Research Output
Articles
Publication Date: 2025
Optics Express (10944087)33(3)pp. 4550-4562
All-optical switches (AOSs) with the unique functionality of light controlling by light are the essential components of advanced photonics. However, it is still a grand challenge to propose materials with appropriate nonlinear effects and structures with high-performance all-optical switching. This study proposes an AOS with a hybrid silica-azopolymer optical microfiber coupler configuration. This structure is characterized by in-line switching functionality, extremely high extinction ratio of 22 dB at λ = 1550 nm, low-insertion loss (<1 dB), and ease of fabrication process. It is shown that, because of the photo-induced birefringence in the azopolymer microfiber, the functionality of the introduced switch depends on the polarizations of the controlling and propagating light signals. Moreover, using full-wave electromagnetic simulations, the performance of the hybrid AOS is explained and clarified. © 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
Publication Date: 2024
IEEE Sensors Journal (1530437X)24(24)pp. 40994-41002
Optical microfiber couplers (OMCs) with simple structure, low loss, and high sensitivity have been broadly involved in physicochemical fiber sensing applications. Until now, the fabrication of OMCs using arc discharge as a fast, clean, and low-cost method has not been explored. In this study, an arc-discharge fiber heating and pulling process for OMC manufacturing is presented and the characteristics of the arc-induced structures are investigated. It is shown that, in addition to high spectral visibility and refractive index (RI) sensitivity, importantly, the arc-induced OMCs exhibit ultralow temperature dependency of less than 1.9 pm/°C, over the wide testing range of 15 °C to 315 °C. Finally, an exact theoretical explanation is presented for the observed different temperature coefficients using analytical expressions and full-wave simulations based on the modal analysis of OMCs. Thus, the introduced arc-discharge technique and the resultant OMCs with ultralow temperature dependency could be useful for real-world applications of microfiber (MF) couplers. © 2001-2012 IEEE.
Publication Date: 2024
CES Transactions on Electrical Machines and Systems (20963564)8(4)pp. 404-413
In this manuscript, a new axial-flux permanent-magnet machine (AFPMM) is designed, analyzed, improved, and successfully tested. A double-sided AFPM generator with four layers of stator winding is initially designed using a well-known quasi-3D analytical method. Then, the designed machine is simulated using commercial software. It is shown that modification techniques are required to improve the performance of both the torque ripple and the ratio of the third to the fundamental harmonics of the induced voltage. Therefore, a new improvement technique is proposed, in which the layers of the stator winding are shifted relative to each other. While this new technique significantly improves the third harmonic problem, the design still has a high torque ripple and, thus, it is suggested to combine the proposed method with the conventional magnet shifting technique. It is revealed numerically that the resulting combination properly resolves both third harmonic and torque ripple problems. Therefore, this design is considered the main design of the present manuscript. In the end, a prototype of the main design is manufactured and tested. It is shown that the measurement results are in good agreement with those of numerical software.①. © 2024 CES.
Publication Date: 2024
Chemical Engineering Journal (13858947)496
Nowadays, water and energy crises are important worldwide challenges. Many efforts have been devoted to develop efficient photothermal membranes for water desalination based on membrane distillation (MD) using renewable solar energy. In the way of investigating the parameters influencing MD, photothermal membranes with different surface morphologies were prepared based on electrospinning and casting techniques by changing the relevant parameters. For this purpose, solutions containing carbon black nanoparticles were used. The long-term photothermal vacuum MD (PVMD) performance of the membranes was guaranteed by omniphobic modification of surface using low-pressure plasma polymerization of perfluorooctyl acrylate monomers. It was well demonstrated that membrane surface morphology (roughness and porosity) and its photothermal activity are linearly correlated with coefficients of determination (R2) more than 0.9. In other words, membrane with efficient PVMD performance is expected provided that the membrane surface morphology is sufficiently rough and porous to enhance light absorption and trapping and simultaneously create the lowest and highest resistance against transfer of water molecules and wetting, respectively. The membrane with designed surface morphology (average roughness of 306.7 nm and porosity of 32.6 %) exhibited the most enhanced photothermal activity with evaporation efficiency as high as 93.5 %. Reducing average surface roughness and porosity to 101.1 nm and 5 %, respectively, led to a membrane with inferior PVMD performance and low evaporation efficiency as 60.7 %. The membrane with optimal performance exhibited a permeate flux of 2.85 kg/m2·h. This membrane also provided long-term performance against wetting by the feed solution containing 0.6 mM sodium dodecyl sulfate for 540 min. © 2024 Elsevier B.V.
Publication Date: 2023
IEEE Transactions on Antennas and Propagation (15582221)71(9)pp. 7376-7386
The reflection tensor of a metafilm with bianisotropic elements on a dielectric interface is analytically derived. First, using the dipole approximation, the nanoparticles are replaced with electric and magnetic dipoles. Next, the local fields are obtained as the superposition of the background field and the interaction fields (sum of fields by all dipoles and their images). The latter is written in a form that directly results in either fast-converging series or series with closed-form solutions. Utilizing the local fields, the collective polarizability tensor and the dipole intensities are determined. Then, assuming the array to be dense, the dipole array is replaced with current sheets, for which the radiated fields in the presence of a substrate are well-known. Next, the reflection tensor is derived, validated, and discussed. Moreover, using a numerical scheme, the polarizability tensor of a bianisotropic nanoparticle in free space is calculated. Using the computed polarizability tensor and the derived analytical expressions, reflection from a metafilm with bianisotropic nanoparticles on an interface is obtained. Finally, the more complex problems of embedded particles and oblique illumination are briefly addressed. © 1963-2012 IEEE.
