The static and dynamic characteristics of waveguide photodetectors with an absorbing region based on InGaAs/GaAs quantum well-dots were studied at room temperature. The absorption band of InGaAs/GaAs quantum well-dots is in the spectral range from 900 to 1100 nm. The waveguide photodetectors have a width of 50 μm and a length of the absorbing region from 92 μm to 400 μm. A low dark current density (1.1 and 22 μA/cm 2 at -1 and -20 V) and cut off frequency of 5.6 GHz, limited by the time constant of a parasitic equivalent electric RC-circuit, were obtained. Keywords:waveguide photodetector, modulation frequency, quantum well-dots, integrated photonics.

The laser generation characteristics of microdisc lasers with optically coupled waveguide operating in continuous wave mode at elevated temperatures are investigated. Laser generation and waveguide effect at temperatures up to 92.5°C were demonstrated. The measured characteristic temperature of microlasers was 65 K in the range of 25–92.5°C.

We study the optical properties of InAs/GaAs(001) quantum dots (QDs) overgrown under different V/III flux ratios using photoluminescence (PL) and excitation spectroscopy. When the V/III flux ratio is low, a series of pronounced QD-related peaks is observed in the $77-\mathrm{K}$ PL spectrum over a $200-\mathrm{meV}$ broad spectral interval with the brightest one located at 1.37 eV. With increasing V/III flux ratio, the PL spectrum is red-shifted (to 1.16 eV) and then blue-shifted again (to 1.26 eV), while becoming smoother. We explain this behavior in terms of enhanced QD decomposition, the mechanism of which is different in cases of deficiency and excess of arsenic during the overgrowth.

We have studied superluminescent diodes with simplified design and active region based on 5 or 7 layers of InGaAs/GaAs quantum well-dots (QWDs). Emission peaks of the individual QWD layers are shifted with respect to each other by 15–35 nm to provide as wide as possible emission line in a superluminescent mode with central wavelength of about 1 μm without significant spectral dips. For superluminescent diodes with the active region based on 5 and 7 QWD layers, the maximal value of full width at half maximum of emission spectrum was 92 and 103 nm respectively.

One drawback of self-organized quantum dots is their low optical gain. The development of new shaping methods that would allow higher gain, for example, due to a higher surface density of the QD array, remains an important task to date. In the present work, arrays of quantum dots have been formed by substituting phosphorous atoms with arsenic ones in a thin InGaP epilayer. Based on transmission electron microscopy data, the surface density was estimated to be about 1.3 x 10(12) cm(-2), which is one of the highest values for quantum dots on GaAs. The influence of an additional InGaAs epilayer (quantum well) on the luminescence properties of quantum dots was investigated in a wide temperature range and different optical pumping levels. It was found that placing the quantum well under the layer of quantum dots has little effect on the central emission wavelength, while quantum dots covered with the InGaAs demonstrate a strong red shift of the luminescence spectrum. A transition from a nonequilibrium to an equilibrium distribution of charge carriers over quantum-dot states, related to the lateral transport of charge carriers over quantum dot array, similar to that previously observed in In(Ga)As Stranski-Krastanow quantum dots, was revealed. This is manifested in a change in temperature dependencies of the linewidth and peak position of the photoluminescence band. For the structures under study, this transition occurs at a temperature of about 125 K. Rapid thermal annealing of the structures allows to increase the integrated photoluminescence intensity of quantum dots up to 4 times, while the maximum of the spectrum remains almost unchanged, provided that the annealing temperature does not exceed 620 degrees C.

In this work, we investigate microlasers with InGaAs/GaAs quantum well-dots in the active region with broken rotational symmetry of the cavity. For the first time, lasing at elevated temperatures has been demonstrated for limaçon-and quadrupole-shaped injection microlasers. Deviation of the cavity shape from the circular leads to the directionality of the emission in the lateral direction. The quality factor of structures is estimated to be at least $10^{5}$. The minimum linewidth was found to be $\sim 200 \mathrm{MHz}$. The emitted power in the selected direction increases with increasing deformation parameter and achieves 3 times more than that of the symmetric microcavity in the range of 40 degrees.

The use of glass capillaries with an outer diameter at their sharp end of less than 0.3 μm as probes in a manipulator based on an atomic force microscope (AFM) operating in a dynamic full-contact mode is considered. Various aspects of setting up the feedback system in this mode of AFM operation were studied to correctly obtain an image of the topography of the sample under study. Examples are given of the use of capillaries as probes for moving nanowhiskers with a characteristic diameter of 100 nm and hexagonal boron nitride (hBN) flakes with characteristic sizes from units to hundreds of micrometers. The possibility of creating and moving liquid droplets with a volume of less than 100 attoliters has been demonstrated.

Heterostructure with InGaAs/GaAs quantum well-dots was investigated in temperature range 10-300 K using photoluminescence spectroscopy in CW mode as well with time resolution. Obtained decay times were splitted into radiative and nonradiative components of carrier lifetime. It is found that radiative lifetime demonstrates exponential growth with temperature rise, while temperature dependence of nonradiative one is much weaker. Keywords: semiconductors, quantum well-dots, photoluminescence, time resolution, lifetime, temperature dependence.

The temperature characteristics of ring lasers with a diameter of 480 μm of an original design with an active region based on 10 layers of InAs/InGaAs/GaAs quantum dots are studied. The lasers demonstrated a low threshold current density (200 A/cm2 at 20oC), the characteristic temperature of the threshold current in the range of 20-100oC was 68 K, the maximum lasing temperature was as high as 130oC. These values are only slightly inferior to the parameters of the edge-emitting lasers fabricated from the same epitaxial wafer. Keywords: semiconductor ring lasers, InAs/GaAs quantum dots, optical waveguide, temperature characteristics.

In this papaer, the emission characteristics of InAs/InGaAs quantum dot (QD) microdisk lasers, of different cavity diameters, with a top split electrical contact formed using the focused ion beam technique are investigated. The dependences of the threshold currents of two-state lasing (i.e. currents corresponding to the start of the ground- and excited-state lasing) for microdisks of 24 and 28 mu m diameters on the electrical contact area are presented. The contact area was found to influence the threshold currents of two-state lasing in microdisks. It is shown that a decrease in the area of the injected electrical contact leads to a decrease in the current corresponding to the start of the excited-state lasing, while the ground-state (GS) lasing threshold remains virtually unchanged. The temperature evolution of the threshold currents for two-state lasing was also studied in microdisks with different electrical contact areas. We demonstrate that the use of contacts of different areas is a method of controlling the threshold currents of two-state lasing and can be used in engineering of QD lasers intended, for example, for multi-level signal transmission with wavelength multiplexing by switching from the GS to excited-state lasing.

spectral dependencies of the electroluminescence intensity of a microdisk laser with a diameter of 31 μm with active region based on InAs/InGaAs quantum dots, operating in the continuous-wave regime, are investigated in a wide range of injection currents. Simultaneous lasing through the ground and excited states of quantum dots under intense excitation is demonstrated in injection microdisk laser for the first time. At low pumping powers lasing occurs via ground states of quantum dots only.

A model is proposed that makes it possible to analytically analyze the speed performance of a waveguide p-i-n photodiode with a light-absorbing region representing a multilayered array of quantum dots separated by undoped spacers. It is shown that there is an optimal number of layers of quantum dots, as well as an optimal thickness of the spacers, which provide the widest bandwidth. The possibility of achieving a frequency range (at the level of -3 dB) above 20 GHz for waveguide photodiodes based on InGaAs/GaAs quantum well-dots is shown Keywords: photodiode, quantum dots, speed.

— The review presents the experiments performed with the KEDR detector at the e^ + e^ - collider VEPP-4M in the energy range of √(s) = 1.84–3.88 GeV. The cross section of e^ + e^ - annihilation to hadrons was measured at 22 points of this range and the search for narrow resonances was conducted below 3.1 GeV. The masses of J / . -0emψ and ψ (2S) mesons were measured with a record accuracy better than 3 ×10^ - 6 ; their partial and total widths were determined. Measurements of the tau lepton mass and masses of charged and neutral D mesons were performed with high precision. The measurements of the ψ (3770) parameters are discussed, and attention is drawn to some inconsistency of the procedure employed by the Particle Data Group for determining its parameters.

The internal loss at the lasing threshold were studied experimentally and numerically in laser cavities comprising dense arrays of InGaAs/GaAs quantum dots (quantum well-dots) as a function of the number of their planes and the output loss. Numerical values of the parameters were found that determine the free-carrier absorption in the active region and in the waveguiding layer. The optimal design of the laser diode was determined to achieve the highest external differential efficiency.

The paper reports on the implementation of two-level lasing in injection micro -lasers with self-organized InAs/GaAs quantum dots. Emission bands related to the radiative electron-hole recombination involving ground and several excited states of quantum dots are observed in the spontaneous electroluminescence spectra. We investigated two-level lasing via the ground and first excited states of quantum dots in microdisks with different cavity diame-ters. A decrease in the threshold currents is observed for both ground and first excited transi-tions in quantum dots with a decrease in the microdisk diameter. The temperature dependences of the threshold current density for microdisks of various diameters suggest that two-level lasing is observed up to 90-100 & DEG;C.

In this work, we study the characteristics of semiconductor microlasers based on the heterostructure with two coupled waveguides intended to improve heat dissipation in cw regime. We analysed total output optical loss of the microlasers, their spectral characteristics, output power, emission pattern and thermal resistance. We observed that the use of the principle of two coupled resonant planar waveguides, active and passive, as well as p-side down bonding, significantly reduces the thermal resistance of microlasers and improves their performance.

In the present work, we study the possibility of the emission output of a semiconductor microring laser through a radially coupled optical waveguide. Room temperature lasing has been achieved in continuous wave regime with the wavelength of similar to 1090 nm. The characteristics of microlasers with and without waveguide have been compared. We have performed a spatial scanning with simultaneous detection of the laser radiation at an injection current above the threshold. We have observed an increase in the output power up to two times due to the use of a coupled waveguide.

For the first time we show time-resolved photoluminescence dependencies with 0.2 ps resolution for the novel type of InGaAs/GaAs quantum-sized heterostructures, referred to as quantum well-dots (QWDs). Photoluminescence upconversion method, that allows achieving time resolution up to 0.2 ps, was used to obtain time-resolved spectra for light (lh) and heavy hole (hh) optical transitions of QWDs. We concluded that the capture of charge carriers to the lh and hh states of QWDs occurs simultaneously in the time range of similar to 10 ps and is probably limited by carrier diffusion in the matrix. The characteristic time of photoluminescence decay for the hh state (3 ns) was found to be greater than that of lh one (2 ns).

We propose an approach for encoding and transmitting information based on the use of a quantum dot laser, which, depending on the injection current, emits either one of two or simultaneously two spectral components, with different wavelengths. When the laser is modulated by current, each lasing line is detected by an independent photodiode, and thus the information is encoded by both the intensity of each line and its wavelength.