Mikhail V. Kochiev

Universität Kassel · INA

Different types of ultrafast radiative transitions are considered. The most interesting among them is the case when the radiative transition is accelerated by the configurational transformation of a structural unit where it occurs. Impurity-induced VUV excitation bands of doped Li2B4O7 are attributed to the creation of impurity-bound excitons. When...

A new method for preparing the males genitalia from the tribe Phycitini using the Slide Dryer BIS-N 209–1 is proposed. The recommended time interval for exposition in KOH solution is from 30 to 50 min with a fixed temperature of 80 °C. It is shown that the degree of light transmittance of the genitalia depends on time in an exponential way. The lig...

The egg chorion morphologies of Dahlica triquetrella (Hübner, 1813) and Dahlica lichenella (Linnaeus, 1761) are described. These two species well differ from each other by diameter of the micropyle, by number of micropyle pores, and by diameter of the micropyle rosette.

We study photoluminescence (PL) spectra and exciton dynamics of the MoS2 monolayer (ML) grown by the chemical vapor deposition technique. In addition to the usual direct A-exciton line, we observe a low-energy line of bound excitons dominating the PL spectra at low temperatures. This line shows unusually strong redshift with an increase in the temp...

We study photoluminescence (PL) spectra and exciton dynamics of MoS$_2$ monolayer (ML) grown by the chemical vapor deposition technique. In addition to the usual direct A-exciton line we observe a low-energy line of bound excitons dominating the PL spectra at low temperatures. This line shows unusually strong redshift with increase in the temperatu...

Sub-nanosecond luminescence of Mn²⁺ in Mn-, Sn/Mn-, and Cu/Mn-doped Li2B4O7 ceramics is observed under laser excitation. Picosecond pulsed laser radiation (350–370 nm) generates the frequency-doubled radiation directly in a single microcrystal selected in a ceramic sample, with this secondary radiation falling within the impurity-induced VUV excita...

The spectral and spatiotemporal dynamics of photoluminescence in monolayers of transition metal dichalcogenide WSe$_2$ obtained by mechanical exfoliation on a Si/SiO$_2$ substrate is studied over a wide range of temperatures and excitation powers. It is shown that the dynamics is nonexponential and, for times $t$ exceeding $\sim$50 ps after the exc...

The spectral and spatiotemporal dynamics of photoluminescence in monolayers of transition metal dichalcogenide WSe2 obtained by mechanical exfoliation on a Si/SiO2 substrate is studied over a wide range of temperatures and excitation powers. It is shown that the dynamics is nonexponential and, for times t exceeding ∼50 ps after the excitation pulse...

We study the spin dynamics in a high-mobility two-dimensional electron gas confined in a GaAs/AlGaAs quantum well. An unusual magnetic field dependence of the spin relaxation is found: as the magnetic field becomes stronger, the spin relaxation time first increases quadratically but then changes to a linear dependence, before it eventually becomes...

We study the spin dynamics in a high-mobility two-dimensional electron gas confined in a GaAs/AlGaAs quantum well. An unusual magnetic field dependence of the spin relaxation is found: As the magnetic field becomes stronger, the spin relaxation time first increases quadratically but then changes to a linear dependence before it eventually becomes o...

The low-temperature emission spectrum of CdSe colloidal nanoplatelets (NPLs) consists of two narrow lines. The high-energy line stems from the recombination of neutral excitons. The origin of the low-energy line is currently debated. We experimentally study the spectral shift, emission dynamics, and spin polarization of both lines at low temperatur...

We investigate the statistics of microcavity polariton Bose–Einstein condensation by measuring photoluminescence dynamics from a GaAs microcavity excited by single laser excitation pulses. We directly observe fluctuations (jitter) of the polariton condensation onset time and model them using a master equation for the occupancy probabilities. The ji...

Photoluminescence kinetics is measured for spatially direct and indirect excitons in CdTe quantum dots excited by second harmonic radiation pulses of a picosecond Ti: sapphire laser. The width of a ZnTe barrier layer varied in the range of 2 - 12 monolayers (MLs). Since the photoluminescence decay curves are not described by a single exponential de...

We study the band-edge exciton fine structure and in particular its bright-dark splitting in colloidal semiconductor nanocrystals by four different optical methods based on fluorescence line narrowing and time-resolved measurements at various temperatures down to 2 K. We demonstrate that all these methods provide consistent splitting values and dis...

The influence of gold nanoparticles deposited on the surface of a Si0.95Ge0.05/Si quantum-well heterostructure with a thin Si cap layer on the spectra of low-temperature recombination radiation of biexcitons and an electron–hole liquid confined in the quantum well is investigated. The spectra of both visible and near-infrared radiation are recorded...

A comprehensive experimental investigation of exciton and biexciton recombination in GaAs/AlGaAs quantum wells is presented. Exciton and biexciton recombination times are found to be 16 and 55 ps, respectively. A method of determining the dynamics of the exciton temperature is developed. It is shown that both exciton and biexciton recombination pro...

The kinetics of accumulation of long-lived excess holes that appear in GaAs/Al0.05Ga0.95As shallow quantum wells under above-barrier photoexcitation and their relaxation is studied by time-resolved photoluminescence spectroscopy. The establishment of a steady state in the nonequilibrium electron-hole system under various combinations of above-barri...

Photoluminescence kinetics in multiperiod GaAs/AlGaAs quantum-well structures with asymmetric barrier heights has been investigated. Owing to the barrier asymmetry, a time constant of nonradiative recombination between the laser subbands of 9 ps has been achieved, which is record long for unipolar lasers and exceeds the nonradiative relaxation time...

The dynamics of excitons and trions in GaAs/AlGaAs heterostructures with shallow quantum wells is studied in time-resolved photoluminescence experiments carried out with different repetition rates of picosecond pump pulses for the cases of intrawell, above-barrier, and“two-color” excitation. It is established that excess charge carriers of one type...

The effect of the excitation level on the dynamics of heavy-hole exciton photoluminescence in tunneling-isolated GaAs/Alx Ga1 − x As (x = 0.05) shallow quantum wells at temperatures of 5 to 70 K is investigated. It is shown that the exciton lifetimes depend strongly on the excitation level, while the activation energies characterizing the thermal e...

We assume that a coherent phonon generation was found out in structures with a single graphitized layer under picosecond laser excitation by means of the Pump/Probe method. The thermal component of the response was calculated that allowed us to define the photothermal coefficient of the graphitized layer as well as its thermal conductivity from the...