scholarly journals Enhanced absorption and electrical modulation of graphene based on the parity-time symmetry optical structure

2022 ◽  
Vol 20 (2) ◽  
pp. 022201
Author(s):  
Lingjun Yi ◽  
Changhong Li
Keyword(s):  
Enhanced Absorption ◽  
Time Symmetry ◽  
Electrical Modulation ◽  
Optical Structure

scholarly journals Simulation Study of In-Phase and Out-Phase Enhanced Absorption of Graphene Based on Parity–Time Symmetry One-Dimensional Photonic Crystal Structure

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1513
Author(s):  
Lingjun Yi ◽  
Changhong Li
Keyword(s):  
Photonic Crystal ◽  
Electric Field ◽  
Optical Communication ◽  
Communication Systems ◽  
Pt Symmetry ◽  
Square Wave ◽  
Enhanced Absorption ◽  
Time Symmetry ◽  
Optical Communication Systems ◽  
Symmetry Structure

In the field of modern optical communication systems and photoelectric detection, new components with complex functions and excellent performance are urgently needed. In this paper, a graphene-based parity–time (PT) symmetry structure is proposed, which is achieved by preparing the graphene layer on the top of a PT-symmetry photonic crystal. The transfer matrix method was used to calculate the absorptance of graphene, and a unique amplified absorption effect was found. Meanwhile, the peak value and wavelength position of the absorption can be modulated via the applied electric field. The results show that by adjusting the negative square-wave electric field from −3.5 × 10−5 to −13.5 × 10−5 V/nm (or the positive square-wave electric field from 2 × 10−5 to 11 × 10−5 V/nm), the proposed structure can achieve in-phase (or out-phase) enhanced absorption for the communication wavelength 1550 nm, with the absorption of graphene from 17 to 28 dB (or 30 to 15 dB) corresponding to the square-wave modulation electric field change. The modulable absorption properties of graphene in the structure have potential in optoelectronic devices and optical communication systems.

scholarly journals Observation of anti-parity-time-symmetry, phase transitions and exceptional points in an optical fibre

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Arik Bergman ◽  
Robert Duggan ◽  
Kavita Sharma ◽  
Moshe Tur ◽  
Avi Zadok ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Brillouin Scattering ◽  
Optical Gain ◽  
Single Mode ◽  
Exceptional Point ◽  
Small Scale ◽  
Time Symmetry ◽  
Topological Features ◽  
Gain And Loss ◽  
Exotic Physics

AbstractThe exotic physics emerging in non-Hermitian systems with balanced distributions of gain and loss has recently drawn a great deal of attention. These systems exhibit phase transitions and exceptional point singularities in their spectra, at which eigen-values and eigen-modes coalesce and the overall dimensionality is reduced. So far, these principles have been implemented at the expense of precise fabrication and tuning requirements, involving tailored nano-structured devices with controlled optical gain and loss. In this work, anti-parity-time symmetric phase transitions and exceptional point singularities are demonstrated in a single strand of single-mode telecommunication fibre, using a setup consisting of off-the-shelf components. Two propagating signals are amplified and coupled through stimulated Brillouin scattering, enabling exquisite control over the interaction-governing non-Hermitian parameters. Singular response to small-scale variations and topological features arising around the exceptional point are experimentally demonstrated with large precision, enabling robustly enhanced response to changes in Brillouin frequency shift.

scholarly journals Ultra-Narrow Metallic Nano-Trenches Realized by Wet Etching and Critical Point Drying

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 783
Author(s):  
Jeeyoon Jeong ◽  
Hyosim Yang ◽  
Seondo Park ◽  
Yun Daniel Park ◽  
Dai-Sik Kim
Keyword(s):  
Critical Point ◽  
Terahertz Spectroscopy ◽  
High Surface ◽  
Wet Etching ◽  
Drying Process ◽  
Metal Structures ◽  
Critical Point Drying ◽  
Metal Insulator Metal ◽  
Gap Width ◽  
Optical Structure

A metallic nano-trench is a unique optical structure capable of ultrasensitive detection of molecules, active modulation as well as potential electrochemical applications. Recently, wet-etching the dielectrics of metal–insulator–metal structures has emerged as a reliable method of creating optically active metallic nano-trenches with a gap width of 10 nm or less, opening a new venue for studying the dynamics of nanoconfined molecules. Yet, the high surface tension of water in the process of drying leaves the nano-trenches vulnerable to collapsing, limiting the achievable width to no less than 5 nm. In this work, we overcome the technical limit and realize metallic nano-trenches with widths as small as 1.5 nm. The critical point drying technique significantly alleviates the stress applied to the gap in the drying process, keeping the ultra-narrow gap from collapsing. Terahertz spectroscopy of the trenches clearly reveals the signature of successful wet etching of the dielectrics without apparent damage to the gap. We expect that our work will enable various optical and electrochemical studies at a few-molecules-thick level.

scholarly journals How the amount of cracks and potholes grows with time: Symmetry-based explanation of empirical dependencies

2020 ◽  
Author(s):  
Edgar Daniel Rodriguez Velasquez ◽  
Olga Kosheleva ◽  
Vladik Kreinovich
Keyword(s):  
Time Symmetry

Electrochemical preparation of vertically aligned, hollow CdSe nanotubes and their p–n junction hybrids with electrodeposited Cu2O

Nanoscale ◽  
2014 ◽  
Vol 6 (15) ◽  
pp. 9148-9156 ◽  
Author(s):  
Joyashish Debgupta ◽  
Ramireddy Devarapalli ◽  
Shakeelur Rahman ◽  
Manjusha V. Shelke ◽  
Vijayamohanan K. Pillai
Keyword(s):  
Charge Carriers ◽  
Type Ii ◽  
Electrochemical Preparation ◽  
Enhanced Absorption ◽  
Absorption Of Light ◽  
Vertically Aligned ◽  
P Type

Heterojunction (type II) of self standing, vertically aligned CdSe NTs (n-type) with electrodeposited Cu2O (p-type) exhibits excellent photoresponse, resulting from enhanced absorption of light and faster transport of photogenerated charge carriers by CdSe NTs.

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