Journal of Russian Laser Research最新文献

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.

The graphene (Gr) reinforced CoCrFeNiTi high-entropy alloys (HEAs) were prepared, using laser cladding technology based on CO₂ gas laser. The effect of Gr on microstructure, mechanical properties, and corrosion resistance of the HEAs is studied. The experimental results indicate that the main microstructure of Gr/CoCrFeNiTi HEAs is equiaxed grains, with precipitated phases filled between the grains. Graphene plays a role in refining grains. The Gr/CoCrFeNiTi HEAs composite coating consists of the face centered cubic (FCC), body centered cubic (BCC), and M₂₃C₆ in-situ formed carbides. Graphene ptroduces the effect of promoting the formation of BCC and M₂₃C₆ carbides. The coatings hardness tends to increase with the increase of Gr addition, and the hardness is closely related to solid solution strengthening, fine grain strengthening, and dispersion strengthening. As Gr increases, the both wear resistance and corrosion resistance increase first and then decrease. The hardness, Gr, and the content of hard and brittle carbides in the coating have impact on the wear resistance.

Space division multiplexing (SDM) Erbium/Ytterbium (Er³⁺/Yb³⁺) co-doped seven-core fiber amplifier is one of the potential configurations used to accommodate the rapid development of the capacity of optical fiber transmission systems. To increase the demand transmission capacity and enhance the gain characteristics limited by only Erbium-doped multicore fiber amplifier for SDM-WDM system, we propose and simulate an enhanced architecture technology based on combining SDM and wavelength division multiplexing (WDM) Erbium/Ytterbium (Er³⁺/Yb³⁺) co-doped seven-core fiber amplifier. The architecture proposed allows us to obtain a peak gain over 49 dB and a gain greater than 20 dB in a large band with a minimum noise, which is lower than 6 dB in this amplified bandwidth.

In this work, we investigate the optical frequency transmission with a magnitude of 100 mW through a 20 m polarization-maintaining fiber, using the phase noise compensation method. In order to minimize potential noise caused by stray light reflections in the fiber, we incorporate two acoustic-optic modulators to spectrally separate the heterodyne signal, effectively suppressing these sources of noise. Our experimental results demonstrate that the modified Allan deviations of fractional frequency stability for 1 s and 10,000 s are approximately 2.5 · 10⁻¹⁷ and 1 · 10⁻²⁰, respectively. This research contributes to the advancement of high-power optical frequency transmission via optical fiber.

In the natural light imaging scene, it is often illuminated by a variety of wavelength light sources. To obtain images with better robustness and richer information, in this paper, we propose a method of visible and infrared image fusion based on ghost imaging, which fully combines the advantages of visible and infrared imaging. In fact, two single wavelength illumination information and detection values are used for correlation reconstruction, and then the target information is obtained, using the New Sum of Modified Laplacian. Due to the combination of the advantages of dual-wavelength imaging, as a result, complementary information on the same object can be collected to comprehensively reconstruct the information on the object and reproduce the complete detailed information, thus promoting the development of multi-wavelength fusion technology in the field of imaging.

We present an efficient continuous-wave deep-red Pr :YLF laser with a double-pass-pumping architecture. The fiber-coupled blue laser diode is used as the pump source. With an incident pump power of 15.3 W, the deep-red Pr :YLF laser reaches the 5.02 W output power at 720.8 nm, corresponding to a slope efficiency of 40.2%. In addition, we estimate the beam quality factor to be about 2.0.

In this paper, we focus on the performance optimization of Holmium-doped fiber amplifier (HDFA) for wavelength-division-multiplexed (WDM) optical communication system in the 1990 – 2100 nm wavelength range at higher bit rates. We investigate the proposed amplifier for 12×100 Gb/s WDM system at channel spacing of 10 nm. An average gain and noise figure of 32.17 and 8.2 dB, respectively, are obtained over the selected wavelength range at −25 dBm optimum input power per channel. An optimized Holmium-doped fiber (HDF) length of 9 m and HDFA-pump wavelength of 1950 nm are used. The operation and resulting gains of HDFA are also compared when pumped at different pumping wavelengths of 1890, 1950, and 2010 nm (fiber-laser-pumped HDFA) and 1150 nm (diode-pumped HDFA). Furthermore, the impacts of varying such parameters as the input signal power, HDF length, Ho³⁺ concentration, and HDFA pump power on gain are also investigated.

We propose and demonstrate a passively mode-locked all-fiber laser utilizing a multimode interference effect in graded-index multimode fiber (GIMF). The mode-locking is obtained due to the Kerr effect in GIMF, which induces the intensity modulation inside the ring cavity laser. We obtain stable soliton mode-locked pulses at a center wavelength of 1574.1 nm, with a fixed repetition rate of 22 MHz and a pulse duration of 650 fs, when the pump power is changed in the range from 66.2 to 140.0 mW. The maximum average output power and pulse energy are recorded at 9.82 mW and 448 pJ, respectively, at a pump power of 140 mW. This proves that a nonlinear optical response in GIMF can be used as a new modulation mechanism for obtaining ultra-short pulses based on all-fiber ring cavity.

We theoretically study resonant hyper-Raman scattering of light by 2 LO phonons in a CdS crystal with the wurtzite structure. The scattering process involving the two-photon dipole transitions to B and C excitons of the s-type is considered. The different sequences of intermediate states are taken into account. It is shown that the inclusion of the possible dipole transitions to the deeper valence band, at certain conditions, can have a noticeable effect on the frequency dependence of the scattering cross section.