Journal of Russian Laser Research最新文献

This study reports a passively Q‑switched 2 μm Tm:YAP solid-state laser employing an NbSe₂/MoS₂ heterojunction as the saturable absorber. At an absorbed pump power of 10.7 W, a maximum pulse repetition rate of 126.49 kHz was achieved, together with a minimum pulse width of 630.6 ns, a maximum single-pulse energy of 12.97 μJ, and a highest peak power of 20.6 W. These results demonstrate that the NbSe₂/MoS₂ heterojunction enables stable high-repetition-rate pulsed operation and is an effective saturable absorber for passively Q‑switched 2 μm solid-state lasers. The achieved high repetition rate makes the laser attractive for applications in high-speed precision micromachining and LiDAR.

The increasing demand for high-performance computing is driving innovation in traditional electronic hardware. Integrated photonics has emerged as a promising solution due to its advantages in terms of parallelism, bandwidth, and low power consumption. The present study introduces a compact photonic computing chip built on micro-ring resonators. The experimental outcomes demonstrate accuracy rates of 97.09% and 97.23% on the IRIS and MNIST datasets, respectively, highlighting its potential for scalable and efficient photonic computing systems.

This work presents the design and numerical analysis of a two-dimensional photonic crystal (2D-PhC) biosensor platform for refractive-index sensing of biological fluids such as urine and blood. The proposed platform integrates three vertically aligned ring-shaped microcavities within a silicon photonic crystal structure optimized to operate near the 1550 nm resonance. The device was evaluated using refractive-index values for biological samples associated with glucose concentration, high-density lipoprotein (HDL) cholesterol, sickle cell anemia, and HIV infection. The sensing mechanism is based on monitoring shifts in the resonant wavelength caused by variations in the refractive index when biological analytes infiltrate the microcavities. The structure is modeled and simulated using RSoft Photonic Suite CAD environment.

Simulation results demonstrated that the proposed biosensor achieves a sensitivity exceeding 1100 nm/RIU. With a Q-factor on the order of 10⁶, a figure of merit (FoM) of approximately 10⁶ RIU⁻¹, and a limit of detection close to 10⁻⁷ RIU. These results indicate that the proposed photonic crystal platform can serve as a compact, label-free, and non-invasive sensor for high-sensitivity refractive index sensing in biological fluids.

Background: Diabetes often slows wound healing and can cause chronic ulcers. This study examined how Platelet-Rich Plasma (PRP), Low-Level Laser Therapy (LLLT), and their combination affect healing in diabetic rabbit wounds.

Methods: Fourteen days after diabetes was induced, researchers created standardized wounds on the backs of 44 diabetic rabbits. The rabbits were randomly assigned to four groups: control (saline), PRP, LLLT, and PRP + LLLT, with 11 rabbits per group and two wounds per rabbit. PRP was prepared just before use. LLLT was applied once daily for 14 days using a non-contact method. Wound closure was assessed with digital photos on days 7, 14, and 28, and the percentage of fully closed wounds was recorded. Biomechanical tests were performed on days 14 and 28. Statistical analysis accounted for the two wounds per rabbit using Generalized Estimating Equations and Linear Mixed Models (LMM) with Tukey adjustment.

Results: The proportion of closed wounds differed significantly among groups at day 7 (p = 0.013), day 14 (p = 0.001), and day 28 (p = 0.001). At day 28, the highest closure rate was observed in the PRP + LLLT group (86.3%), followed by LLLT (68.2%), PRP (54.5%), and control (22.7%). After adjustment for within-animal correlation, all interventions significantly improved wound closure compared to control; however, differences between LLLT and PRP alone were not statistically significant. Combination therapy demonstrated greater biomechanical strength than PRP alone, but its superiority over LLLT alone was not statistically significant for most outcomes.

Conclusion: Both PRP and LLLT improved diabetic wound healing in this rabbit model. The combination of PRP + LLLT yielded the most favorable late-stage outcomes, especially compared to PRP alone, but its superiority over LLLT alone remains inconclusive. Proper statistical correction for clustering is essential in wound-healing studies involving multiple wounds per animal.

Using time-dependent density functional theory coupled nonadiabatically with molecular dynamics (TDDFT-MD), we systematically investigate the real-time nonadiabatic electron-nuclear dynamics of cytosine irradiated by 800 nm (1.55 eV) laser pulses. The laser intensity ranges from 1(times10^{13}~text{W/cm}^2) to 8(times10^{15}~text{W/cm}^2). The calculated ground-state electronic structure, highest occupied molecular orbital (HOMO) distribution, and optical absorption spectrum are in excellent agreement with experimental data, validating the theoretical model. Two distinct ionization regimes (multiphoton, (gamma > 1); tunneling, (gamma < 1)) are identified, with distinct orbital contribution mechanisms and structural responses. In the multiphoton regime, ionization exhibits a near-resonance energy alignment tendency. HOMO‑3 contributes the most (20.8%) owing to its favorable (sigma)-type spatial symmetry without nodal planes perpendicular to the laser polarization, together with near-resonant energy matching with six-photon energy. In the tunneling regime, the intense laser field depresses the Coulomb barrier, activating deep orbitals and reducing the total contribution of the four outermost orbitals to 22.5%. Laser intensity modulates structural stability: low intensities induce small-amplitude vibrations without dissociation, while high intensities trigger NH/CH bond cleavage via intramolecular Coulomb repulsion, with the pyrimidine ring remaining intact. The ionization yield follows a power-law relationship with laser intensity in both regimes, with logarithmic slopes of 3 (multiphoton) and 0.8 (tunneling), reflecting intrinsic differences in ionization mechanisms. This work provides atomic-level insights into cytosine’s strong-field dynamics, laying a foundation for understanding laser-DNA interactions.

High efficiency, single-band light absorption at the nanoscale plays a vital role in advanced applications such as photothermal conversion, optical sensing, and biomedicine. Here, we propose a vertically stacked hybrid structure composed of aluminum arsenide (AlAs), indium tin oxide (ITO), and gallium arsenide (GaAs). We systematically investigate its absorption characteristics at a wavelength of 1240 nm. When light is incident from the GaAs side, a pronounced localized field enhancement occurs within the structure, leading to a peak absorption efficiency of 92%. Furthermore, the structure exhibits a temperature modulation efficiency of 60.8%, indicating its potential for broadband thermal tuning of absorption. Additionally, the AlAs/ITO/GaAs sandwich configuration demonstrates distinct nonreciprocal optical behavior, meaning the absorption response differs significantly depending on the illumination direction. These results provide a new strategy for designing multifunctional optoelectronic devices that integrate high absorption, thermal tunability, and directional optical response.

To achieve uniform side-pumping of solar multi-disk laser and improve the output power, a solar concentrator system based on a parabolic mirror (f = 850 mm, sunlight-recieving area of 8 m²) and a circular compound parabolic concentrator (CPC) is proposed. Based on the compensation method, the uniform side-pumping of three Nd:YAG disks (Φ17 mm×2 mm) can be achieved. Ray tracing demonstrates that the absorbed pump power of the disk array is 1100 W, and the uniformity of the radial pump light distribution of each disk exceeds 92%. The laser output power and the collection efficiency reach 381 W and 47.6 W/m² in theory. It can provide a new idea for high power solar-pumped solar multi-disk lasers.

The surface modification of molybdenum under picosecond laser irradiation was systematically investigated, with particular emphasis on establishing a quantitative link between plasma parameters and ablation crater morphology. A picosecond Nd:YAG laser operating at a wavelength of 1064 nm with a pulse duration of 28 ps was used to irradiate molybdenum samples at laser fluences of 34.06, 36.59, and 38.02 J/cm². Ablation efficiency was evaluated by measuring crater diameters via surface profilometry, and the resulting surface morphology was examined by scanning electron microscopy (SEM). Laser-induced breakdown spectroscopy (LIBS) was employed to determine the fundamental plasma parameters. The electron temperature was found to vary within the range of 12,263–12,781 K, whereas the electron density decreased from (0.55 times 10^{18}) cm⁻³ to (0.40 times 10^{18}) cm⁻³ with increasing laser fluence. A strong negative correlation ((r approx -0.99)) between electron density and ablation crater diameter was identified, indicating that plasma shielding is the dominant factor limiting material removal at higher fluences. The key novelty of this work lies in the experimental demonstration of a self-regulating plasma regime during picosecond laser ablation of molybdenum, in which inverse bremsstrahlung absorption and plasma expansion provide a feedback mechanism that stabilizes both plasma parameters and crater dimensions. This quantitative correlation among electron density, plasma absorption, and crater formation has not been reported previously for molybdenum under picosecond irradiation. The results obtained advance fundamental understanding of laser-plasma-matter interactions and provide practical guidelines for high-precision laser micromachining of refractory, high-melting-point metals.

In this study, we propose and experimentally demonstrate a new mode-locked fiber laser configuration in which a large-core erbium-doped fiber (EDF) simultaneously functions as the gain medium and an artificial saturable absorber (SA). A 70 cm-long, highly doped large-core EDF was incorporated into a simple all-fiber ring resonator, eliminating the need for any additional conventional SA device. Stable soliton mode-locking was achieved through nonlinear multimode interference occurring within the large-core EDF. The excitation and interaction of multiple transverse modes under high optical intensity produced intensity-dependent transmission, effectively enabling self-starting pulse formation. The laser generated stable soliton pulses centered at 1564.1 nm with a pulse duration of 330 fs. Mode-locking was maintained over a pump power range from 291.6 to 319.2 mW, demonstrating good operational stability. Owing to the short cavity length—since the same EDF segment serves dual roles as both gain medium and artificial SA—the laser achieved a relatively high fundamental repetition rate of 24.1 MHz. The maximum pulse energy reached 143.5 pJ. This compact and simplified architecture highlights the potential of large-core EDF as a multifunctional nonlinear element for efficient ultrafast pulse generation without relying on discrete SA components.