Category Our new paper

Our new paper in Journal of Optik

Broadband and Strong Visible-Light Driven Photocatalytic Enhancement Utilizing Two-Dimensional Plasmonics of Au/Cu-Modified SrTiO₃ Perovskite Nanostructures

S.T. Sajjadian, K.-W.-A. Chee, R.A. Ejbarah, S.M. Hamidi, Y. Alissa, S. Sadeghi

Corresponding Author: m_hamidi@sbu.ac.ir

Abstract:

Addressing limited access to clean drinking water demands innovative solutions to energy and environmental crises. Photocatalysis offers promise without eliciting secondary pollution, yet traditional metal oxide semiconductor photocatalysts encounter impediments in solar energy utilization and charge carrier recombination rates. To overcome these limitations, we present for the first time, a novel design, fabrication, and characterization of two-dimensional plasmonic noble metal/perovskite nanostructure hybrids for photocatalysis, combining Au as the plasmonic material with Cu-modified SrTiO₃ as the semiconductor, fabricated on elastomeric polydimethylsiloxane substrates. Integrating localized surface plasmon resonance and Schottky junction-related band-bending significantly extends optical absorption into the ultraviolet-visible-infrared bands and enhances the effective carrier lifetimes, ensuring state-of-the-art photocatalytic efficiency. Exceptional photocatalytic performance in a 5-ppm aqueous methylene blue solution can be attained with 72.69-wt. % Cu incorporation in the perovskite oxide, reaching a visible light-mediated photodegradation efficiency of 26% – an astounding 62.5-% efficiency increase compared to previous experiments without Cu modification. This advancement underscores the synergistic potential of noble metals and photocatalytic semiconductors in managing water purification challenges.

Our new paper in Journal of optik

Magneto-Plasmonic-Induced Random Laser in Two-dimensional FeB Square Array

Majid F. Haddawi, J. M. Jassim, S. M. Hamidi

This work aims to enhance the lasing parameters of a random laser using magneto-plasmonic FeB@Au as scattering points. Two-dimensional FeB square arrays are covered by thin films of Rhodamine 6G from the bottom and top, respectively. For this purpose, two-dimensional structures were fabricated using the soft lithography method onto the polydimethylsiloxane (PDMS) substrate and deposited with a 35 nm thick gold layer using a sputtering machine, followed by a FeB (iron boride) thin layer using the radio frequency (RF) sputtering machine method. Finally, the samples were coated by rhodamine 6G dye. The samples were pumped via the second harmonic generation of the Nd:YAG laser under an external magnetic field set to 50 mT, and the random lasing action was measured using a spectrometer. Our results indicated a better ability to achieve random lasing under the external magnetic field. The output emission spectra increased with a decreased laser threshold from 0.66 mJ to 0.35 mJ, and the full width at half maximum (FWHM) decreased from 7.8 nm to 4 nm.

Relative Emission spectrum of samples at different pumping energies from 0.17 to 1.07 mJ and (b) Schematic diagram of the main two-dimensional substances before dye coating.

Our new paper on THz

Our new َArticle in Journal of nature

Design and analysis of a fexible Ruddlesden–Popper 2D perovskite metastructure based on symmetry‑protected THz‑bound states in the continuum

Seyedeh Bita Saadatmand, Samad Shokouhi, VahidAhmadi & Seyedeh Mehri Hamidi

A Ruddlesden–Popper 2D perovskite PEA₂PbX₄ (X= I, Br, and Cl) is proposed for metasurface applications. Density functional theory is used to analyze the optical, electrical, mechanical properties, moisture and thermodynamic stability of PEA₂PbX₄. The refractive index of PEA₂PbX₄ varies with the halides, resulting in 2.131, 1.901, and 1.842 for X= I, Br, and Cl, respectively. Mechanical properties with Voigt-Reuss-Hill approximations indicate that all three materials are fexible and ductile. Based on the calculations of formation energy and adsorption of water molecules, PEA₂PbI₄ has superior thermodynamic and moisture stability. We present a novel metasurface based on 2D-PEA₂PbI₄ and analyze symmetry protected-bound states in the continuum (sp-BIC) excitation. The proposed structure can excite multiple Fano quasi-BICs (q-BICs) with exceptionally high Q-factors. We verify the group theoretical analysis and explore the near-feld distribution and far-field scattering of q-BICs. The findings indicate that x-polarized incident waves can excite magnetic toroidal dipole electromagnetic-induced transparency-BIC and magnetic quadrupole-BIC, while y-polarized incident waves can excite electric toroidal dipole-BIC and electric quadrupole-BIC. The influence of metaatom and substrate losses, array size limitations, and fabrication tolerances are also discussed. The proposed structure can be employed for applications in the THz region, such as polarization dependent filters, bidirectional optical switches, and wearable photonic devices.

Our new paper on all-optical switches

Our new َArticle in Journal of Optical Materials

Thermo-Plasmon-assisted all-optical switches based on coupled micro-cavities

Hayder Maki Hamodi, Raad Sami Fyath, Seyedeh Mehri Hamidi

Given the major applications of optical switches in the next generation electronics, plasmon assisted all-optical switch is proposed based on plasmonic micro ring arrays covered with the graphene layer. For this purpose, we use a laser writing system to fabricate micro hole arrays and cover them by plasmonic gold thin film via sputtering machine, with chemical vapor deposition method being used to produce graphene layer. After theoretically and experimentally evaluating the plasmonic substrate, we use ellipsometric method to characterize the optical modes of the samples. Furthermore, the all-optical and gated switches response is recorded for the fabricated sample. Our results show phase delay plasmon induced switching as well as thermo-plasmonic affected benefit for the proposed switching structure in the order of 0.29 second (duty cycle). The suggested switch with its low power consumption, small size, and easier and low-cost fabrication process can open new insight into plasmon-assisted all-optical switches.

Our new paper on surface wave

Our new Article in Journal of Scientific Reports

Vectorial characterization of surface wave via one-dimensional photonic-atomic structure

M. Asadolah Salmanpour, M. Mosleh, S. M. Hamidi

Quantitative assessment of polarization properties of waves opens up the way for effective exploitation of them in many amazing applications. Tamm surface waves (TSW) that propagate on the interface of periodic dielectric media are proposed for many applications in numerous reports. The polarization state of TSW is not simply intuitive and would not be extracted from reflection spectra. Here considering orientation sensitive nature of the interaction between polarized electromagnetic wave and atom, we try to quantitatively characterize the polarization state of TSWs, excited on the surface of the 1D photonic crystal. To do this we performed direct contact between TSW and rubidium atomic gas by fabrication of a one-dimensional photonic crystal-atomic vapor cell and applied a moderate external magnetic field to create geometrical meaning and a sense of directionality to dark lines in reflection intensity.Our experimental results indicate that transition lines in the reflection spectrum of our hybrid system modify dependent on the orientation of the applied magnetic field and the transverse spin of TSW. We have used these changes to redefine the geometry of Voigt and Faraday for evanescent waves, especially Tamm surface waves. In the end, we performed simple mathematical operations on absorption spectra and extract the ratio of longitudinal and transverse electric field components of the polarization vector of TSW equal to 2/5.

Our new paper on imaging

Our new Article in Journal of experimental and theoretical physics

Robust Mouse Tissue imaging by Plasmonic random lase

Muna Lateef, Wajeha Abd Aldaim, Saddam Haddawi, Seyedeh Mehri Hamidi

Given the major applications of optical random laser in the next generation devices, tissue imaging is proposed in this article by the aid of plasmonic random laser media. For this purpose, we use Rhodamine 6G as the main gain medium and fill it by Gold nanoparticles, Graphene and the mixture of them as random laser generator under the Nd: YAG’s second harmonic and use them in the imaging of mouse tissue. For this purpose, Nd: YAG laser with the first harmonic select to produce nanoparticles for 4 minutes’ exposure times and the second harmonic of the laser practice as the pump light to collect the random lasing. In the 45-degree arm, the mouse tissue puts as the object and the transmitted random lasing after the tissue collect by spectrometer. Our results show good random laser emission at the maximum of 3.69mJ pumping power and thus resolution in the imaging recording from the tissues. This low cost laser medium can suggest to next generation of imaging systems based on the plasmonic random lasers.

Our new paper on THz

Our new Articlein Journal of experimental and theoretical physics

Improving the terahertz collection efficiency based on impedance matching in spintronic THz emitters

S. M. Hosseini, A. Sadraei Javaheri, F. Jahangiri, S. M. Hamidi, H. Latifi

We study the improvement of terahertz collection efficiency in a THz-TDS system based on a spintronic THz emitter, by exploring the effect of substrate impedance matching. This improvement is obtained by properly coupling of a hyper-hemispherical lens fabricated from suitable THz materials to a nonmagnetic (NM)/ ferromagnetic (FM)/ substrate emitter structure. The emitter is a Ni/Pt bilayer film coated on a MgO substrate. Refractive index and the dispersion properties of the substrate is adjusted according to the impedance matching conditions and consequently for the maximum terahertz detection by a photoconductive antenna (PCA). By comparing various substrates, including MgO, Al₂O₃, SiO₂, and polyethylene terephthalate (PET), our results reveal that the power of the THz radiation collected from the Ni/Pt/MgO with the hyper-hemispherical Si-lens coupler is 64.5 times larger than that from the Ni/Pt/MgO without the lens coupler. These results could be considered useful to achieve the guidelines for scaling the terahertz radiation power emitted from the spintronic THz emitter according to the employed substrate and hyper-hemispherical lens.

Fig. 1. Schematic illustration of (a) the THz-TDS experimental setup, and Full top view of a photoconductive antenna chip, as well as, extended top view of the midway placed THz dipole structure only displaying antenna length, gap distance and gap width; STE-induced THz divergence profile (b) without lens attachment as a reference and (c) with the hyper-hemispherical lens attachment on off-axis parabolic mirror; θ is considered cone angle in COMSOL simulation. (d) The dimensions of the hyper-hemispherical lens in accordance with the parameters presented in Table 2.