查看更多>>摘要：Conventionally, the behavior of light transmission in optical devices is based on total internal reflection or photonic bandgaps. The Dirac mode is regarded as another guiding mechanism that relies on the zero-density of radiation states around the Dirac point to avoid power leakage and thus achieves field confinement. Unlike conventional light guiding mechanisms, the Dirac mode features a unique algebraic decay profile around the Dirac frequency. In this study, the Dirac mode in the Kagome lattice of photonic crystals (PCs) at a Dirac frequency that is beyond any complete photonic bandgaps is observed, and its features are verified using finite difference time domain analyses. The results indicate that the Dirac mode in the triangular, honeycomb, and two-compound lattices of PCs also occurs in the Kagome lattice and has an extremely high quality factor of 1.03 x 10(6). Furthermore, analyses of the Dirac mode serve as a convenient method to control the all-range Dirac frequency by modifying the structural parameters accordingly, thus extending the applications of the Dirac mode in modern integrated optical devices.
查看更多>>摘要：A novel method enabling the production of an ultrabroad dual-triangular filter (DTF) is proposed and numerically demonstrated, which is realized by using an optimized phase-modulated helical long-period fibre grating (PM-HLPG) operated especially at wavelengths near the dispersion-turning-point (DTP) of cladding-mode LP1,10. As a typical design example, four linearly spectral regions, each with dynamic ranges of similar to 177 nm in wavelength and similar to 82% in transmission loss, have been successfully achieved, which are the best results reported to date among all grating-based triangular filters. It is believed that the proposed DTF will find potential applications in broadband power-interrogated fibre sensing systems.
查看更多>>摘要：Metal-based nanoparticles are limited in their applications due to their inherent loss. Here, we propose all dielectric nanoparticles to enhance forward scattering efficiency. Firstly, all dielectric nanoparticles composed of lossless nanodisks are created. By changing the geometric size of the nanoparticles, 2 phase coverage can be achieved. We further coded these all-dielectric nanoparticles to construct nanoparticle coded metasurface. Then, we propose a superposition principle of super-grating coding sequence, which can control the scattering angle of coding metasurface. It is clear that theoretical results were compared with results of computer simulation. Due to the limitation of the generalized Snell's law, the forward scattering angle of the encoded nanoparticle sequence is limited to several directions. In order to obtain the multi-angle forward scattering, we introduce the addition principle of coded nanoparticle sequences. By adding and subtracting two sequences of encoded nanoparticles, a new sequence of encoded nanoparticles was obtained. Furthermore, we introduce the complex phase encoding of the coded nanoparticles sequence to construct a new multi-functional and multi-angle coded nanoparticles sequence. Based on the principle of addition of complex phase-coded sequences of nanoparticles, the continuous angle scattering and superposition of scattering beams in any direction can be expected to be obtained.
查看更多>>摘要：Deep learning has shown the high potential for the use of resolution enhancement in microscopic imaging. However, a large amount of paired datasets are usually required for training the networks. Data preparation is costly from the microscopic experiment. In this paper, the cycle generative adversarial network, trained by only a small amount of unpaired experimental microscopic images, is used to generate paired data for supervising learning in resolution enhancement. A typical network for resolution enhancement, named Pix2Pix-GAN, is then trained by the generated images to generate high-resolution images. A various of samples have been tested. From the images obtained with low-power microscopes, the trained network can output the images similar to those acquired with high-power microscopes. Results show that the generated dataset can effectively replace the experimental one for neural network training. Problems related to the experimental paired data preparation are then solved. The proposed method further broadens the application of deep learning for the optical field, especially for resolution enhancement in dynamic microscopic imaging.
查看更多>>摘要：The influencing factors and modulating effects of Fano resonance in a plasmonic metal-insulator-metal waveguide Fano system have been extensively studied in the past. While standing wave node of the electromagnetic field in the resonator in the Fano system, which can play a good and flexible regulating role in Fano resonance in its own way, has not been systematically studied. In view of the important and special influence of standing wave nodes on Fano resonance, it is necessary to be studied systematically. This study investigates a plasmonic Fano-resonance system comprising a metal-insulator-metal waveguide and stub resonator, which is side-coupled to a square-cavity resonator. The variations in the transmission properties of the system corresponding to changes in its different geometric parameters are investigated via finite-element analyses. Furthermore, the peak Fano-resonance wavelength equation deduced in this study is applied in combination with the standing-wave theory to explain the Fano-resonance phenomenon. The results obtained reveal that the effect of the nodes corresponding to the standing-wave modes (1, 0) and (1, 1) in square/rectangular cavities facilitates the remarkable and flexible regulation of Fano resonances corresponding to the said modes as the stub shifts from the horizontally self-symmetric to the self-asymmetric orientation about the vertical nodal lines. The formation mechanism of standing-wave-node adjustment in square cavity to facilitate Fano resonance is analyzed. When the stub remains horizontally self-asymmetric about the vertical nodal lines of the mode (0, 1), the first-order mode in the square cavities, which facilitates the realization of Fano resonance, is dual in nature and comprises the (0, 1) and (1, 0) modes. It is confirmed that more favorable relative positions of the stub and the square cavity result in a higher probability of realizing Fano resonance Six instances of Fano resonance of the structure comprising two single-side-coupled square cavities are realized in this study. The coupling arrangement is such that the Fano resonance remains unaffected by the standing-wave nodes in the square cavities. The proposed structure demonstrates a sensitivity of 1128 nm/RIU (RIU: refractive index unit). Furthermore, the geometric parameters are optimized considering a fixed environmental refractive index of 1.04. The resulting optimum figure of merit equals 2.76 x 10(4). The proposed plasmonic Fano system demonstrates great potential for use in micro-nano photonic integrated circuits and high-sensitivity sensors.
Karaaslan, MuharremAli, Hema O.Al-Hindawi, Asaad M.Abdulkarim, Yadgar, I...
10页
查看更多>>摘要：In this paper, we developed a new design of multiband perfect metamaterials absorber (MTMA) to be operated in the frequency range of 8-12 GHz. Proposed structure consists of a combination of three basic structures which is based on Closed Circular Ring Resonators (CCRR). A dielectric substrate is chosen as FR-4 material of 1.6 mm thickness and 22x22 mm size was used. The proposed (MTMA) operated at six different resonance frequencies 8.3 GHz, 9.2 GHz, 9.88 GHz, 10.66 GHz, 11.16 GHz, and 11.85 GHz with the absorption of 100 %, 100%, 98%, 91%, 98%, and 98% respectively. Negative parameters such as permittivity (epsilon) permeability (mu) reflective index (n), and impedance (z) were extracted and presented. Results indicated that the MTM absorber was found to extremely independent on the angles of polarization of the incident waves and the absorber was almost insensitive to the incident angle (0 degrees - 90 degrees) for transverse electric (TE) or transverse magnetic (TM) modes. The working principle of the structure is analyzed and illustrated through input impedance, surface current, and the electric field of the structure. The designed absorber was fabricated and experimentally measured in microwave laboratory that shows a good agreement with simulation results. According to the obtained results, the proposed metamaterials absorber is a good candidate for the military RADAR applications.
查看更多>>摘要：Ultra-compact multichannel optical waveguide crossings are designed by a particle swarm optimized inverse design method. The 2 x 2 TE (TM) device has an ultra-small footprint of 2 x 2 mu m(2) and exhibits a high transmission efficiency of 69.1% (89.7%) and low crosstalk of -34.4 dB (-84.8 dB) at 1550 nm. The devices can work within a large range of pixel size and waveguide width, suggesting high process tolerance of the design method. To further extend the functionality, a 3 x 3 device with the same size is designed, which exhibits a remarkable transmission efficiency of 47.6%, 61.8%, 67.2%, and low crosstalk of -33.3 dB, -39.2 dB, and -49.9 dB, respectively, for the three transmission paths. In addition, by adjusting the structure, other types of 3 x 3 devices with different transmission paths are demonstrated. The ultra-compact broad-bandwidth high-process-tolerance optical waveguide crossings have great potential in high-integration photonic-integrated circuits.
查看更多>>摘要：With the aim of improving UV light trapping capability in monolayer graphene, a nanomesh metamaterial absorber is proposed, which exhibits the polarization-insensitive feature due to the geometrical symmetry. Through the functional combination of magnetic resonance and UV mirror, the absorption of unpolarized UV light in monolayer graphene can reach 99.5% under normal incidence. The absorption enhancement is induced by the magnetic resonance mode between the dielectric silica nanomesh and the calcium fluoride base layer. The effects of geometric parameters on the absorption spectra are systematically investigated. The proposed structure shows insensitive to manufacturing deviations, which can maintain at a high UV absorption rate of more than 99% within the nanomesh width ranging from 50 nm to 90 nm. Furthermore, after delicate optimization of the geometric parameters, two sharp resonances with absorbance more than 90% can be excited simultaneously inside the absorber. Our work provides an important theoretical guide for the design of optoelectronic devices based on two-dimensional materials in the UV range.
查看更多>>摘要：In this study, we propose a compact four-channel angular-multiplexing polarisation holographic microscope to quantify the spatially resolved Jones matrix of a dynamic sample in a microfluidic channel. To make the imaging system compact, a common-path off-axis configuration based on a simple object and a reference beam generator unit, consisting of a Wollaston prism and a converging lens, was introduced in the holographic microscope. Using this system and the retrieval method described in this paper, the spatially resolved Jones matrix parameters, as well as the polarisation information, including the diattenuation and phase retardation, of the target sample could be simultaneously retrieved from a single-shot hologram. We experimentally demonstrated the feasibility of our method by quantitatively measuring the birefringence parameters of a quarter-wave plate and extracting the 2-D Jones matrix and polarisation parameters of potato starch particles and C. elegans worms. The simple optical structure and common-path design reduce the system requirements for light source coherence and system stability, which provides a feasible approach for the development of a for microfluidics.
查看更多>>摘要：We study the polarisation properties of random N x N scattering matrices distributed according to the circular orthogonal ensemble. We interpret 2 x 2 sub-blocks of the scattering matrix as Jones matrices and study their statistical properties. Using the polar decomposition, we derive probability density functions for retardance and diattenuation from scattering matrices of arbitrary size and in the limit N -> infinity.
NSTL
Elsevier