Journal of Russian Laser Research最新文献

Many devices based on silicon and other photonic integrated circuit platforms exhibit significant polarization dependence. Polarization beam splitter (PBS) is a device that split optical signals into transverse electric (TE) and transverse magnetic (TM) modes. Among various PBSs, asymmetric directional couplers are widely used due to their fine performance, but their working bandwidth is limited due to wavelength changes that can lead to deviations in effective refractive index and coupling strength. We propose a PBS, which uses metamaterial anisotropy to replace structural asymmetry and break the bandwidth bottleneck. It achieves good performance in the wavelength range of 258 nm, where the extinction ratio of the TM polarization is greater than 24 dB and that of the TE polarization is greater than 26 dB. It covers the E, S, C, L, and U bands, and the coupling area is as small as 7.25×2.625 μm, with a total device footprint of 15.65×6.125 μm.

We present the results of our study of nonlinear optical response observed in plasmon–exciton nanostructures based on PbS quantum dots passivated with thioglycolic acid and gold nanorods under the influence of 10 ns second harmonic pulses (532 nm) of Nd³⁺:YAG laser. We show that the association of components of a hybrid nanostructure leads to increase in the reverse saturable absorption in PbS quantum dots against the background of nonlinear refraction. Coating quantum dots with a monolayer of SiO₂ reduces this effect due to blocking the process of phototransfer of charge from a quantum dot to a metal nanoparticle, which is confirmed by the quenching and reduction in the luminescence lifetime of PbS quantum dots in the presence of gold nanorods.

We asses impact of the temperature of ⁸⁷Rb atoms on the linewidths and amplitudes of the F = 1 → F′ = 0, 1, 2 and F = 2 → F′ = 1, 2, 3 hyperfine resonances of the ⁸⁷Rb D₂ line, using the circularly-polarized pumping beam and the probe laser beam. To achieve high-precision and accuracy, frequency-stabilized narrow-linewidth extended-cavity diode lasers, we employ a temperature-controlled Fabry–Pérot interferometer and a magnetically-shielded temperature-controlled Rb cell with dimensions in the centimeter range, containing enriched ⁸⁷Rb atoms. Consequently, the linewidth and amplitude measurements are conducted with inaccuracies of 1.5 MHz and 0.4 mV, respectively.

Rydberg atom has a very large polarizability proportional to n⁷ (n is the principal quantum number), the energy interval between adjacent energy levels is in the microwave frequency band, and the transition between adjacent energy levels has a huge dipole moment proportional to n⁴; as a result, the Rydberg atom is extremely sensitive to the external field, making it an important means of microwave detection. The interaction of Rydberg atoms with laser fields can be described within the framework of density matrix theory. In this paper, based on a four-level system with multiple laser fields, we study the relationship between the population distribution of different energy levels and the detuning of the coupling field, as well as the effect of the Rabi frequency of microwave field on the electromagnetically induced transparency (EIT) signal by solving the density matrix of the steady state system. Considering the characteristics of density matrix, we assume that the diagonal elements are real and the off-diagonal elements are complex. We find that the operation efficiency of this construction method is twice as high as that of the direct representation by complex numbers. At the same time, we obtain that the Rabi frequency of microwave electric field is proportional to the splitting of EIT signal within a certain range.

We investigate effects of a classical external field and the initial state of the field on the nonlinear interaction of a Λ-type three-level atom with the two-mode field through the Raman type interaction. Appropriate canonical transforms are performed for atomic states. The analytic solution to the model is obtained, using the Schrödinger differential equation. The wave function is obtained under specific initial conditions of the atom and field. The effect of a classical external field and the initial state of the field on the population occupations, the squeezing phenomenon, and the atomic emission spectrum are studied. The collapse–revival phenomena are affected by the presence of the classical field. Increasing the activation of the role of the initial state of the field improves the phenomena of collapses and revivals. The squeezing intervals decrease with increase in the classical field effect. The squeezing intervals increase with decrease of the parameter of the initial state of the field. The maximum values of the emission spectrum are improved after taking into account the classical field. In addition, the peaks significantly decrease after reducing the influence of both the bandwidth of the filter and the interaction time.

For CdZnTe crystals containing extended defects – coherent and incoherent twin boundaries, as well as lamellar systems of twins, we measure the propagation patterns of surface acoustic waves (SAW) in the gigahertz range excited by a sharply focused femtosecond laser pulse. Comparison of the calculated SAW radial velocities with experimental data allows us to determine the local crystallographic orientation of crystal regions with defects. We discover strong anisotropic scattering of SAW at twin boundaries and show that the structure of the twin boundary can be determined from the pattern of SAW scattering. Also, we demonstrate the non-reciprocal SAW propagation in lamellar twin systems, as well as quasi-waveguide SAW propagation along the lamellar twin layer.

We determine the evolving probability representations of several important nonclassical states of the inverted oscillator by applying the method of integrals of motion for this system. The considered nonclassical states initially prepared in the potential of the harmonic oscillator are even and odd Schrödinger cat states, squeezed coherent states, and lattice superpositions of coherent states. The latter superpositions can approximate several nonclassical states with high precision, hence their probability representation can describe various nonclassical states of the inverted oscillators. Explicit results are shown for the approximation of number states, photon number superpositions, and amplitude squeezed states by determining the parameters of the superposition appearing in the probability

In this letter, we propose a passively Q-switched all-fiber laser and demonstrate how to utilize a multimode double-clad Erbium–Ytterbium co-doped fiber as an active medium. The Q-switching is obtained based on the Kerr effect of multimode interference, which induced intensity modulation inside the linear cavity laser. Stable Q-switched pulses are obtained at 1552.3 nm with the repetition rate varying from 50.3 to 222.2 kHz, when the pump power is changed in the range from 1.00 to 3.09 W. We record the minimum pulse width and the maximum pulse energy at 2.1 μs and 2.7 μJ, respectively, at a pump power of 2.42 W. This proves a new modulation mechanism for obtaining high energy pulses based on all-fiber linear cavity.

We propose an efficient method for determining the position of the output plane of a phase object, which is registered by a lens system in the presence of a defocusing effect. The method involves the simultaneous employment of 2D diffraction maps of the diffracted wave constructed for its forward and inverse directions of propagation relative to the object output plane. We show that the resultant diffraction pattern obtained for both cases of the wave propagation appears as the two opposite directed diffraction cones with a special narrow zone between them. Within such a zone, there are particular regularities in the behavior of the intensity and phase shift of the wave. The knowledge of these regularities allows one to determine the position of the object output plane with micrometer accuracy, even when a single angle of laser probing is employed.

We fabricate a nanocomposite (NC) of polycarbonate (PC), Zinc sulfide (ZnS) and Nickel oxide (NiO) nanoparticle by the sol-gel and ex-situ casting processes. We trust that this study is novel in the area of the impact of laser on such NC. The Rietveld alteration of XRD records indicates that both the prepared ZnS and NiO have a nano-nature of an average particle size of 4 and 18 nm. Samples of the PC/ZnS-NiO NC films are exposed to numerous laser fluences (4 – 30 J/cm²). We investigate the resulting outcome of the laser exposure on the optical behavior of the NC films, using ultraviolet spectroscopy (UVs). Upon raising the fluence up to 30 J/cm², both the indirect and direct band gaps reduce. The Urbach energy exhibits a reverse trend. This can be attributable to the domination of chain crosslinks. Also, we detect the nature of microelectronic transitions, using the optical dielectric loss εʺ and find that the PC/ZnS-NiO NC films possess direct allowed transitions. Also, we study the laser induced modifications in the optical conductivity and dielectric parameters. Moreover, the optical coloration changes between the exposed samples and pristine are estimated. The pristine NC sample is uncolored. It shows significant color alterations upon the laser exposure. The induced improvements in the optical characters suggest that the laser is a convenient mean that permits the use of PC/ZnS-NiO NC in the optoelectronic devices.