Photonics and Nanostructures-Fundamentals and Applications最新文献

Satellite communication systems for mounting on vehicles are commonly based on phased array antennas with electronical beam steering. In this work we develop active metasurface-based receive-transmit antenna arrays for newly deployed satellite constellation system running in Ku-band. Both receive and transmit subarrays are based on patch-antenna elements driven in circular polarization using 90^∘ hybrids. In both subarrays we optimized elements sizes and array period to have optimal ellipticity, gain, side lobe level. In electromagnetic simulations we achieved realized gain of 32.2 dBi for the Rx subarray and 33.4 dBi for the Tx subarray obtained in a broad scanning angle range from − 15^∘ to + 45^∘.

Transmission of microwaves through a composite plate containing Fe nanoparticles in an epoxyamine matrix, as well as reflection of waves from it, has been investigated. The experiments were performed at the frequencies from 26 to 38 GHz in the magnetic fields up to 12 kOe. The ferromagnetic resonance line in the composites with the weight fraction of Fe particles from 10% to 30% has been studied. The magnetic field dependence of the microwave power dissipation has been plotted. Field dependence of the transmission and reflection coefficients have been calculated, as well as qualitative, and in some cases quantitative, agreement has been obtained. The penetration depth of microwaves into the composites has been analyzed. Spectrum of the FMR has been constructed. Results of interaction of microwaves with Fe nanoparticles are discussed taking into account magnetic properties and composite structure.

The recent emergence of electromagnetic (EM) metamaterial absorbers (MAs) with exceptionally high absorption rates has captured the interest of numerous researchers. This study introduces an innovative design for a dual-band microwave absorber, inspired by metamaterial concepts. A square ring resonator, a second ring resonator with splits at each of its four corners, and a third ring resonator created by joining two I-shaped pieces make up the unit cell, which has the dimensions $25.5\times 25.5\times 2.54{\mathrm{mm}}^3$. These resonators are realized on a metal-backed FR-4 substrate, a common dielectric material found in printed circuit boards. The primary objective of this absorber's configuration is to achieve remarkable absorption peaks at 1.55 GHz and 3.3 GHz, attaining absorption levels of 99.73% and 99.41%, respectively. Notably, the design is insensitive to polarization and exhibits a broad incidence angle of up to 60°. It maintains high absorption rates of 95% for the transverse electric mode and 94% for the transverse magnetic mode. In order to optimize the suggested design, parametric studies were carried out for unit cell design by varying the split gap, loss tangent, and various types of metal. The advanced design system (ADS) software was used to assess an equivalent circuit, and the results of the CST simulation were compared with the circuit, confirming good agreement. These attributes are well-suited for efficiently absorbing signals within specific frequency ranges, catering to the demands of applications such as Global Navigation Satellite Systems (GNSS) and the pioneering 5G frequency band. Simulation and measured results of the absorber closely align with the expected performance, affirming the efficacy of the design. In essence, this solution provides an effective means of absorbing electromagnetic waves in these defined frequency ranges, rendering it highly suitable for diverse wireless communication and navigation systems.

A broadband absorber with multiple coupled diagonally sliced square rings at terahertz frequency using vanadium dioxide is proposed. The proposed structure exhibits more than 90 % absorption in the frequency range of 2.85–7.51 THz, with a relative bandwidth of 89.96 % and an absorption bandwidth of 4.66 THz. The absorptivity curve increases as vanadium dioxide conductivity rises from 200 S/m to 200,000 S/m, giving a wide range of tunability from 1.62 % to 100 % at 3.4 THz. Due to its geometrical symmetry, the proposed structure is independent of the polarization angle under normal incident plane waves. The proposed structure works for different incident angles for transverse electric (TE) mode and transverse magnetic (TM) mode with oblique incidence plane waves. The results demonstrate the broad bandwidth compared to the state-of-the-art designs within the same frequency band with potential applications in sensors, switches, tuning, and modulation in the terahertz range.

Metal–organic frameworks (MOFs) have recently emerged as a new class of scalable and low energy consumptive materials for microelectronic applications. Here, we experimentally extend the list of MOFs with memristive behavior for electronic data storage. Using 15 µm single crystals of UiO-66 located in 10 µm gap between Au contacts, we demonstrate an electronic set/reset process upon 15 kV cm⁻¹ of an electric field strength under normal conditions. Such low-energy data recording together with an endurance of more than 7 cycles for set/reset opens up prospects for the design of MOF-based electronic and opto-electronic devices.

Subwavelength-thick modulation of surface profile of a dielectric layer combined with a nanometer-thick metallic coating on it can be used for highly sensitive refractive index sensing using the concept of surface plasmon resonance. The performance efficiency of a 1D sinusoidal plasmonic grating of higher periodicity made of polymethylmethacrylate with gold coating on it is evaluated for monitoring water quality. The sinusoidal structure is fabricated by the cost-effective soft imprint lithography technique using a commercially available compact disk as master. Even though the master has a step profile, the solution-based technique aids in achieving the sinusoidal profile. The higher periodicity aids in attaining a higher sensitivity of 1533 nm/RIU at normal incidence and also provides a broad wavelength detection regime that can be controlled by the incidence angle. As the sinusoidal grating supports only the fundamental mode of the surface plasmon, it allows for more precise detection of any analyte. The optimized parameters for the structure are obtained through finite element method calculation.

We report on the experimental study the non-linear optical properties of UiO-66 metal-organic framework with high thermal and chemical stability. We demonstrate the coherent conversion of high-intensity incoming radiation into the third harmonics ranging from 450 to 600 nm. Moreover, eclipse z - scan of single UiO-66 microcrystals made it possible to determine the saturable absorption coefficient (β_eff = −1.415·10^-2 cm/GW at 515 nm and −3.865·10^-1 cm/GW at 1030 nm), thereby, bringing UiO-66 to the list of nonlinear and stable MOFs for real-life photonic applications.

Based on the phase transition properties of vanadium dioxide (VO₂), a metamaterial device is designed in this paper, which can achieve multiple switchable functions. When VO₂ is in the metallic state, the proposed device can realize broadband absorption with peak absorbance more than 90 % in the frequency range of 2.40–6.73 THz and broadband linear polarization conversion (LPC) with polarization conversion ratio (PCR) greater than 90% in the range of 1.80–4.21 THz, respectively, depending on whether the incidence of terahertz (THz) electromagnetic (EM) wave is from top side or bottom side. When VO₂ is in the insulated state, the proposed device can achieve LPC of half-reflection and half-transmission (HRHT) and transmissive linear-to-circular (LTC) polarization conversion. The study in this paper has guiding significance in the design of THz metamaterial devices with multiple functions.

Nonradiating sources and anapoles are curious objects from the physics of invisibility that illuminate subtle concepts of fundamental electrodynamics and have promising applications in nanophotonics. The present work shows that a perfectly conducting sphere with a hidden magnetic field is a simple nonradiating electromagnetic source with mechanical excitation and complete internal confinement of electromagnetic energy. It does not require external electromagnetic excitation and is excited by rotation, which induces internal charges and currents with a self-compensating external radiation. The constructed source acts on itself through Lorentz forces emerging from the interaction of charges and currents with electromagnetic fields inside the sphere and, when having a freedom of rotation about the fixed center, exhibits regular precession like a gyroscope. This self-action reveals an internal electromagnetic activity of the perfect nonradiating source, externally inactive and invisible. Neutron stars, these nanospheres of space, can be such natural nonradiating sources when their magnetic fields are buried.

Fabrication technology, which allows a substantial decrease of the plasmonic propagation loss for both “plasmon- friendly” metals like Au, Cu or Al and “plasmon- unfriendly” metals like Co, Fe or Cr, has been developed and experimentally demonstrated. Optimization of the optical confinement is used to reduce the propagation loss below 1 dB per plasmonic device.