Photonic Stopband Filters Based on Graphene-Pair Arrays

We investigate the photonic bandgaps in graphene-pair arrays. Graphene sheets are installed in a bulk substrate to form periodical graphene photonic crystal. The compound system approves a photonic band structure as a light impinges on it. Multiple stopbands are induced by changing the incident frequency of light. The stopbands widths and their central frequencies could be modulated through the graphene chemical potential. The number of stopbands decreases with the increase in the spatial period of graphene pairs. Otherwise, two full passbands are realized in the parameter space composed of the incident angle and the light frequency. This investigation has potentials applied in tunable multi-stopbands filters.

Dressed emitters as impurities

Dressed states forming when quantum emitters or atoms couple to a photonic bath underpin a number of phenomena and applications, in particular nonradiating effective interactions occurring within photonic bandgaps. Here, we present a compact formulation of the resolvent-based theory for calculating atom-photon dressed states built on the idea that the atom behaves as an effective impurity. This establishes an explicit connection with the standard impurity problem in condensed matter. Moreover, it allows us to formulate and settle – independently of the bath Hamiltonian – a number of properties previously known only for specific models or not entirely formalized. The framework is next extended to the case of more than one emitter, which is used to derive a general expression of dissipationless effective Hamiltonians explicitly featuring the overlap of single-emitter dressed bound states.

Extremely Low Effective Impedance in Stratified Graphene-Dielectric Metamaterials

The periodic reflections in frequency were observed in a stack of graphene layers and reported as a series of mini photonic bandgaps owing to the multiple interference by the graphene layers. In this research, the effective medium approach was employed to obtain the effective refractive index and Bloch impedance for understanding the wave propagation characteristic therein. Specifically, the pure real effective refractive index without attenuation as well as an extremely low Bloch impedance were found at the frequencies exhibiting periodic reflections. Some numerical examples were demonstrated to show that the series bandgap-like reflections in fact are attributed to considerable impedance mismatch caused by this ultra low Bloch impedance.

Photoresponsive Photonic Crystals Constructed From Azobenzene-Grafted Silica Microspheres

Azobenzene compounds have been widely used in many fields and through their response to light they can be used to regulate the properties of ordered structures. In this paper, sub-micrometer colloidal SiO2 spheres are prepared and azobenzene groups are grafted on the surface of SiO2 microspheres. The SiO2 microspheres grafted with azobenzene groups could self-assemble to form photosensitive photonic crystals (PCs), whose photonic bandgaps red-shifted as irradiated by UV light and showed good reversibility.

Design of Cold Plasma Based Ternary Photonic Crystal for Microwave Applications

In this paper, we propose a Silicon/Plasma/Air ternary 1D photonic crystal, whose transmission and reflection properties have been studied. We draw the transmittance and reflectance versus frequency spectra in microwave region (GHz) for RHP Plasma based ternary PC by changing the angle of incidence for a fixed value of unit cells, magnetic field, layer thickness, collision frequency, and electron density. It is observed that with increase in angle of incidence, there is increase in photonic bandgap obtained in low and high frequency regions. With increase in angle, the photonic bandgaps shift towards higher frequencies. At angle 89° there are multiple sharp peaks of transmission are obtained. By comparing this ternary PC with a binary silicon/plasma PC, it is observed that this proposed PC has higher number of bands for smaller angles which makes them a good candidate for making multi-channel tunable filters, and for higher angle it behaves like broadband reflector. The proposed structure may also be a good candidate for many applications in making other microwave devices.

Light-activated shape morphing and light-tracking materials using biopolymer-based programmable photonic nanostructures

Natural systems display sophisticated control of light-matter interactions at multiple length scales for light harvesting, manipulation, and management, through elaborate photonic architectures and responsive material formats. Here, we combine programmable photonic function with elastomeric material composites to generate optomechanical actuators that display controllable and tunable actuation as well as complex deformation in response to simple light illumination. The ability to topographically control photonic bandgaps allows programmable actuation of the elastomeric substrate in response to illumination. Complex three-dimensional configurations, programmable motion patterns, and phototropic movement where the material moves in response to the motion of a light source are presented. A “photonic sunflower” demonstrator device consisting of a light-tracking solar cell is also illustrated to demonstrate the utility of the material composite. The strategy presented here provides new opportunities for the future development of intelligent optomechanical systems that move with light on demand.

Computing Photonic Bandgap from Dispersion Relation for TM Mode Propagation Inside Metamaterial-Based 1D PhC

: Calculation of dispersion profile and photonic bandgap for negative refractive index based onedimensional photonic crystal structure. Objective: Determine mathematically the variation of first and second photonic bandgaps under angular incidence variation for the metamaterial-based 1D PhC structure for both TE and TM mode of propagations. Methods: Two lowermost photonic bandgap widths of metamaterial-based one-dimensional photonic crystal are analytically computed from the dispersion relation under the propagation of transverse electromagnetic wave along the direction of confinement. Three practically realizable double negative index materials are considered for computation of bandgaps, where air-gaps are considered along with the artificially made materials as the composite grating structure. This is a combination of negative positive indices materials, where incident angles are tailored within practical limit to calculate the variation of bandgaps, which may be quasi or complete depending on the material composition and angle of incidence. Results: Results are compared with that obtained for TE mode propagation, and are highly important for design of the all-optical filter with DNG materials.