical aberration measurement with high precision. The presented optical scheme and CGH synthesis algorithms were validated with simulations and experiments.

A scheme of a compact holographic wavefront sensor based on combination of computer-generated hologram and computer-generated Fresnel lens is presented. This scheme allows optical aberration measurement with high precision. The presented optical scheme is tested and compared to a scheme with physical Fourier lens. Since 2000, the direction of holog...

Multi-shot exposure of silicon surface in air by mid-infrared (MIR, 2.5–5 microns) femtosecond laser pulses results in an initial (Np = 2–5 shots) appearance of a bright spot with abnormally-oriented, bipolar shallow deeply-subwavelength ripples (period ∼ (0.2–0.4)λ, average trench ablation rate ∼ 10–20 nm/shot, trench depth < 100 nm), visualized b...

Ultrashort-pulse laser surface and bulk nano- and micromachining of dielectrics have multiple promising applications in micro-optics, microfluidics, and memory storage. The fundamental principles relate intrinsic inter-band multi-photon (MPA) and laser-induced intra-band free-carrier absorption (FCA) to particular ablation mechanisms and features....

This paper investigated the diffraction of a Gaussian laser beam on a binary mask and a refractive axicon. The principles of the formation of a zero-order Bessel beam with sharp drops of the axial field intensity edges were discussed. A laser optical system based on an axicon for the formation of a Bessel beam with quasi-uniform distribution of axi...

The action of ultrashort laser pulses on dielectrics leads to the processes of redistribution of the laser pulse energy in the interaction region. The mechanisms of ultrafast energy deposition and the electron dynamics under the action of ultrashort laser pulses determine the type of final structures or elements in the transparent dielectrics. One...

In this work, microscale holes and intermediate self-organized structures were obtained on the surface of a thin 50-nm silver film in air and under a water layer using single tightly focused femtosecond laser pulses with variable energy. We study the differences in the relief of microholes using scanning electron microscopy. The comparison of the s...

In various fields of photonics, there is a tendency to pass from elements of physical optics to elements of flat optics, primarily, due to a decrease in the dimensions of instruments and devices. Most frequently , spatial light modulators are used to efficiently and immediately simulate flat phase elements. In this work, we investigate the possibil...

All of the existing holographic wavefront sensors are either bulky or have low accuracy of measuring wavefront aberrations. In this paper, we present an improvement of the holographic method of measuring wavefront aberrations using computer-generated Fourier holograms. The novelty of this work lies in the proposed approach to the synthesis of Fouri...

In this work, the formfactor influence on the diffraction efficiency of 2D and 3D phase holograms was analyzed. Experimental results showed that holograms recorded in a chalcogenide glassy semiconductor and an azopolymer have limitations on maximum achievable diffraction efficiency. The coefficient of optimal exposure increase that is necessary to...

In interferential linear displacement sensors, accurate information about the position of the reading head is calculated out of a pair of quadrature (sine and cosine) signals. In double grating interference schemes, diffraction gratings combine the function of beam splitters and phase retardation devices. Specifically, the reference diffraction gra...

In various areas of photonics, there is a tendency to move from elements of physical optics to elements of flat optics, primarily due to reducing dimensions of instruments and devices. Usually, spatial light modulators are used to quickly output flat phase elements. In this paper, the possibility of replacing the optical system with a computer-gene...

Bulk microstructuring of silica glass was performed by one-dimensional raster-scanning of tightly focused visible-range femtosecond-laswer beam with different polarizations. Microstructures fabricated at linear and circular polarizations, demonstrated enhanced blue-range extinction without any distinct birefringence.

Reviewed the problems arising during the recording of holograms in bulk media, which manifest themselves in the first queue as the spatial resonance of the hologram recording field with refractive index inhomogeneities due to the already recorded part of the holographic lattice. And secondly, as a cross-interaction of two nonlinearities at recordin...

Optical sensors of linear displacements with diffraction gratings serving as the measurement scales are investigated. A method of stabilization of the phase difference of quadrature measurement signals, consisting in the use of an analyzing scale with a special structure, is proposed. A design of an optical encoder based on the method is proposed....

An algorithm that automatically calculates aberrations in the holographic wavefront sensor scheme previously proposed by the authors is described, which enables measuring aberrations by means of iterative generation of holograms on a phase spatial light modulator (SLM). The practical implementation of this algorithm on the basis of the feedback of...

Data encryption is becoming increasingly relevant with the development of digital technologies. A particularly promising direction is the development of encryption methods based on optical transformations. Fractional Fourier Transform is a well-known method of encoding data, especially graphic. However, an assessment of the method’s resistance to u...

An algorithm that automatically calculates aberrations in the holographic wavefront sensor scheme previously proposed by the authors is described, which enables measuring aberrations by means of iterative generation of holograms on a phase spatial light modulator (SLM). The practical implementation of this algorithm on the basis of the feedback of...

Phase shifts of light in orders of diffraction grating for the interference linear displacement sensor are considered. Using the phase diffraction grating with given geometric parameters of the surface relief allows one to stabilize phase relations in optical signals and in resulting signals outputted from the displacement sensor. Based on the math...

This paper discusses features of the phenomena that occur during plasma-chemical etching of optical glass when deep relief is being fabricated on high-precision components of devices, using apparatus with inductively coupled plasma.

The present article is dedicated to the problem of computer-generated holograms application for measurement of optical wavefront curvature with high precision. A holographic wavefront sensor scheme based on a phase-only spatial light modulator, which is used for CGH displaying, is proposed. The presented optical scheme and processing algorithm are...

An optical position encoder uses two difraction gratings in a measurement scale and measuring head for generating cosine measurment signals. This report is about special subperiod structuring of thees gratings for generating of two signals with quadrature phase shift for better the resolution of an optical position encoder.