Optical and Quantum Electronics最新文献

The optical properties of semiconductor nanostructured systems have attracted significant interest due to their implications in fundamental physics and their potential applications in optoelectronic devices. In particular, quantum dots-nowadays synthesized experimentally with high quality-have been employed in technologies such as quantum-dot solar cells, quantum information systems, and bioimaging applications. Among the various possible quantum-dot heterostructures, our focus is on III–V semiconductors, specifically spheroidal GaAs/AlGaAs multiple-shell quantum dots. In this paper, we report the computational determination of the absorption coefficient for different quantum-dot shapes, analyzing their behavior under externally applied electric and magnetic fields. Our main finding is that quantum-dot shape deformation significantly modifies the optoelectronic properties, which can later be finely tuned using external fields. The chosen system sizes, which lie within the experimental regime, result in an optical response suitable for intraband transitions in the terahertz range of the electromagnetic spectrum.

Ga_0.997B_0.003Se single crystals were synthesized by the horizontal Bridgman method and investigated for ultrafast optoelectronic applications. X-ray diffraction confirmed the formation of a single-phase ε-GaSe structure (space group P6₃/mmc) without secondary phases. The diffraction peaks shifted slightly toward higher 2θ values due to lattice compression caused by the substitution of smaller boron atoms for gallium, while the average crystalline size (~ 84.6 nm) indicated high structural quality. The crystal exhibited p-type conductivity with a resistivity of 9.1 × 10⁶ Ω cm at 300 K and an activation energy of 1.77 eV, confirming the presence of boron-induced shallow acceptor levels about 0.25 eV above the valence band. Photocurrent spectra showed a main peak at 2.02 eV at 205 K and a redshifted maximum at 1.77 eV at 295 K, evidencing temperature-activated acceptor transitions. Time-resolved photocurrent measurements revealed an ultrafast carrier relaxation time of ~ 4 ns. Optical analysis showed a direct allowed transition with a band gap of 1.963 eV, slightly lower than that of undoped GaSe (2.02 eV). The results demonstrate that boron incorporation enhances carrier transport and response speed, making Ga_0.997B_0.003Se a promising material for high-frequency photodetectors and optical wireless communication systems.

This paper analyses progress in zinc oxide (ZnO)-based photodetectors (PDs), emphasising doping and surface passivation methods. ZnO, a wide bandgap semiconductor, has garnered interest for ultraviolet (UV) and visible light detection owing to its remarkable optoelectronic characteristics. Nonetheless, performance constraints stem from surface imperfections and charge carrier recombination. This review examines the effects of transition metal doping (e.g., Ti, Al, Ni, Cu) and co-doping (e.g., Ag, F) on the enhancement of electronic characteristics, the mitigation of defect-induced recombination, and the stabilisation of device performance. Furthermore, surface engineering methods, such as passivation layers (e.g., Al₂O₃, SiO₂) and plasmonic improvements utilising metal nanoparticles, are analysed for their impact on enhancing light absorption and charge carrier dynamics. The discussion encompasses the possibility of piezo-phototronic phenomena in ZnO-based nanostructures, emphasising their impact on photodetector efficacy. Despite obstacles in attaining defect-free structures, the incorporation of sophisticated doping and passivation methods offers considerable prospects for the creation of cost-effective, high-performance ZnO-based photodetectors.

The pursuit of non-toxic and sustainable photovoltaic materials has driven growing interest in double perovskite halides as promising alternatives to conventional lead-based absorbers. In this study, a comprehensive design, simulation, and machine learning (ML)-based optimization of lead-free K₂AMoI₆ (A = Na, Rb) perovskite solar cells has been presented. The impact of A-site cation substitution on structural and optoelectronic properties was systematically analyzed to elucidate its influence on device performance. The Na-based perovskite (K₂NaMoI₆) exhibits a relatively wider bandgap and superior open-circuit voltage, whereas the Rb-based analogue (K₂RbMoI₆) shows improved carrier mobility attributed to enhanced orbital interactions. Device simulations conducted in SCAPS-1D optimized absorber thickness, defect density, and doping concentration for both configurations. Experimental validation revealed that K₂NaMoI₆ achieved a higher power conversion efficiency (21.6%) compared to K₂RbMoI₆ (11.6%), demonstrating its superior photovoltaic potential. Additionally, the ML regression model effectively predicted device performance with an accuracy of 89.35% and 88.47% for Na- and Rb-based systems, respectively, confirming the robustness of the computational approach. Overall, these results highlight K₂NaMoI₆ as a stable, lead-free double perovskite absorber with promising efficiency and scalability for next-generation environmentally sustainable solar cells.

We introduce a generalized atomic system of N-level ((N-2)) V-configuration atom, with integer (N>2), interacting with a single mode field in the presence of multi-photon transitions and Kerr medium. We solve this system by virtue of supersymmetric (SUSY) unitary transformation and show that it possesses SUSY structure and define its SUSY generators and perform the diagonalization of the corresponding Hamiltonian. We construct the eigenstates and eigenvalues of this system when the atom and the field mode are initially prepared in two different cases. We investigate some quantum aspects of the considered system, namely, the time evolution of the atomic population inversion of the system, the evolution of the Mandel M-parameter and the distribution Husimi Q-function of the field. We show the influence of the detuning and Kerr medium parameters on their behavior for some different N, where e.g., for (N=5) we obtain the results of the five-level triple V-type system. We end with some discussions and conclusion.

In this paper, two novel ultra-high gain circularly polarized (CP) antenna structures have been proposed for drone jamming applications. One of the structures is fed with rectangular waveguide and vertical microstrip feed based on the Fabry-Perot Cavity Resonator principle, using an elliptical-shaped air cavity at the bottom of the Cylindrical Dielectric Resonator Antennas (CDRA), providing gain of 29 dBi and 99% efficiency, which is the highest in passive CDRA to the author’s knowledge. The other structure of the CDRA is built using four metasurface cells placed at a (lambda )/4 distance along the periphery. Due to this novel structure, a gain of 7.513 dBi is achieved at a frequency of 2.4 GHz. CP is achieved due to Z-shape on the ground plane in this structure. Both antennas are validated using CST simulation software and Al(_{2})O(_{3}) ceramic prototype CDRAs. The measured and simulated results are found to perfectly match each other.

1.76 μm on-chip gain features of Tm³⁺-doped LNOI(LiNbO₃-on-insulator) photonic wire are studied in case of in-band pumping at 1.66 μm wavelength. A quasi-two-level model of Tm³⁺ is proposed and validated by simulating a conventional Ti-diffused Tm:LiNbO₃(Ti:Tm:LN) waveguide amplifier and comparing with previously reported experimental result. Based on steady rate equations, analytical expressions were derived for population densities of two states involved. Important performance specifications, including population inversion, signal gain and threshold pump power, are quantified against propagation length, pump level, input signal power and Tm³⁺ concentration. Owing to ultra-compact mode field, the Tm³⁺-doped LNOI photonic wire shows much superior gain features than the conventional Ti:Tm:LN waveguide. These include much stronger pump power and propagation distance dependences of signal gain, one more orders of magnitude lower threshold pump power, and two orders of magnitude higher saturation gain. Moreover, due to absence of upconversion emissions and simultaneous single-mode operation of both pump and signal waves, the change of pumping wavelength from 795 nm to 1.66 μm results in an increase of maximal gain by nearly one order of magnitude, a decrease of optimal photonic wire length by > 35% and a decrease of threshold pump power by at least two times. Important issues related to device’s fabrication, performance and application have been clarified.

This quantum mechanical study has focused on designing thirteen hole transport materials (HTMs) based on five-membered imidazole (IM) ring for perovskite solar cells (PSCs) to discover optoelectronic properties by enhanced charge mobility for PSCs. The HTMs included an imidazole ring attached to two p-OCH₃-C₆H₅ moieties and one phenyl ring that was functionalized by neutral (H), electron-donating (Me, OMe) and electron-withdrawing groups (COOH, NO₂) in ortho, meta, and para positions. Using density functional theory (DFT) and Marcus hopping model, electronic, optical, structural, hole mobility, and photovoltaic properties were calculated for the designed HTMs. Among all molecules, meta-substituted HTMs illustrated the highest hole mobility accompanied by great photovoltaic parameters. Finally, this work established that all IM-based samples substituted by varied neutral, electron donor, and electron acceptor moieties (predominantly the meta-substituted structures) could be very efficient HTMs for the PSC photovoltaics.

A comprehensive investigation and optimization of the sensing performance for a novel hybrid apodized fiber Bragg grating (HA-FBG) have been carried out. The hybrid apodization profiles are employed to create a distinct notch in the Bragg reflectance spectrum, which is designated as the sensing signal. This approach replaces the traditional method of using the entire reflection spectrum as a sensing signal. It is observed that the sensitivity of the HA-FBG remains similar to that of the single apodization profiles; however, significant improvements are noted in detection accuracy and the quality parameter. These improvements are attributed to the substantial reduction in the full width at half maximum of the sensing signal. The comprehensive analysis underscores the superior sensing performance of Sine-Welch HA-FBGs across all investigated scenarios. Remarkably, the Sine-Welch HA-FBG yields impressive results, achieving a maximum sensitivity of 190.75 nm/RIU, a detection accuracy of 72222.23, and a quality parameter of 8919.04/RIU. These simulation findings underscore the compelling advantages of the Sine-Welch HA-FBG in all considered cases, positioning it as the optimal choice for maximizing sensing performance.

This review explores the synthesis, characterization, and potential applications of graphene, a two-dimensional material with exceptional properties. Graphene’s versatility in energy and electronics applications is highlighted, with its high conductivity and huge surface area facilitating improved energy storage capabilities in supercapacitors and batteries. In electronics, graphene is revolutionizing the industry by enabling the development of flexible displays, high-speed transistors, and enhanced thermal management systems. The integration of graphene into composite materials presents opportunities for stronger, lighter, and more conductive materials. The study provides a comprehensive overview of graphene’s current and future impact on technology, emphasizing its transformative potential in energy solutions and electronic advancements. In the energy sector, the integration of graphene into batteries, energy storage systems, capacitors, fuel cells, and renewable energy technologies marks a significant leap forward in efficiency, capacity, and sustainability. In the electronics sector, graphene’s unique characteristics are utilized in RFID, sensors, and EMI shielding, resulting in advancements in communication, security, and device miniaturization. The study underscores graphene’s potential to spearhead future innovations, reinforcing its status as a pivotal material in the ongoing technological evolution.