Photonics and Nanostructures-Fundamentals and Applications最新文献

Metasurfaces have become a fascinating framework for nonlinear optics, with the advantages of a compact footprint and unprecedented flexibility to manipulate light. However, further advancements are necessary to enhance the efficiency of metasurfaces in nonlinear devices. Here, a novel approach for second harmonic generation (SHG) based on the LiNbO₃ metasurface using leaked plasmonic bound states in the continuum (BIC) is proposed. The behavior of SHG in the guided mode resonance (GMR) under TE polarization and plasmonic modes under TM polarization is investigated. The structure consists of a plasmonic grating overlying a nonlinear lithium niobate dielectric waveguide layer that supports two different BIC, namely plasmonic BIC and GMR BIC. The evolution of second harmonics generation(SHG) near two groups of BIC is explored. The SHG of the plasmonic quasi-BIC is stronger than that based on the GMR quasi-BIC. In addition, the plasmonic accidental quasi-BIC produces stronger harmonic effects than the quasi-BIC based on symmetry-broken. Specifically, at a pump intensity of 30 MW/cm², this accidental quasi-BIC results in SHG efficiency of 1.86 × 10⁻³. This work provides a valuable approach to achieving enhanced SHG using plasmonic and BIC. It opens up new possibilities for the utilization of LiNbO₃ in integrated nonlinear nanophotonics and paves the way for the development of advanced nonlinear photonic devices.

The paper introduces a 2D square lattice phononic crystal structure, with a nylon matrix and molybdenum rods as inclusions. Initially, a new type of resonator, called a triangle resonator, was designed, each of which acts as a two-input acoustic XOR logic gate. Then, a four-input acoustic XOR logic gate is presented by combining these resonators. Simulation results indicate that the realization of two-input and four-input acoustic XOR logic gates is possible using the structures we have proposed. In order to analyze the proposed acoustic XOR logic gates, the transmission spectrum is calculated using the finite element method (FEM).

The use of green-synthesized Fe₃O₄/Ag composites nanoparticles (NPs) on the surface plasmon resonance (SPR) system induced by the electric field generates the effect of electrooptic-localized surface plasmon resonance (EO-LSPR). EO-LSPR is the promising method to increase dispersibility, generate plasmons, bind to biomolecular targets, modify the refractive index, and increase the SPR signal. Green synthesis of Fe₃O₄/Ag NPs has several advantages, including being environmentally friendly, cost-effective, and sustainable. This research successfully investigated the EO-LSPR properties of green-synthesized Fe₃O₄/Ag NPs with various Ag concentrations. Green synthesis of Fe₃O₄/Ag composites NPs was prepared utilizing Moringa oleifera by an aqueous solution method. The EO-LSPR phenomenon was investigated by applying various voltages in the Kretschmann configuration with a layer arrangement of a prism/Au thin film/NPs/air with a wavelength of 632.8 nm. Transmission electron microscope results show that the average size of Fe₃O₄/Ag particles is around 16.72 ± 7.30 nm. The scanning electron microscopy-energy dispersive x-ray results showed that Ag was distributed on the surface of Fe₃O₄. The addition of Ag concentration decreased the saturation magnetization while the coercivity field increased. The SPR angle of the prism/Au thin film/air layer structures is 44.66°. After depositing with Fe₃O₄/Ag with an Ag concentration of 60 millimolar, the LSPR angle shifted by 0.98°. Under an electric field, the LSPR angle shifted to 1.00°, 1.17°, and 1.22° of 2 volts, 4 volts, and 6 volts, respectively. The results show that applying the electric field induces the LSPR angle of Fe₃O₄/Ag NPs to shift to a larger angle. Applying an electric field causes a change in the material's refractive index. The greater the applied electric field, the more significant the LSPR angle shifts. The significant shifts in the LSPR angle due to the application of an electric field indicate that the EO-LSPR system using green-synthesized Fe₃O₄/Ag composites NPs could be a promising alternative to increase the performance of SPR biosensors in the future.

In this work, we briefly review the development and status of interband cascade lasers (ICLs) as related to long-standing issues due to the InAs/AlSb superlattice cladding. By focusing on a hybrid cladding approach to alleviate these issues, we demonstrate substantially improved device performance of ICLs compared to earlier reported ICLs of a similar design in the 3–4 µm wavelength region. These improvements include a threshold current density for broad-area devices as low as 134 A/cm² at 300 K and reduced threshold voltage with a peak voltage efficiency of 80%, which is more than 10% higher than that obtained from previously reported ICLs. Moreover, we have demonstrated continuous wave (cw) operation of a broad-area device up to 278 K, the highest cw operating temperature among epi-side up mounted broad-area type-II ICLs, implying improved thermal dissipation with the hybrid cladding approach. Additionally, by conducting a comparative study of ICLs with different GaSb layer thicknesses in the hole injector, we reveal and discuss an interesting correlation between the carrier transport, threshold voltage, and hole-induced absorption loss, which may help to guide device optimization for operation in a targeted temperature range.

Nonlinear response of a nano-structure including two square quantum dots (QDs) of identical material but dissimilar sizes is discussed by considering possible quantum interferences. Density matrix approach is developed to extract physical characteristics of the system by considering Hamiltonians including couplings of the excitons to thermal bath and the possible intra-dot relaxations as well as the near field optical energy transfers (of Yukawa-type potentials) between the probable eight quantum states in subwavelength range. Realization of nonlinear behavior is studied systematically by putting the structure inside a unidirectional ring cavity and driving it by pair of dichromatic fields, that one provides a weak probe, while the other offers a strong driving component. It is shown that the absorption/dispersion properties of the probe field might be controlled by tuning the quantum interference via changing the structural features as well as the externally controlled parameters. Thus adjusting the optical bistability (OB) threshold, hysteresis cycle size or even transition from OB to multi-stability might be possible easily. Moreover, machine learning approach is proposed to evaluate how predictable are the responses of the suggested structure in various preliminary circumstances. Results clearly reflect high potential of the suggested structure for applications such as all-optical switches or memories.

A new design for a 5G millimeter-wave array antenna that is only 2.8 mm wide, using multi-stacked high-temperature ceramic substrates, is proposed in this paper. The antenna is designed to meet the requirements for esthetically pleasing and ergonomic smartphone designs and efficient component installations. To overcome challenges posed by the high relative permittivity and dielectric loss tangent of the ceramic substrates, the authors use a polymer adhesion layer with an air cavity and U-shaped probe feeding structures. The resulting 1 × 5 ceramic array antenna has a −10 dB impedance bandwidth in the low-band range of 24.25–28.35 GHz and the high-band range of 37–40 GHz, which covers the 5G New Radio frequency ranges n258, n260, and n261.

In this work, two orthogonally polarized femtosecond laser beams are employed to irradiate a p-doped silicon wafer with an electrical resistivity of 0.008 Ω·cm. It is interesting to find that 2D compound structures composed of sub-wavelength periodic ripples and deep sub-wavelength nanodot array can be produced when proper laser fluence and time delay between the dual laser beams are used. The formation of the periodic ripples can be explained by the interference between the preceding incident laser and it induced surface plasmon polaritons (SPPs). The periodic nanodot array has a period down to ∼200 nm and the radius of the nanodot is ∼30 nm, most of which appear at the boundary between the ditch and ridge of the ripple. During the ripples’ formation, the residual melting silicon is most probably located at the boundary between the ditch and ridge of the ripple. Furthermore, the period of the nanodot array is roughly equal to the perimeter of the nanodot. Therefore, it is considered that the dot array may be generated due to the Rayleigh-Taylor instability of the melting silicon. It is also noted that these nanodots are all uniformly arranged along vertical lines, indicating that the subsequent incident laser may break the stochastic characteristic of the Rayleigh-Taylor instability and produce the 2D periodic dot array. The thermo-hydrodynamical process combined with the interference effect between SPPs and the incident laser can benefit the formation of complex surface structures with versatile functions.

A dual-core photonic crystal fiber sensor based on surface plasmon resonance is theoretically proposed for the high-sensitive detection of high refractive index liquid analytes. Dual-core construction can effectively enhance the coupling effect between the fiber-core mode and the surface plasmon polariton modes, leading to sharp loss peaks at the resonance wavelengths. As the refractive index of the targeted analyte varies, the resonance condition will change as well and cause a certain shift of loss peak. Numeric results show that this dual-core fiber sensor exhibits an average linear sensitivity 9538 nm/RIU and a maximum sensitivity is 11400 nm/RIU with a resolution 8.77 × 10⁻⁶ RIU. The detected range is broad and covers the high refractive index range from 1.45 to 1.58 with an average figure of merit 284.5 RIU⁻¹. The dependence of structure parameters and the thickness of coated-metal thin-film on sensing performance is performed systemically and suggests different responses. The proposed sensor is highly promising in detecting high refractive index liquid analytes in the fields of biological detection, environmental monitoring and chemical analysis.

A new picture of the photonic eigenmodes of dielectric rings with a rectangular cross section is presented, which is fundamentally different from those of whispering gallery modes of the disc. The low-frequency photonic spectrum is formed by two types of galleries: one type begins with radial Fabry-Pérot-like resonances, and the other with axial Fabry-Pérot-like resonances, in both cases the galleries continue with a set of equidistant longitudinal modes. The new results are: (1) a linear dependence of the wavelength of radial and axial Fabry-Pérot-like resonances on the width or height of the ring, respectively, has been demonstrated; (2) it is established that all longitudinal resonances follow the spectral shifts of the corresponding Fabry-Pérot-like resonances when the width or height of the ring changes, i.e. each gallery is a separate photonic package. As a result, galleries can intersect in parametric space, leading to impressive resonance effects, including bound states in the continuum. The analysis is based on numerical calculations and experiments in near- and far-fields. Our results open the door to new fundamental phenomena and enhanced functionality of dielectric ring resonators.

With the development of society, water pollution is becoming more and more serious, especially dyeing wastewater. Fe-doped TiO₂ nano-photocatalyst was prepared by hydrothermal method. The crystal structure, morphology, optical properties, band gap width (Eg) and photocatalytic properties of the synthesized nanoparticles were characterized by XRD, SEM, TEM, EDS, XPS, FT-IR and UV–vis. The results show that Fe-TiO₂ is a mixed crystal form of rutile type and anatase type, the average crystal diameter of anatase type is 11 nm, and the diameter of rutile type is 10–50 nm. The addition of Fe can effectively reduce the band gap width of TiO₂ from 3.22 eV to 2.33 eV, so as to expand the visible light absorption range. Under 350 W xenon lamp irradiation, the degradation rate of Rhodamine B (RhB) reached 95.3% with 2% Fe-TiO₂ nanoparticles in the synergistic effect of sodium persulfate (PS) for 40 min, and the nanoparticles had good reusability. Free radical quenching experiments showed that·OH, SO₄^-·, e^-, and h⁺ pairs favored RhB degradation. The addition of Fe can form additional energy levels in TiO₂, so that the smaller energy photons can excite the electrons and holes trapped in the additional energy levels, so that the absorption of TiO₂ is redshifted and the visible light absorption range is extended. Meanwhile, PS accelerates the transformation between Fe(Ⅲ) and Fe(Ⅱ), thereby effectively improving the photocatalytic efficiency.