It is natural for experimentalists to desire to fully explore the capabilities of their lasers, and to use them to their full potential in subsequent experiments. In the case of laser oscillators with resonators constructed with chirped mirrors [1] and/or completely sealed, these possibilities are quite limited. On the contrary, in classical femtosecond oscillators containing pair of prisms for intracavity dispersion control [2-4], this is possible and relatively simple. This is also the likely situation at the first stage of development of a home-built femtosecond oscillator. A prerequisite of course is, that the necessary diagnostic equipment is available. This paper is devoted to a detailed characterization of a Ti:sapphire Kerr-lens mode-locked femtosecond laser oscillator with an intracavity prism pair and an external sequence of chirped mirrors [5,6] to fully exploit the possibilities of tuning its output parameters.
Ultrashort laser pulses, characterized by pulse durations in the picosecond to femtosecond range, present significant potential for enabling ultra-high data rate transmission in optical communication systems. Understanding the propagation of these pulses in nonlinear media is critical due to the complex effects they encounter, including chromatic dispersion and various nonlinear phenomena. The propagation of ultrashort laser pulses in optical fibers is governed by the generalized nonlinear Schr & ouml;dinger equation (GNLSE), which incorporates effects such as self-phase modulation (SPM), cross-phase modulation (XPM), self-steepening (SS), and stimulated Raman scattering (SRS). This equation effectively models the interplay between dispersion and nonlinearity in various fiber structures, including silica fiber (SiO2), air-silica, photonic crystal fibers (PCFs), and Air-filled core. Analysis reveals that air-silica outperforms conventional fibers in terms of pulse compression and peak power handling. Our simulations reveal compelling pulse dynamics: an initial 8 ps pulse undergoes width compression to 4.04 ps, while its peak power intensifies from 1.23 kW to 69 kW upon propagation. Their reduced dispersion and nonlinear interactions make them optimal candidates for high-fidelity ultrashort pulse transmission.
A hybrid orthogonal frequency division multiplexing and optical code division multiple access techniques based bidirectional passive optical local area network (POLAN) system is designed and investigated for hospital applications. The results reveal reliable fiber, free-space and visible light communication range of 50km, 100m and 10-20m, respectively, at 10 & times;100Gbps data rate under clear air climate and weak turbulence scenarios. Also, the system offers maximum-8.5dBm received power, 1dB power penalty and it can serve upto 300 end nodes. Comparative literature reveals its design superiority over other existing designs in terms of design performance.
Femtosecond saturable and reverse saturable absorption in Hibiscus sabdariffa dye has been theoretically studied with 40 fs laser pulses at 515 nm and 1030 nm, respectively. Theoretical simulations agree well with reported experimental results. Ultrafast all-optical OR and AND logic gates at 515 nm, as well as NOT, universal NOR and NAND logic gates at 1030 nm have been designed based on optimization of nonlinear absorption to achieve enhanced contrast and low-power operation. An optical limiter and all-optical diode have also been designed demonstrating the material's ultrafast performance, tunability, stability, and versatility for practical applications.
In this work, DFT with plane-wave ultrasoft pseudopotential based on first-principles was used to investigate the Cs/Li-O co-adsorption on the GaAs(001)beta 2 (2 & times;4) reconstruction surface. Firstly, the structural distortion, stability, and ionicity were analyzed. Subsequently, the photoemission properties were investigated in detail from three perspectives: dipole moment, band structure, and optical properties. Results showed that during Cs only activation and Cs/O activation, the proper introduction of Li atoms could improve the photoemission, but it should be noted that the introduction of too much Li atoms would reduce of photoemission. The optimal ratio of Cs to Li is 4:2 and 5:1 during the Cs only activation and Cs/O activation respectively.
To address the demands for high-precision and wide-range pressure measurement, an all-fiber diaphragm-type Fabry-Perot pressure sensor was designed. Based on principles and simulation experiments, static pressure calibration and dynamic pressure measurement systems were set up to evaluate the sensing performance. Experimental results exhibit a wavelength sensitivity of 96.4 pm/MPa and a cavity length sensitivity of 5.14 nm/MPa in static pressure range of 0 similar to 60 MPa. In dynamic pressure measurements, shock wave signals were captured with a measured pressure peak of 4.02 MPa and a rise time of 114 ns. The sensor is suitable for high-temperature oil monitoring and others.
In the world of display technologies, lanthanide doped inorganic phosphors have become more popular in recent years. The suggested study uses a wet chemical approach to synthesize Tb3+, doped BaTiO3 phosphor. Phase Identification and vibrational features of proposed phosphor was confirmed using XRD and FTIR analysis. Under excitation at 351 nm, 368 nm, and 377 nm, the synthesized Tb3+ doped BaTiO3 phosphors showed blue and green emission peak at 452 and 545 nm photoluminescence spectra (PL). The potential application of the produced phosphor in WLEDs alongside additional display applications is supported by all of those results.
Zinc oxide thin films were deposited on thoroughly cleaned glass substrates using the spin coating technique and subsequently characterized by X-ray diffraction (XRD) and UV-Vis spectroscopy. The XRD patterns confirmed the formation of a hexagonal wurtzite crystal structure, with crystallite size found to increase progressively with annealing temperature, reflecting improved crystallinity. Structural parameters such as dislocation density and macrostrain were also evaluated and are reported in this study. UV-Vis spectroscopy studies reveal the film's optical parameters, which provided insights into transmittance, absorption coefficient, and extinction coefficient. The optical band gap was determined from the absorption spectra, with values ranging from 2.60 eV for the as-deposited film to 2.22 eV for the film annealed at 400 degrees C. The observed reduction in band gap with increasing annealing temperature is attributed to decreased defect density and enhanced crystallinity.
Free Space Optical (FSO) communication is a key technology for high-bandwidth, secure, and efficient wireless communication. This work investigates the performance of Hermite Gaussian (HG) laser modes in FSO systems undervarying atmospheric turbulence conditions. Using Mode Division Multiplexing (MDM), four HG modes (HG00, HG01, HG02, HG03) were transmitted over a single wavelength at a data rate of 1 Gbps. The system setup, modelled using Optisystem software, incorporated a Mach-Zehnder phase modulator (MZM) and spatial demultiplexer, operating at a wavelength of 1550 nm. Key Quality of Service (QoS) metrics, including Quality (Q) factor, Bit Error Rate (BER), and Signal-to-Noise Ratio (SNR), were evaluated to assess the impact of turbulence, attenuation, and geometrical losses. The findings indicate that the fundamental mode HG00 consistently outperformed higher-order modes due to its simpler intensity distribution. The four HG modes under consideration shows significant Q factor and BER up to 900 meters under low turbulence conditions. Although under strong turbulence regime HG00 shows Q factor of approximate to 12 for 600 m link range whereas the Q-factor for higher-order HG modes degrades significantly to around 6. The results underscore the need for advanced modulation techniques and adaptive methods to enhance FSO system reliability in challenging atmospheric conditions.
Using the Heyd-Scuseria-Ernzerhof screened hybrid functional, we systematically investigate the electronic structure and optical properties of cubic Ce0.5La0.5AlO3 under varying pressure. The lattice constant decreases significantly as pressure increases. For electronic properties, the band gap exhibits a steady reduction with rising pressure. Meanwhile, the bandwidths of two higher valence bands and conduction band increase, though the lowest valence band remains unaffected. Optically, pressure enhances the strongest peak of the imaginary part of the dielectric constant, induces a slow increase in the static dielectric constant, and causes distinct blue-shift in the prominent peaks of the absorption coefficient, reflectivity, and energy-loss function.
This paper investigates the effect of the placement of a thin-film absorber layer on the absorption coefficient of microbolometers. The absorption variation is analyzed by changing the absorber layer position through simulations using the cascaded transmission line model. Relocating the absorber layer increases the absorption coefficient from 69% in the classical design to 85%, which corresponds to a 23% relative increase in detector performance. The novelty of this study lies in the investigation of absorber layer placement, which has not been addressed in previous works. This improvement, achieved by a simple rearrangement of the layer sequence, offers a cost-effective method to enhance microbolometer performance.
The paper presents the first investigation of the clouds' dynamics over the 2024-2025 winter season in Magurele, Romania. The vertical wind speed provided by a Doppler wind lidar (DWL) and two Doppler cloud radars (DCR) is analysed. Four case studies are shown which refer to two low-to mid-altitude clouds (both ice and mixed phase cloud), a high-altitude cloud (mostly ice cloud) and one extended towering cloud (mostly ice cloud). While the same analysis was performed on all cases, only the 11 December 2024 example is detailed in the main text whereas the remaining cases are provided in annexes. In the selected case studied, the vertical speed determined from DWL is slightly higher than the speed determined from the two DCR, especially in the mixed phase region (upper part of the cloud) which shows the DWL capability to better sense this type of cloud. The correlation coefficient between the wind speed determined by DWL and a DCR is 0.78 (RPG) and 0.75 (MIRA) for the low-to mid-altitude cloud on 11 December 2024. For the high-altitude cloud, the correlation between DWL speed and DCR speed is 0.54 (both radars) could be due to the fact that DWL is not capable of sensing the entire cloud. DWL can provide valuable information of finer structures in a mixed phase region of a low to mid-altitude cloud, the final vertical speed profile should be considered based on information received from both the DWL and a DCR. This study highlights the value of combining Doppler wind lidar and Doppler cloud radar measurements to improve the characterization of vertical cloud dynamics across various types of clouds and altitude ranges during winter conditions.
A more efficient utilization of carrier frequencies to transmit data has recently emerged in the wireless bearer domain. The current research focuses on wireless communication with substantial data speeds and enhanced security. This article concentrates on designing a triangular lattice Photonic crystal (PhC) antenna structure and conducting subsequent research on its performance. The article offered a unique patch integrated with a diamond air holes PhC structure using the CST tool. The investigation of the proposed antenna is carried out using distinct sizes of diamond air holes and lattice constants of triangular PhC structure. In scenario 1, the diamond air hole in the triangular lattice PhC antenna design is varied between 2 and 6 & micro;m in size to determine the optimal PhC antenna. Whereas, in scenario 2, the lattice value is varied from 13 to 23 & micro;m. Based on the simulated results of two cases, the optimal PhC antenna produces the extreme results of -70.69 dB return loss (RL), 1.0058 voltage standing wave ratio (VSWR), and 8.74 dBi gain at 2.1 THz frequency. The proposed antenna frequency 2.1 THz is highly appropriate for future beyond 6G communication with enhanced data rate from giga to tera bits. The frequency band between 1-3 THz is optimal for various sensing and imaging applications. Especially 2.1 THz is great choice of non-destructive testing, hidden object detection since THz waves does not harm to humans.
Based on an analysis of the absorption and emission cross-section spectra of the 1%Er3+: LiNbO3 crystal in the spectral range 1450-1650 nm at room temperature the parameters of radiation-balanced generation were calculated. The optimal pump wavelength (1545 nm) and the RB generation wavelength (1610.8 nm) were determined. The corresponding efficiency and gain coefficients were calculated as F-eff = 2.40 & times; 10(-22 )cm(2) and F-gain = 4.62 & times; 10(-22)cm(2), respectively.
This study comprehensively explored the various characteristics of SrSnO3 when subjected to a mechanical load with the help of an ultrasoft pseudopotential (USP) and the generalized gradient approximation (GGA). The crystal lattice remains cubic, but a significant decrease of 11% in the lattice parameters and a 29% decrease in the lattice volume are observed. Moreover, no phase transformation is observed. The mechanical load not only affects the electronic structure but also impacts the way the material responds to optical load, including properties such as reflectivity, refractive index, absorption, energy loss function, and complex dielectric function. The increase in the absorption peak and the shift of these peaks to higher energies confirm the occurrence of a blue shift, which renders this material an attractive aspirant for optoelectronic applications. Furthermore, the material is inflexible, rigid, and mechanically stable and shows high resistance to shear deformation, which is confirmed by computing various mechanical parameters, including the Young, shear, and bulk moduli. Moreover, the Cauchy pressure, Pugh/Frantsevich ratio, and Poisson's ratio revealed the metallic bond structure, ductile behavior, and high-pressure strength of the material. The electronic band structure (BS) of SrSnO3 changes from a narrow band (0.135 eV) to a wide band (4.682 eV). The total, partial, and elemental partial density of states (TDOS/PDOS) were recorded for the analysis of the electronic band structure. It is the best material to be utilized as an ultraviolet filter since its absorption spectra are present in the UV range. Moreover, its absorption, high conductivity, refractive index, and reflectivity make it an exceptional component in optoelectronic devices.
Lithium-ion batteries have been widely researched for academic and industrial applications owing to their high energy density, safety, versatility, and long life in recent years. The cathode material plays a crucial role in determining the energy density, voltage, and overall battery performance. Among cathode materials, o-LiMnO2 has a higher energy density and operating voltage than its counterparts in other phases and structures. Herein, we successfully synthesized o-LiMnO2 without impurities or secondary phase formation by controlling the temperature of hydrothermal synthesis. We have investigated the surface morphology of the synthesized LiMnO2 nanoparticles using SEM method. The structural properties obtained using XRD and XPS. These results demonstrate that temperature plays a critical role in determining the phase purity and crystallinity of the sample. The purest orthorhombic structure of the LiMnO2 nanoparticles was observed for the sample synthesized at 200 degrees C for 14 h. LiMnO2 based electrode (LiMnO2 :CB:PVA (80:11:9)) were coated onto an ITO/glass substrate using the Dr. Blade method. Then, the electrochemical properties of electrode were investigated using the threeelectrode method. The highest amounts of intercalated and deintercalated charge densities were obtained for the purest orthorhombic LiMnO2 phase. This simple and efficient synthesis method are a promising approach for future studies of o-LiMnO2, as it has improved structural stability and electrochemical properties compared to other LiMnO2 polymorphs, making it a potential candidate for use in high-performance lithium-ion batteries.
In this paper, we present an improved mobility model for charge transport in organic semiconductors by inserting the field dependent effective temperature instead of the real temperature into the temperature dependence of the mobility. The consistent descriptions with equal quality for the temperature and composition dependent current density-voltage characteristics of the hole-only devices based on TQ1:PC71BM:IC60BA ternary blends can be obtained by using the extended Gaussian disorder model (EGDM) and our improved model, respectively. However, the extracted values of average intersite distance a from the two models are quite different. The values of a from our improved model are very close to the typical value of organic semiconductors, and are obviously smaller than that from the EGDM, indicating that our improved model can provide a more appropriate description of the electric field and temperature dependence of the mobility than the EGDM.
Spinel ferrite system with chemical formula MgXMn1-XFe2O4 (x = 0.0-0.5) having nanoparticle size (25-40 nm) were prepared by coprecipitation technique. X-ray diffraction patterns show single phase of the material, EDAX study shows stoichiometry of the samples, whereas particle morphology was studied by means of Transmission electron microscopic analysis (TEM), particles are found to have spherical in nature. In our previous communications we have reported the effect of Mg2+ substitution in change of particle shape from spherical to needle shape and on the magnetic properties. In the present work we have studied influence of Mg2+ substitution on particle size distribution with the help of differential size distribution (DSD) and Cumulative undersize distribution (CUSD) curves for two representatives amples x = 0.2 and 0.4 for the system MgXMn1-XFe2O4.
This study investigates the design and performance of a compact fan-shaped antenna optimized for radar and satellite communication applications. The proposed antenna, measuring 40 & times; 50 & times; 0.8 mm(3), is fabricated on an FR4 substrate and fed using a 50 Omega microstrip line. Its performance was evaluated through full-wave simulations and validated experimentally using a Vector Network Analyzer. The antenna operates effectively at multiple resonant frequencies 2.05, 3.39, 5.34, 6.37, 7.38, 8.54, and 9.85 GHz achieving return loss values between -12.91 and -24.07 dB, with corresponding VSWR values from 1.13 to 1.58. A maximum gain of 9.11 dBi and bandwidths of up to 300 MHz were observed, with close agreement between simulated and measured results.
The photoinduced anisotropy's dynamics of PMMA/Disperse Red 13 (PMMA/DSR13) thin films were investigated by the pump-probe method. The anisotropy increased exponentially at the start of pumping, and reached a photostationary state due to the photoisomerization process. However, anisotropy decreased exponentially as soon as the irradiation was switched off. It was concluded that the Angular Hole Burning (AHB) and the Angular Redistribution (AR) effects are responsible for the observed dynamic photoinduced anisotropy (POA). Moreover, the relative POA revealed that the photoisomer's thermal isotropic relaxation was insignificant, in comparison with the anisotropic reversible photoisomerization that occurred at cutting-off the pump.
