Vol 88, No 6 (2024)

We consider the problem of quantum metrology with simultaneous measurement of several phase parameters in the framework of current tendencies of development of alternative navigation. The fundamental limits of linear and nonlinear metrology are studied. The effect of losses on the accuracy of quantum metrology for several parameters is revealed. A realistic scenario for preparing three-mode NooN states using atomic bright solitons is proposed.

A theoretical study of the optical response of a two-dimensional supercrystal (monolayer) of quantum emitters with a doublet in the excited state to the action of a continuous external field has been carried out, considering the dephasing of the electronic states of the system. The secondary field acting on the V-emitter from other V-emitters of the system forms their nonlinearity and provides internal positive feedback, which leads to bistability, periodic and aperiodic auto-oscillations and including chaotic behavior. In the presence of dephasing, the multistability of the optical response is preserved. Phase relaxation leads to a change in the scenario of the system dynamics from chaos to periodic oscillations of the field amplitude, i. e., to a “chaos — limit cycle” bifurcation, a decrease in the reflectivity of the monolayer in linear and nonlinear modes.

A biophysical model has been proposed for the formation of the main types of radiation damage to DNA in mammalian and human cells under action of intense femtosecond pulses in the visible and near-IR ranges.

NaYF₄: Yb, Er particles were synthesized by hydrothermal method in the form of rods of 1.4 µm × 70 nm average size. Their surface was modified with L-cysteine, which provided hydrophilic properties. It was shown that the modified particles exhibit upconversion luminescence in the visible spectral range upon 980 nm laser excitation. Their temperature calibration in physiological solution was carried out. The possibility of remote temperature measurement in the biologically significant range of temperature (293—323 K) with an average sensitivity of 43 × 10^—4 K^—1 and an accuracy of ±1.0 K was shown. A demonstration experiment was performed on the living nervous system of the grape snail Helix lucorum. The nanosensors have been successfully used for bioimaging and remote low-invasive temperature measurement with a spatial resolution of 10 µm.

A modification of the Klyshko method for absolute calibration of analog photodetectors is considered. It is shown that the photocurrent distribution of an analog detector can be approximated by convolution of the Poisson distribution of the number of photoelectrons with a function describing single photopulses, while the number of photons incident on the detector can be determined from the statistical properties of biphoton radiation. The ratio of the number of photoelectrons to the number of photons gives the efficiency of an analog photodetector, which can be used for measuring the intensity of radiation incident on the detector in units of photon numbers.

A brief overview of the author’s theoretical research on localized optical autowaves is presented. One-dimensional autowaves accompanied by the formation of localized quasi-monochromatic and unipolar autosolitons at their fronts are considered. The lifetimes of such objects are on the order of the relaxation times of the populations of quantum levels of non-equilibrium media. The characteristic durations of autosolitons exceed the phase relaxation times.

The values of fluorescence quantum yield upon using by the procedures of relative and of absolute quantum yields were measured for a set of porphyrins and phthalocyanines with different activities of bands in the absorption spectrum. The correlations between of the values quantum yields and optical densities at the absorption bands of the samples has been estimated that provides an opportunity to estimate the nature of the internal filter effects.

We presented the results of study of lasing from molecular nitrogen ions in laser plasma produced by femtosecond radiation pulse. It is shown that the maximum intensities at the wavelengths of 391.4 and 427.8 nm are observed at nitrogen pressure of 30 and 500 mbar respectively. The radiation divergence is tens mrad and is close to geometric. When the focal length of lens changes from 15 to 40 cm the pulse duration at wavelength of 391.4 nm varies from 1.83 to 3.5 ps.

Water-soluble organic phosphors based on 3-(1,3-benzothiazol-2-yl)-4-hydroxybenzene sulphonic acid were first studied experimentally and by density functional theory. The phosphors have differences in chemical structure. For one of them there is a large Stokes shift that results from intramolecular proton transfer in the excited state.

We developed the frequency recovery method of laser pulses necessary for synchronizing quantum states transmitted from a satellite and registered at a ground station. Experimental modeling of a quantum key distribution session between a satellite and a ground station is also considered. The data obtained during the experiment were used to test the method of recovering the repetition frequency.

In the photoluminescence spectra of natural type Ia diamond crystals, a zero-phonon line with a position of 488.9 nm (2.53 eV) is observed. The excitation spectrum of the system is mirror to the emission spectrum. The 488.9 nm line has phonon repetitions corresponding to an energy of 0.073 eV. A change in temperature from 77 to 313 K shifts the position of the system by 1.01 nm toward the red region, and the decrease in intensity and broadening of full width at half maximum is non-linear. The characteristics of the electron-phonon interaction and distribution in the bulk of the crystals of a defect with a zero-phonon line of 488.9 nm are like the characteristics of defects of a nitrogen-vacancy nature.

We study of spectral characteristics of LiF-UO₂ crystals with radiation induced color centers and their stability under action of emission of blue light emitting diode. The luminescence band with bandwidth 500—750 nm was observed upon excitation by blue light emitting diode emission. This indicates the possibility of using LiF crystals, containing uranium and radiation induced color centers (F₂, F₃⁺), as a phosphor, that possesses high stability due to special radiation treatment, for white light sources.