Journal of Russian Laser Research最新文献

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.

We construct and characterize a small-size fast-axial-flow RF-excited CO₂ laser. The laser, including a pair of 10 cm long electrodes symmetrically positioned around a quartz tube, is driven by an RF generator with the 1 kW maximum power at a frequency of 13.56 MHz. The output power and efficiency of the laser are experimentally measured under different structural and operational conditions, such as the discharge tube diameter, width and length of electrodes, as well as the input RF power. The width of the electrodes is changed in such a way that the ratio of the total width of electrodes to the perimeter of the discharge tube (the so-called geometric ratio) varies in the 0.3 – 0.6 range. The diameter of the discharge tube is also changed in the 20 – 30 mm range. The results show that, for every given discharge tube diameter, optimum performance of the laser is obtained for 0.4 and 0.5 values of the geometric ratio. Although, a maximum output power of 63.5 W can be obtain applying the 1 kW input power, using the 2.6 cm discharge tube diameter, 0.6 geometric ratio, and CO₂ :N₂ :He=1 : 3 : 5 gas mixture at the 90 mbar total pressure. However, an optimum laser efficiency of 7.2% is reached under this condition for the 57.5 W output power. Further, the highest total output power and output power per unit length of the electrodes are obtained for the 20 and 10 cm electrode lengths, respectively.

This paper was stimulated by the experimental studies of solid-state lasers initiated by N. G. Basov and carried out at the Laboratory of Luminescence of the P. N. Lebedev Physical Institute under the direction of M. D. Galanin and A. M. Leontovich in the 1960-ies. Here, the classical parabolic equation method is extended in order to calculate complex eigenfrequencies of optical oscillations in a dielectric-filled open resonator. Accurate estimates confirm a high quality factor of ruby lasers. The developed approach can be used to find complex eigenfrequencies of other dielectric optical objects in laser systems of current interest.

Based on the extended Huygens–Fresnel principle, we derive the analytical expression of the crossspectral density matrix of a partially coherent Laguerre pulsed vector vortex beam (PCLPVVB) propagating through isotropic and anisotropic atmospheric turbulence. Our outcomes reveal that the atmospheric turbulence affects the evolution of spectral intensity distribution of PCLPVVB, and the beam quickly degenerates on propagation in the strong turbulence. We also can find that PCLPVVB with a larger topological charge has a stronger ability to resist the degeneration caused by atmospheric turbulence in comparison with the non-vortex beam. In addition, increasing the initial coherence length and mode order can increase the anti-turbulence ability of PCLPVVB, and the pulse duration significantly affects the spectral intensity of PCLPVVB in turbulence. Our research results are important for some applications in laser radar detection, remote sensing, and free-space optical communication.