scholarly journals Controlling Refraction Using Sub-Wavelength Resonators

2018 ◽  
Vol 8 (10) ◽  
pp. 1942
Author(s):  
Yue Chen ◽  
Robert Lipton
Keyword(s):  
Frequency Dependence ◽  
Free Space ◽  
Near Infrared ◽  
Center Frequency ◽  
Negative Index ◽  
Index Properties ◽  
Frequency Bands ◽  
Transmitted Signal ◽  
Sub Wavelength

We construct metamaterials from sub-wavelength nonmagnetic resonators and consider the refraction of incoming signals traveling from free space into the metamaterial. We show that the direction of the transmitted signal is a function of its center frequency and bandwidth. The directionality of the transmitted signal and its frequency dependence is shown to be explicitly controlled by sub-wavelength resonances that can be calculated from the geometry of the sub-wavelength scatters. We outline how to construct a medium with both positive and negative index properties across different frequency bands in the near infrared and optical regime.

scholarly journals Interferometric characterization of a sub-wavelength near-infrared negative index metamaterial

2010 ◽  
Vol 18 (17) ◽  
pp. 17788 ◽  
Author(s):  
Xuhuai Zhang ◽  
Marcelo Davanço ◽  
Kara Maller ◽  
Thomas W. Jarvis ◽  
Chihhui Wu ◽  
...  
Keyword(s):  
Near Infrared ◽  
Negative Index ◽  
Sub Wavelength

scholarly journals Observing and controlling a Tamm plasmon at the interface with a metasurface

Nanophotonics ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 897-903 ◽  
Author(s):  
Oleksandr Buchnev ◽  
Alexandr Belosludtsev ◽  
Victor Reshetnyak ◽  
Dean R. Evans ◽  
Vassili A. Fedotov
Keyword(s):  
Liquid Crystal ◽  
Metal Film ◽  
Near Infrared ◽  
Thin Metal Film ◽  
Outer Side ◽  
Spectral Position ◽  
External Perturbations ◽  
Dielectric Mirror ◽  
Wavelength Scale ◽  
Sub Wavelength

AbstractWe demonstrate experimentally that Tamm plasmons in the near infrared can be supported by a dielectric mirror interfaced with a metasurface, a discontinuous thin metal film periodically patterned on the sub-wavelength scale. More crucially, not only do Tamm plasmons survive the nanopatterning of the metal film but they also become sensitive to external perturbations as a result. In particular, by depositing a nematic liquid crystal on the outer side of the metasurface, we were able to red shift the spectral position of Tamm plasmon by 35 nm, while electrical switching of the liquid crystal enabled us to tune the wavelength of this notoriously inert excitation within a 10-nm range.

scholarly journals Multimodal Autoencoder Predicts fNIRS Resting State From EEG Signals

2021 ◽  
Author(s):  
Parikshat Sirpal ◽  
Rafat Damseh ◽  
Ke Peng ◽  
Dang Khoa Nguyen ◽  
Frédéric Lesage
Keyword(s):  
Near Infrared ◽  
Short Term Memory ◽  
A Priori ◽  
Functional Near Infrared Spectroscopy ◽  
Neural Data ◽  
Frequency Bands ◽  
Epileptic Patients ◽  
Brain Hemodynamics ◽  
Long Short Term Memory ◽  
Trained Neural Network

AbstractIn this work, we introduce a deep learning architecture for evaluation on multimodal electroencephalographic (EEG) and functional near-infrared spectroscopy (fNIRS) recordings from 40 epileptic patients. Long short-term memory units and convolutional neural networks are integrated within a multimodal sequence-to-sequence autoencoder. The trained neural network predicts fNIRS signals from EEG, sans a priori, by hierarchically extracting deep features from EEG full spectra and specific EEG frequency bands. Results show that higher frequency EEG ranges are predictive of fNIRS signals with the gamma band inputs dominating fNIRS prediction as compared to other frequency envelopes. Seed based functional connectivity validates similar patterns between experimental fNIRS and our model’s fNIRS reconstructions. This is the first study that shows it is possible to predict brain hemodynamics (fNIRS) from encoded neural data (EEG) in the resting human epileptic brain based on power spectrum amplitude modulation of frequency oscillations in the context of specific hypotheses about how EEG frequency bands decode fNIRS signals.

Energy efficiency of near infrared cobalt luminscence in ZnSe:Co determined by a photoacoustic method

2012 ◽  
Vol 20 (1) ◽  
Author(s):  
Ł. Chrobak ◽  
M. Maliński ◽  
K. Strzałkowski ◽  
J. Zakrzewski
Keyword(s):  
Energy Efficiency ◽  
Frequency Dependence ◽  
Near Infrared ◽  
Transmission Spectra ◽  
Photoacoustic Method ◽  
Infrared Luminescence ◽  
Amplitude Characteristics

AbstractThe paper presents results of computations of the energy efficiency of the cobalt luminescence in ZnSe:Co determined by the photoacoustic method. The transmission spectra, photoacoustic experimental and theoretical spectra, and the frequency dependence on the photoacoustic amplitude characteristics are presented. From them, the energy efficiency of Co2+ the near infrared luminescence (3200 nm) was computed in the frame of new proposed photoacoustic model of computations of the luminescence energy efficiency.

Free space microwave focusing by a negative-index gradient lens

2006 ◽  
Author(s):  
T. Driscoll ◽  
D. N. Basov ◽  
P. M. Rye ◽  
S. Nemat-Nasser ◽  
D. Schurig ◽  
...  
Keyword(s):  
Free Space ◽  
Negative Index ◽  
Index Gradient

Magnetic modulation of Fano resonances in optically thin terahertz superlattice metasurfaces

2021 ◽  
Author(s):  
Subhajit Karmakar ◽  
Ravi Varshney ◽  
Dibakar Roy Chowdhury
Keyword(s):  
Magnetic Field ◽  
Free Space ◽  
Skin Depth ◽  
Electromagnetic Energy ◽  
Magnetic Control ◽  
Fano Resonances ◽  
Electromagnetic Responses ◽  
On Chip ◽  
Magneto Resistance ◽  
Sub Wavelength

Abstract Optically thin metasurfaces operating at sub-skin depth thicknesses are intriguing because of its associated low plasmonic losses (compared to optically thick, beyond skin-depth metasurfaces). However, their applicability has been restricted largely because of reduced free space coupling with incident radiations resulting in limited electromagnetic responses. To overcome such limitations, we propose enhancement of effective responses (resonances) in sub-skin depth metasurfaces through incorporation of magneto-transport (Giant Magneto Resistance, GMR) concept. Here, we experimentally demonstrate dynamic magnetic modulation of structurally asymmetric metasurfaces (consisting of superlattice arrangement of thin (~ 10 nm each) magnetic (Ni)/ nonmagnetic (Al) layers) operating at terahertz (THz) domain. With increasing magnetic field (applied from 0 to 30 mT approximately, implies increasing superlattice conductivity), we observe stronger confinement of electromagnetic energy at the resonances (both in dipole and Fano modes). Therefore, this study introduces unique magnetically reconfigurable ability in Fano resonant THz metamaterials, which directly improves its performances operating in the sub-skin depth regime. Our study can be explained by spin-dependent terahertz magneto-transport phenomena in metals and can stimulate the paradigm for on-chip spin-based photonic technology enabling dynamic magnetic control over compact, sub-wavelength, sub-skin depth metadevices.

Field experiment and analysis for free-space laser transmission characteristic in turbulent path based on MWIR and NIR

2020 ◽  
Vol 34 (14) ◽  
pp. 2050148
Author(s):  
Wei Wang ◽  
Zhaofeng Bai ◽  
Xiaoping Xie ◽  
Haiping Mei ◽  
Wei Zhao
Keyword(s):  
Free Space ◽  
Background Noise ◽  
Communication Systems ◽  
Near Infrared ◽  
Transmission Characteristic ◽  
Free Space Optical ◽  
Atmospheric Attenuation ◽  
Atmospheric Transmission ◽  
Experimental Scheme ◽  
Quality Signals

It is hard to achieve low bit error rate (BER) and high-quality signals in free-space optical (FSO) communication systems due to atmospheric link interference. For the sake of seeking solutions, we proposed an experimental scheme of free-space laser communication based on middle-wave infrared (MWIR) and near infrared (NIR) for obtaining atmospheric transmission characteristic in 1 km turbulence path. Compared with NIR waveband, MWIR-based scheme is more suitable for atmospheric FSO communication since it owns higher anti-interference ability for atmospheric attenuation, turbulence and skylight background noise. The experimental results may offer a significant reference for FSO communication in atmosphere link.

scholarly journals Electrodeposited Negative Index Metamaterials with Visible and Near Infrared Response

2020 ◽  
Vol 8 (19) ◽  
pp. 2000865
Author(s):  
Mayte Gómez‐Castaño ◽  
Juan Luis Garcia‐Pomar ◽  
Luis Alberto Pérez ◽  
Sharvina Shanmugathasan ◽  
Serge Ravaine ◽  
...  
Keyword(s):  
Near Infrared ◽  
Negative Index
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