Journal of Russian Laser Research最新文献

We describe the experimental implementation of high-resolution soft X-ray spectrographs, which are stigmatic throughout their operating range. The optical configuration comprises a grazing-incidence plane VLS grating and a broadband normal-incidence focusing mirror with an aperiodic multilayer coating structure. The operating range is defined by the aperiodic multilayer mirror in use (Mo/Si: 12.5 – 25 nm; Mo/Be: 11 – 14 nm). The spectral resolution is determined by CCD detector resolution and is numerically equal to the product of the plate scale and the double pixel size. Vertically spaceresolved laser-produced plasma spectra of multiply charged ions are presented. The spatial resolution is equal to about 26 μm, the double pixel size. We discuss the prospect of extending high-resolution stigmatic spectral imaging below 11 nm and outline the data of numerical calculations of broadband normal-incidence mirrors based on aperiodic Ru/Sr and La/B₄C multilayer structures.

We develop an all-optical two-state Pauli X logic gate, using two-dimensional nano-photonic crystals (PhCs) based on photonic-crystal semiconductor optical amplifier switches (pc-SOA). An all-optical two-state Pauli X logic gate device is implemented by exploiting the cross-gain modulation property of pc-SOA (XGM) and the frequency encoding technique, which is constructed using a nano-structured photonic-crystal-based waveguide formed by a 2D square lattice of GaAsInP rods in the air background. The Pauli X gate is constructed within a two-input–two-output channel system. We confirm the operation of an all-optical two-state Pauli X logic gate by two sets of simulation experiments. For the simulation process, we use the finite-difference-time-domain (FDTD) and plane wave expansion (PWE) techniques. The frequency range of the band gap structure is determined in the transverse electric (TE) mode. The pc-SOA is used here for its highly-packed design, less consuming power, very high power transmission, and very good execution of the logic system. The simulation result at the output channels is also checked with the help of the cross-gain modulation (XGM) process. A two-state all-optical Pauli X gate device has a very fast response time (~1 ps), allowing for very fast optical information processing, which is helpful in the field of quantum computation. The speed of operation is on the order of 1 THz. The confinement of light is controlled and dominated by the nano-photonic crystal-based device (PhCs), and the frequency encoding technique can be exploited to improve the performance of the logic system.

The energy distribution characteristics of fast axial flow CO₂ lasers demonstrate that they are often used for cutting and welding metal materials, and it is generally believed that they are not suitable for material heat treatment. In order to expand the application range of these lasers, we prepare graphene (Gr) reinforced high entropy alloy (HEA) coatings, employing this type of laser under loworder mode conditions by adjusting processing parameters and cladding powder composition through orthogonal experiments. Then we study the effect of laser processing parameters on Gr/Al_xCoCrNiTi composite coatings. The research results indicate that the optimum process parameters are as follows: the laser power P = 3200 W, the scanning speed V = 14 mm/s, the cladding powder thickness d = 1.2 mm, and the spot diameter D = 4.0 mm. We find that, under the optimum process parameters, the Gr/Al_xCoCrNiTi laser cladding coatings exhibit typical dendrites and equiaxed grains. The microstructure refines with increase in the Al content. The Gr/AlxCoCrNiTi laser cladding coating mainly consists of the face centered cubic (FCC), body centered cubic (BCC), and M₂₃C₆. Increase in the Al content promotes the formation of the BCC structure. The microhardness of Gr/Al_xCoCrNiTi composite coatings range from 550 to 725 HV. The hardness is related to the solid solution strengthening caused by Gr and Al. With increase in the Al content, the microhardness of the coating shows a trend to increase, the wear resistance first increases and then decreases. The wear resistance is related to the BCC content and cracks in the coating. Orthogonal experiments and coating performance indicate that, by adjusting laser processing parameters and alloy composition, it is possible for fast axial flow CO₂ lasers to prepare Gr/Al_xCoCrNiTi composite coatings under low-order mode conditions, which can expand the applicability of these lasers.

Using two definitions of the turbulent distance to characterize the laser beam propagation through atmospheric turbulence, we derive a general analytical expression for the beam spread η depending on the turbulence parameter T(α) with the generalized exponent α and on the initial second-order beam moments in the z = 0 plane. Larger values of η correspond to a larger influence of atmospheric turbulence on the laser beam. We subsequently apply the analytical expression of η to a partially coherent Hermite–Gaussian beam propagating through non-Kolmogorov turbulence and illustrate the properties of η by numerical examples. The results show that the η values first increase, reach their maximum for a generalized exponent α ≈ 3.11, and then decrease with increase in α. Also η decreases with increasing beam order and wavelength, as well as with increasing values of the generalized refractive-index structural turbulence parameter, beam waist width, and coherence parameter.

To overcome the low efficiency of traditional pyrotechnic solid-state laser energy conversion, we design a dust cloud pyrotechnic-pumped Nd :YAG laser based on the thermal radiation model and Lambert–Beer law, which effectively addresses the issue of self-absorption during the combustion of traditional pyrotechnic compositions. Therefore, the laser output energy increases significantly. A laser energy of 2.15 J with a pulse width of 50 ms is achieved using 150 mg KClO₄/Zr/Al in this work. The energy-to-mass ratio reaches 14.34 J/g. Compared with the traditional pyrotechnic solid-state laser, the Nd :YAG laser pumped by a dust cloud showed a lower light threshold, higher energy efficiency, higher saturation limit, and better safety. In this work, we presents a novel and feasible solution for the development of compact and safe high-energy lasers.

Short pulses are showing increasing importance in various industrial and scientific applications. Here, we exploit the saturable absorption of a ternary layered MAX-phase compound of Vanadium Aluminum carbide (V₄AlC₃) to produce mode-locked pulses in Erbium-doped fiber-laser (EDFL) cavity. The V₄AlC₃ composite thin film with a modulation depth of 24% is successfully obtained by embedding the commercial V₄AlC₃ powder into polyvinyl alcohol (PVA). It is integrated into an EDFL cavity, as a saturable absorber (SA), to generate a highly-stable mode-locked pulse, which operates at the 1559.8 nm wavelength. We successfully obtain the mode-locked pulse train with a fixed repetition rate of 1.8 MHz and a pulse width of 3.66 ps, as the pump power is set within a range from 73.1 to 108.1 mW. At the maximum pump power equal to 108.1 mW, the average output power, pulse energy, and peak power are 10.2 mW, 5.4 nJ, and 1.5 W, respectively. Overall, these results show the potential of V₄AlC₃ MAX-phase material to be used in ultrafast generation. The proposed approach is straightforward and can also be applied to operate in other wavelength regions.

In this paper, we propose a high-sensitivity two-core dual-polarization photonic-crystal-fiber surfaceplasmon-resonance (PCF-SPR) sensor based on Indium Tin oxide (ITO). ITO is a conductor material with adjustable photoelectric properties and low losses in the infrared range, and the two-core structure could better direct the incident light to the metal surface to enhance the coupling. According to numerical simulation results, the maximum wavelength sensitivities are 17,000 nm/RIU and 25,500 nm/RIU in the x-polarization mode and y-polarization mode. The maximum resolution of the x-polarization mode and y-polarization mode of the sensor can reach 5.88·10⁻⁶ RIU and 3.92·10⁻⁶ RIU, respectively, and the liquid refractive index detection range is 1.32 – 1.39. Taking into account the simple structure and excellent sensing performance, the sensor has wide application prospect and can accurately detect the refractive index of liquids, such as blood plasma, hemoglobin, etc.

Lasers with low-coherent radiation have attracted the attention since the first publications on this topic in the 1960s and up to the present time, thanks to their numerous applications. Compact lowcoherent lasers with a flow of the active medium through the pumped region can be done, using dense mixtures of solid particles and a liquid – slurry lasers. The preparation of slurry compositions based on particles like Nd :YVO₄ or Nd :YAG crystal granules meets certain difficulties associated with the use of liquids having high refractive indices, n ≈ 2. Here, we study the properties of a perspective Nd-doped slurry laser in model experiments, comparing parameters of Nd :YVO₄ and Nd :YAG slab lasers in compact plano-spherical resonators with and without a cuvette-diffuser on an immersion mixture of LiF crystal microparticles and isobutyl alcohol, n ≈ 1.39. At a laser diode pump power of 100 W, these lasers (without a cuvette) emit, in a quasicontinuous multimode regime, 1 ms pulses of low-coherent radiation (⋋ ≈ 1064 nm) with a divergence of 20 – 40 mrad and the 21 – 47 W power at the 10 Hz repetition rate. Under the same pumping conditions, we obtain a low-coherent radiation with the 1 – 6 W power and divergence up to 100 mrad in these lasers with a cuvette-diffuser. The spatial coherence of these lasers under changes in the pump current, pump spot sizes, and the state of immersion in the cuvette is estimated from the contrast C of the speckle patterns produced by the radiation. Also, we register C values in the region 0.02 − 0.04, comparable to the thermal sources contrast. The presented scheme demonstrates low-coherent Nd :YVO₄ and Nd :YAG lasers and show the feasibility of creating compact LD-pumped slurry lasers.

In this work, we investigate the performance of doped quaternary AlInGaN last quantum barrier (LQB) of deep-ultraviolet laser diodes (DUV LDs) without the electron blocking layer (EBL). The results indicate that the stimulated radiation recombination rate of the n–p-doped LQB structure increases. Compared with the undoped LQB structure, the threshold current of the n–p-doped structure of quaternary AlInGaN LQB for DUV LDs without EBL decreases from 43.79 to 36.59 mA, the slope efficiency increases from 1.20 to 1.28 W/A, and the threshold voltage increases from 4.62 to 4.63 V. These results demonstrate that the n–p-doped structure can significantly improve the performance of DUV LDs.

Based on the extended Huygens–Fresnel principle and the second-order moments of the Wigner distribution function (WDF), we derive the analytical formulas for the root-mean-square (rms) spatial width, rms angular width, and M²-factor of a partially coherent twisted elliptical vortex beam (PCTEVB) propagating through the inhomogeneous atmospheric turbulence. The spatial spreading, angular width, and M²-factor of a PCTEVB in turbulence are investigated numerically and comparatively. We find an interesting result that the relative rms angular width and M²-factor of PCTEVB with a small ellipticity propagating through turbulence decreases, meaning that the elliptical vortex beam is less affected by the inhomogeneous atmospheric turbulence in comparison with the traditional vortex beam. We also find that the relative M²-factor and the relative rms angular width of PCTEVB mainly depend on the topological charge, twist factor, initial coherent length, zenith angle, and propagation distance. In addition, the PCTEVB, with a small initial coherent length and ellipticity as well as a large twist factor, has a stronger anti-turbulence ability. Our outcomes may have future extensive possibilities in free-space optical communications.