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Photonic quasi-crystal terahertz lasers.

ABSTRACT: Quasi-crystal structures do not present a full spatial periodicity but are nevertheless constructed starting from deterministic generation rules. When made of different dielectric materials, they often possess fascinating optical properties, which lie between those of periodic photonic crystals and those of a random arrangement of scatterers. Indeed, they can support extended band-like states with pseudogaps in the energy spectrum, but lacking translational invariance, they also intrinsically feature a pattern of 'defects', which can give rise to critically localized modes confined in space, similar to Anderson modes in random structures. If used as laser resonators, photonic quasi-crystals open up design possibilities that are simply not possible in a conventional periodic photonic crystal. In this letter, we exploit the concept of a 2D photonic quasi crystal in an electrically injected laser; specifically, we pattern the top surface of a terahertz quantum-cascade laser with a Penrose tiling of pentagonal rotational symmetry, reaching 0.1-0.2% wall-plug efficiencies and 65?mW peak output powers with characteristic surface-emitting conical beam profiles, result of the rich quasi-crystal Fourier spectrum.

SUBMITTER: Vitiello MS

PROVIDER: S-EPMC4284629 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Photonic quasi-crystal terahertz lasers.

Vitiello Miriam Serena MS Nobile Michele M Ronzani Alberto A Tredicucci Alessandro A Castellano Fabrizio F Talora Valerio V Li Lianhe L Linfield Edmund H EH Davies A Giles AG

Nature communications 20141219

Quasi-crystal structures do not present a full spatial periodicity but are nevertheless constructed starting from deterministic generation rules. When made of different dielectric materials, they often possess fascinating optical properties, which lie between those of periodic photonic crystals and those of a random arrangement of scatterers. Indeed, they can support extended band-like states with pseudogaps in the energy spectrum, but lacking translational invariance, they also intrinsically fe ...[more]

PMID: 25523102

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Project description:In recent decades, advances in biophotonics research have led to the development of numerous novel applications, particularly in the realm of diagnostic tools. Among these, one-dimensional photonic crystal biosensors have emerged as frequently utilized instruments for disease diagnosis and sensing. A significant body of research has focused on enhancing the efficiency of these biosensors. Recently, integration of Graphene and liquid crystal into a hybrid structure has been identified as a promising approach for the advancement of optical devices. This study presents a novel one-dimensional photonic crystal biosensor designed using the Kretschmann configuration, which incorporates Graphene nanolayers and a liquid crystal layer. The transfer matrix method was employed to calculate the projected band structure of the designed biosensor for different chemical potentials of the Graphene nanolayers. Additionally, the dispersion properties of the surface waves can be tuned by adjusting the liquid crystal director angle. By manipulating the adjustable parameters of the Graphene nanolayer and liquid crystal, modifications to the reflection spectrum can be achieved, facilitating an analysis of angular sensitivity and figure of merit. The results indicate that these parameters significantly influence sensitivity and figure of merit of the biosensor. Notably, increases in the chemical potential of the Graphene nanolayers, along with adjustments to the liquid crystal director angle, substantially enhance the performance of the biosensor. Our study achieved a maximum sensitivity of [Formula: see text] at a graphene chemical potential of [Formula: see text] and a liquid crystal orientation angle of [Formula: see text]. Additionally, a maximum figure of merit of [Formula: see text] was obtained at a chemical potential of [Formula: see text] and an orientation angle of [Formula: see text]. The proposed sensor is deemed suitable for practical applications due to its straightforward fabrication process and capability to operate at room temperature. Moreover, the properties of both the Graphene nanolayers and the liquid crystal layer in the biosensor can be readily adjusted, further contributing to its versatility and efficacy.

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Photonic quasi-crystal terahertz lasers.

Publications

Photonic quasi-crystal terahertz lasers.

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