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Microstrip Antenna in IoT
Published in Praveen Kumar Malik, Planar Antennas, 2021
Arun Kumar Singh, Vikas Pandey
The geometry of the proposed graphene based Microstrip patch antenna with PBG substrate at 1.10 THz resonant frequency has been shown in Figure 18.1. The antenna has been simulated using Silicon substrate with dielectric constant/relative permittivity 11.9 having thickness of 30 µm with the antenna dimension of 100 × 100 µm2. Photonic crystal has many applications in microwave circuit, optical communication, antenna, and so forth. The Photonic Band Gap (PBG) structure is created on the substrate by drilling periodic circular cylinder. Due to non-transmission of PBG structure, it reduces the substrate absorption compared to the conventional patch antenna. Physical mechanism of photonic band gap suppresses the surface waves propagating along the surface of the substrate and reflects most of electromagnetic wave energy radiating to the substrate significantly. The dimension of the proposed antenna substrate is 100 µm × 100 µm × 30 µm.
Thermochromic and retro-reflective materials
Published in Vincenzo Costanzo, Gianpiero Evola, Luigi Marletta, Urban Heat Stress and Mitigation Solutions, 2021
Federico Rossi, Mattheos Santamouris, Samira Garshasbi, Marta Cardinali, Alessia Di Giuseppe
Photonic crystals are nano-structured materials presenting structural colours due to the interaction of light with their periodically varying refractive index components. Photonic crystals can be categorised as one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) photonic crystals. The layers thickness and refractive index are two key factors for adjusting the solar reflection of one-dimensional photonic crystals. Therefore, thermochromic one-dimensional photonic crystals can be synthesised using layers of a material capable of changing its thickness and/or refractive index by temperature. For instance, thermochromic photonic crystals can be made using alternating layers of a non-thermoresponsive (e.g. poly (dodecylglyceryl itaconate) (PDGI)) and thermoresponsive polymer materials changing their thickness with temperature (e.g. poly(acrylamide) (PAAm) and poly (acrylic acid) (PAAc)) [69]. Similarly, three-dimensional thermochromic photonic crystals can be prepared by simply modulating the particle size, refractive index, and the distance between particles. For instance, temperature-sensitive three-dimensional photonic crystals were created through self-assembly of polystyrene (PS) spheres in poly (N-isopropylacrylamide) (PNIPAM) matrix with a temperature-induced volume change feature in the temperature range between 10°C and 35°C [70]. Self-assembly strategy of colloidal photonic crystals can be considered as a cost-effective synthesis method for large-scale applications such as building application [71].
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Published in Chad A. Mirkin, Spherical Nucleic Acids, 2020
Lin Sun, Haixin Lin, Kevin L. Kohlstedt, George C. Schatz, Chad A. Mirkina
Photonic crystals have been widely studied due to their broad technological applications in lasers, sensors, optical telecommunications, and display devices. Typically, photonic crystals are periodic structures of touching dielectric materials with alternating high and low refractive indices, and to date, the variables of interest have focused primarily on crystal symmetry and the refractive indices of the constituent materials, primarily polymers and semiconductors. In contrast, finite-difference time-domain (FDTD) simulations suggest that plasmonic nanoparticle superlattices with spacer groups offer an alternative route to photonic crystals due to the controllable spacing of the nanoparticles and the high refractive index of the lattices, even far away from the plasmon frequency where losses are low. Herein, the stopband features of 13 Bravais lattices are characterized and compared, resulting in paradigm-shifting design principles for photonic crystals. Based on these design rules, a simple cubic structure with an ~130 nm lattice parameter is predicted to have a broad photonic stopband, a property confirmed by synthesizing the structure via DNA programmable assembly and characterizing it by reflectance measurements. We show through simulation that a maximum reflectance of more than 0.99 can be achieved in these plasmonic photonic crystals by optimizing the nanoparticle composition and structural parameters.
Rapid fabrication of colloidal crystal films by spin coating using polymeric particles synthesized by dispersion polymerization
Published in Particulate Science and Technology, 2023
Thi Thu Hien Nguyen, Hoai Han Nguyen, Young-Seok Kim, Young-Sang Cho
Over the past decades, colloidal crystals have been studied intensively for various applications including chemical or biosensors, electrode materials for solar cells, and catalytic supports using macroporous inverted structures (MacConaghy et al. 2014; Kim and Yi 2016; Liao et al. 2021; Karg et al. 2015; Boane et al. 2021; Stein, Li, and Denny 2008). Among them, reflective color filter using colloidal crystal can be considered as a promising application, since commercial effort has been made by industries such as Opalux and Corning (Yu et al. 2014). Due to selective reflection of visible light at specific wavelength, colloidal crystals can be used as photonic crystal, which can be applied to reflective pigment for reflective displays (Lee et al. 2013). Though lithographic approaches can be adopted for the fabrication of photonic crystal, colloidal self-assembly as bottom-up approach is more advantageous in that expensive equipment are not necessary and economic raw materials can be used for the synthesis of building block particles of colloidal crystal.
Fibre optic sensor based multi-gas detection using optimized convolutional neural network
Published in Journal of Modern Optics, 2022
R. Ganesh Babu, C. Chellaswamy, T. S. Geetha, R. Ramesh
Optical fibre gas sensors are finding increased importance in various applications that include commercial, industrial and medical. Industries such as petroleum and mining utilize this sensor in the detection of explosive/flammable gases [1,2]. The photonic crystal is a smart optical material used for manipulating and controlling the flow of light, and the refractive index (RI) in the range of nano-scale dimension can be changed. They are small in size, have wider frequency range of operation, known for lower fabrication costs, are easy integration with other optical devices, and have an optical bandgap. In general, two design methods, namely, (1) changing the RI of the air by spreading the gas (keep the dielectric rod in the air substrate) and (2) making air holes in the slab substrate are used in the operation [3,4].
An overview of HPDLC films and their applications
Published in Liquid Crystals, 2022
Katariya-Jain Anuja, Rajendra R. Deshmukh
Photonic crystals are artificial optical materials with periodic RI and dielectric structure, which controls the flow of photons, similar to the semiconductors, which controls the flow of electron. If the periodic structure of the crystal is of the order of the wavelength of visible light, propagation of some definite frequencies through the crystal is forbidden. This phenomenon is called as Photonic Band Gap (PBG). It depends on RI, structure, geometry and the periodicity of the crystal and defines optical properties of crystals such as transmission, reflection and their dependence on the light propagation direction. Out of various methods for generation of photonic crystals, holographic technique is preferred because it is switchable, precise, flexible, high resolution and exposes large area. In holographic lithography, proper adjustment of multiple beams and optimised polarisation of each beam can produce 2D and 3D periodic structures. The optimisation and adjustment of optical components, can be reduced using single device/technique such as photomask, prism or reflective element, using blue phase LC [58–60]. Multiple beams are generated from single beam either by wavefront splitting or by amplitude splitting in a linear and isotropic medium. The electric field correspond to n coherent interfering laser beams is: