Abdullah, MundzirAziz, M. S.Krishnan, GanesanAhmad, Fauzan...
8页
查看更多>>摘要：The third-order nonlinear optical response of Clitoria ternatea (CT) petal's dye in various solvents were characterized via Z-scan technique with a diode pumped solid state (DPSS) laser at 532 nm. The observations from the closed aperture z-scan showed the dye possess a self-defocusing effect with a negative nonlinear refractive index, n(2) with a moderate magnitude of real part of the third order nonlinear optical susceptibilities, Re chi((3)) of the order of 10(-10) esu. Open z-scan results showed that the CT dyes samples demonstrate a reverse saturable absorption (RSA) with strong two-photon absorption (TPA) coefficients, beta similar to 10(-3) cm/W, corresponds to large imaginary parts, Im chi((3)) in the order of 10(-5) esu. The highest values of n(2) and beta was observed in CT dye in ethanol and dimethyl sulphoxide, respectively. Not only the linear absorption spectra depends on the type of solvent used, but also the nonlinear characteristics are drastically influenced by it. On the whole, large chi((3)) of the dye samples were found to be in order of 10(-5) esu. Based on the measured value of nonlinear susceptibility, chi((3)), the natural dye derived from CT petals can be a candidate for applications such as optical limiting and switching.
查看更多>>摘要：This work reported the optical and radiation shielding features of fluorotellurite glasses with varying contents of TeO2, ZnF2, and BaF2 (coded as TeZnBa glasses). The refractive index of the glasses was found to be in the range of 2.27-2.31, while the dielectric constant is the range of 5.15-5.32, and the optical dielectric constant between 4.15 and 4.31. It was found that the reflection loss varies from 0.1561 to 0.1511 with BaF2 content increasing from 10 to 30 mol% while it varies from 0.1554 to 0.1507 at constant BaF2 content (10 mol%) and varying ZnF2 content (20-30 mol%). On the other hand, we explored the application of this glass system for radiation shielding by comparing its competency with other similar glass materials. We used the mass attenuation coefficient (MAC) and the effective atomic number (Z(eff)) as two essential radiation shielding parameters. We compared the mass attenuation coefficient (MAC) for the TeZnBa glasses with TeO2-Li2O-ZnO glass system at 0.662 MeV. We found that the TeZnBa1 has close MAC with 80TeO(2)-15Li(2)O-5ZnO glass, whereas TeZnBa4 has close MAC with 65TeO(2)-15Li(2)O-20ZnO glass. Also, we compared the MAC for the TeZnBa glasses with ZnO-MoO3-TeO2 glass system. The comparison demonstrated that TeZnBa1 has very close MAC with 20ZnO-20MoO(3)-60TeO(2) sample, while TeZnBa2 and TeZnBa3 have better attenuation ability than all the ZnO-MoO3-TeO2 glass system. We also compared the MAC for the selected glasses with other glasses contain heavy metal oxides such as BaO-Li2O-B2O3 and Bi2O3-SiO2-Al2O3 glass systems.
查看更多>>摘要：In this work an 8-channel DWDM demultiplexer is proposed with multiple designs and numerical analysis. Photonic crystal ring resonators of airholes on a 220 nm thick silicon slab are used as wavelength selective elements. Demultiplexers of three different designs are considered and their characteristics are analyzed. For all the three designs, the resolved wavelengths are in the range of 1530-1540 nm, where Erbium Doped Fiber Amplifiers are applicable. For the optimized device, the average coupling efficiency, cross talk are found to be 70.4% and -16.76 dB, respectively. Maximum and minimum coupling efficiencies of 79% and 56% are achieved. Photonic bandgap computation is performed by using plane wave expansion method and spectral characteristics are obtained by applying 3D finite difference time domain method.
查看更多>>摘要：A highly stable extended-cavity diode laser (ECDL) plays a crucial role in precision measure-ments. In this study, we propose a method based on the sound-solid coupling principle to measure the natural frequency of an extended-cavity diode laser. A frequency range of 0-2 kHz was employed to drive the ECDL, and the intrinsic frequency was obtained intuitively through the detuned saturation absorption spectrum. We compared the simulation and experimental results to validate the feasibility of the proposed method. Moreover, the structure of the laser was improved, and a new mechanical laser structure was designed and manufactured to suppress low-frequency resonance. The proposed method can help optimize the laser structure and improve the overall stability of the atom gyroscope.
Asadiyan, Mohammad HosseinParhoodeh, SaeedNazem, Saeed
11页
查看更多>>摘要：In this study, a butane (C4H10) gas sensor was simulated and fabricated using the surface plasmons resonance phenomenon. In this research, a thin layer of silver covered by a thin layer of magnesium fluoride (MgF2) was used to create surface plasmons. The most suitable thickness of silver and magnesium fluoride thin films for fabrication of butane gas sensor was determined by using computer simulations as well as laboratory experiments of 56 nm and 13 nm, respectively. With the aid of a BK7 prism and the Kretschmann configuration, surface plasmons were generated in the silver layer. Nitrogen gas was used to dilution of butane gas concentration. The fabricated sensor was tested and evaluated at different concentrations of butane gas. The sensor test results showed that this sensor is very sensitive to the concentration of butane gas, and changes in the concentration of this gas cause significant displacement at the peak location of the creation of surface plasmons.
查看更多>>摘要：The fast, simple, sensitive, and selective detection of sulfamethoxazole would be essential for water quality monitoring. Herein, we report a novel development of an optical sensor based on an organic/inorganic hybrid molecule (2-HAMP)(2)[CoBr4]. The physico-chemical properties were characterized using Fourier-transform infrared (FTIR), and Raman spectroscopies. The complex formation ability of (2-HAMP)(2)[CoBr4] toward sulfamethoxazole was investigated by UV-vis absorption. The complex stoichiometry was shown as 1:1. A glass plate was modified with a (2HAMP)(2)[CoBr4] hybrid compound and was characterized by scanning electron microscopy (SEM). The proposed optical sensor exhibits a linear response to sulfamethoxazole ranging from 10(-8) M to 10(-5) M, with a detection limit of about 8.6 10(-9) M and a response time of 130 s. In addition, the optode film shows good selectivity toward sulfamethoxazole with an RSD of 4.6%. Therefore, the as-proposed optode film shows excellent reproducibility, stability, sensitivity, selectivity, and a low time of response and limit of detection, which bodes well for its application in the process of water safety control.
查看更多>>摘要：This work presents a machine-learning based method for temperature error compensation of fiber optic gyroscope (FOG). Alternative to existing methods for constructing samples by single data point, a novel method of constructing samples by sequence is proposed, which fully considers the hysteresis and delay of temperature error. Moreover, temperature experiments with three distinct temperature trends, i.e., heating, holding and cooling, are conducted. Following the construction of training and test sets, the relevant training and test processes are completed using SVR algorithm. According to the degree of approximation in predicted value relative to the real value and the degree of improvement in gyro stability, the effects of various sample construction methods on the corresponding error compensation are analyzed. Considering the root mean square error (RMSE), mean absolute value error (MAE) and improvement-factor of FOG zero-bias stability as measurement indicators, this work proposes to construct samples by sequence with temperature trend feature-extraction, which effectively improves the overall accuracy of gyroscope. Allan variance is also utilized to verify the effectiveness of our proposed method. Lastly, this study also provides a theoretical guidance and reference for temperature error compensation in other types of sensors.
查看更多>>摘要：In this work, we have studied theoretically the dynamics of optical properties of silicon and gallium arsenide at the wavelengths near the edge of interband absorption after excitation by an intense femtosecond laser pulse. It was shown that the transmittance of a semiconductor plate should rapidly increase during electron-phonon relaxation. This effect can be used to experimentally determine the electron-phonon relaxation time for band gap materials. The optimal conditions for the experimental observation of the effect of ultrafast enlightenment of semiconductors were defined.
查看更多>>摘要：We construct two-dimensional soliton solutions for the inhomogeneous nonlinear Schrodinger (NLS) equation with power-law nonlinearity in two different types of parity-time (PT )-symmetric potentials, namely Rosen-Morse and hyperbolic Scarff-II potentials, through a similarity transformation. In each case, following three different kinds of dispersion parameters are considered: (i) exponential, (ii) periodic, and (iii) hyperbolic. We investigate the impact on the dynamical characteristics of solitons by varying the strengths of the inhomogeneity parameter. We also analyse the intensity variations of solitons at different propagation distances for three distinct dispersion profiles. Further, we observe that the intensity distribution of solitons stretches in space and that the width of it increases as the value of the power-law nonlinearity parameter increases. Our findings reveal that the obtained soliton solutions can be managed with the help of the strengths of both PT-symmetric potentials and dispersion parameters.
查看更多>>摘要：In the quest to enhance photovoltaic devices' efficiency and swift progress in the organic solar cell, community scientists are focusing on small molecules donors. The four specific donor molecules, namely TDMDN1, TDMDN2, TDMDN3, and TDMDN4, are designed from recently reported synthetic TDMDN reference molecules. The designed molecules TDMDN1-TDMDN4 have phenyl-di-p-tolyl-amine attached with different acceptors (terminal side). Quantum chemical and photovoltaic parameters of TDMDN1-TDMDN4 were estimated through DFT at MPW1PW91/6-31 G+ (d,p) . The parameters that affect the photophysical properties, exciton dynamics, chemical reactivity, and charge mobility of TDMDN1-TDMDN4 were described by calculating absorption profile, transition density matrix, frontier molecular orbit, and density of state, respectively. The result of all analyses demonstrates that TDMDN1-TDMDN4 proved more competent in executing the parameters mentioned above than TDMDN. Among all designed donors, TDMDN4 is recognized as an appropriate material for photovoltaic application due to its encouraging parameters involving reduced HOMO-LUMO energy gap (1.79 eV), lowest transition energy (1.50 eV), and highest lambda(max) value with chloroform (826 nm). The binding energy of TDMDN4 (0.29 eV) has a low value compared to the TDMDN (0.35 eV). In addition, a complex of TDMDN4 with PC61BM further verifies suitable combination. All designed donor molecules are highly recommended to attain suitable photophysical properties in solar cells and thus are proposed for the elite performance of small molecular solar cell devices.
NSTL
Elsevier