Omnidirectional Photonic Band Gap in One-Dimensional Ternary Superconductor-Dielectric Photonic Crystals Based on a New Thue–Morse Aperiodic Structure

In this paper, an omnidirectional photonic band gap (OBG) of one-dimensional (1D) ternary superconductor-dielectric photonic crystals (SDPCs) based on a new Thue–Mores aperiodic structure is theoretically studied by the transfer matrix method (TMM) in detail. Compared to zero- $\bar{n}$ gap or single negative (negative permittivity or negative permeability) gap, such OBG originates from Bragg gap. From the numerical results, the bandwidth and central frequency of OBG can be notably enlarged by manipulating the thicknesses of superconductor and dielectric layers but cease to change with increasing the Thue–Mores order. The OBG also can be tuned by the ambient temperature of the system especially close to the critical temperature. However, the damping coefficient of the superconductor layer has no effects on the OBG. The relative bandwidth of OBG also is investigated by the parameters as mentioned above. It is clear that such 1D ternary SDPCs have a superior feature in the enhancement of the bandwidth of OBG compared to the conventional ternary SDPCs and conventional ternary Thue–Mores aperiodic SDPCs. These results may provide theoretical instructions to design the future SDPCs devices.     

Photonic band gap structures by sol–gel processing

Since the launching of the photonic bandgap concept in 1987, the development of corresponding structures has expanded very rapidly, in particular two-dimensional semiconductor-based structures. In the case of sol–gel derived materials, the main emphasis for the past year has been on one-dimensional multilayer stacks and, in particular, on three-dimensional structures of the opal and inverse opal type.     

Photonic crystalline IR fibers for the spectral range of 2-40 μm

Monocrystals of Ag(1-x)Tl(x)Br(1-x)I(x) and Ag(1-x)Tl(x)Cl(y)I(z)Br(1-y-z) for the spectral range from 2.0 to 40.0 μm with improved photostability were developed and grown. The grown crystals were used for fabrication of single-mode IR fibers. Experimental studies of optical properties of these fibers have confirmed their single-mode operation at CO2 laser wavelength and demonstrated wider mode field for microstructured fiber compared to fibers with conventional double-layered structure.     

Broadening of Photonic Band Gap in a One—Dimensional Superconductor Star Waveguide Structure

The present paper describes the theoretical investigation of enlarged reflection bands (photonic band gaps) in a 1D star waveguide (SWG) structure consists of superconductor and dielectric as its constituent materials. For the present study, we take the different combinations of superconductor and dielectric materials as a backbone and side branches of the SWG structure. In order to obtain the dispersion relation, Interface Response Theory (IRT) has been employed. Photonic band gaps of SWG structure having superconductor?Csuperconductor, superconductor?Cdielectric, and dielectric?Csuperconductor materials are compared with the band gaps of the conventional photonic crystal (PC) structure having superconductor?Csuperconductor and dielectric?Csuperconductor materials. Analysis of the dispersion characteristics shows that there exists no band gaps for conventional PC when both layers are made of the same superconducting materials (as the usual case) while the SWG structure shows forbidden bands of finite width even the backbone and side branches are made of same materials. Also, the SWG structure having superconductor?Cdielectric shows the wider reflection bands in comparison with the structure having dielectric?Csuperconductor as its constituent materials, while for the conventional PC structure it is same in both the cases. Further, the effect of temperature and the effect of variation of number of grafted branches on the photonic bands of SWG structure have been studied.     

Photonic Fractal Metamaterials: A Metal–Semiconductor Platform with Enhanced Volatile-Compound Sensing Performance

Advance of photonics media is restrained by the lack of structuring techniques for the 3D fabrication of active materials with long-range periodicity. A methodology is reported for the engineering of tunable resonant photonic media with thickness exceeding the plasmonic near-field enhancement region by more than two orders of magnitude. The media architecture consists of a stochastically ordered distribution of plasmonic nanocrystals in a fractal scaffold of high-index semiconductors. This plasmonic-semiconductor fractal media supports the propagation of surface plasmons with drastically enhanced intensity over multiple length scales, overcoming the 2D limitations of established metasurface technologies. The fractal media are used for the fabrication of plasmonic optical gas sensors, achieving a limit of detection of 0.01 vol% at room temperature and sensitivity up to 1.9 nm vol%⁻¹, demonstrating almost a fivefold increase with respect to an optimized planar geometry. Beneficially to their implementation, the self-assembly mechanism of this fractal architecture allows fabrication of micrometer-thick media over surfaces of several square centimeters in a few seconds. The designable optical features and intrinsic scalability of these photonic fractal metamaterials provide ample opportunities for applications, bridging across transformation optics, sensing, and light harvesting.     

High-Performance Nonvolatile Organic Photonic Transistor Memory Devices using Conjugated Rod–Coil Materials as a Floating Gate

A novel approach for using conjugated rod–coil materials as a floating gate in the fabrication of nonvolatile photonic transistor memory devices, consisting of n-type Sol-PDI and p-type C10-DNTT, is presented. Sol-PDI and C10-DNTT are used as dual functions of charge-trapping (conjugated rod) and tunneling (insulating coil), while n-type BPE-PDI and p-type DNTT are employed as the corresponding transporting layers. By using the same conjugated rod in the memory layer and transporting channel with a self-assembled structure, both n-type and p-type memory devices exhibit a fast response, a high current contrast between “Photo-On” and “Electrical-Off” bistable states over 10⁵, and an extremely low programing driving force of 0.1 V. The fabricated photon-driven memory devices exhibit a quick response to different wavelengths of light and a broadband light response that highlight their promising potential for light-recorder and synaptic device applications.     

YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7−<Emphasis Type="Italic">x</Emphasis></Subscript>/BaTiO<Subscript>3</Subscript> 1D Superconducting Photonic Crystal with Tunable Broadband Response in the Visible Range

Based on the transfer matrix method, we studied theoretically the transmittance of a 1D photonic crystal (PC), consisting of alternating layers of a dielectric material (BaTiO₃) and a superconductor (YBa₂Cu₃O_7?x ). The dielectric properties of this system are described by the two fluid model. We have investigated the transmittance intensity and its bandwidth dependence on the superconductor thickness, incident angle, and temperature in the PC. It was found that the electromagnetic wave propagation can be controlled to be forbidden or allowed in certain wavelengths in the visible and ultraviolet range, and the photonic band gap (PBG) width can also be tuned varying these parameters. We showed that by increasing the thickness of the superconductor layer it is possible to control the number of PBGs in the structure. Also, we found that the frequency ranges of PBGs are sensitive to the incident angle and the polarization of the electromagnetic waves; the bandwidth of PBGs can be notably enlarged by increasing the angle in the TE polarization, but narrowed in the TM one. Additionally, we found that transmission is not markedly affected by temperature variation, but small shifts in the PBGs are presented. We hope these results can be of technical use for developing potential applications in optoelectronic devices.