Strong electric field enhancements in asymmetric metallic nanostructures and high-order harmonic generation

Ebadian, H.; Mohebbi, Masoud

doi:10.1364/ao.55.008035

Cited by 9 publications

(2 citation statements)

References 27 publications

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“…Harmonic phenomena have a well-established presence in fields of sonics and electric circuits. 39–41 Similarly, such harmonic phenomena can be observed in EEG or local field potential signals, potentially linked to specific brain functional states. 42,43 For instance, during NREM sleep, sleep spindles exhibit harmonic phenomena, with parameters changing in accordance with sleep stages, reflecting functional alterations in the thalamocortical reverberant network.…”

Section: Discussionmentioning

confidence: 99%

Harmonic patterns embedding ictal EEG signals in focal epilepsy: new insight into the epileptogenic zone

Hu,

Ye,

et al. 2023

Preprint

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The ictal EEG biomarkers of the epileptogenic zone (EZ) need to be better defined. The power and structure of ictal fast activity are important in EZ localization, but EEG onset patterns are heterogeneous and initial fast activity is absent in many patients. Here we defined a unique spectral structure of “harmonic pattern” (H pattern) on stereo-EEG (SEEG), characterized by multiple equidistant, high-density bands with varying frequency on time frequency map. H pattern was commonly observed among 57 (81.4%) out of 70 patients with focal onset pattern on SEEG. It was presented in seizures with various ictal onset patterns with or without fast activity, and during early or late stage of seizures. H pattern usually expressed at very close time point across the seizure onset zone (SOZ), primary propagation zone and sometimes other areas, with the same fundamental difference, reflecting an inter-regional synchronization within the ictal network during this time. Notably, SOZ showed the highest proportion of channels expressing H-pattern, and also highest band number of H-pattern. At patient level, the dominant H pattern was defined as those with high rank in band numbers (the third quartile, Q3). Resection of the region expressing dominant H pattern, but not SOZ, independently predicted seizure freedom after surgery, suggesting it is an ictal marker of EZ. How H pattern was produced was then investigated. It only embedded into two types of EEG segments: fast activity with a frequency >25Hz (FA-H pattern) at early seizure propagation (mean 13.3 sec after onset), and irregular polyspikes (> 5 Hz, PS-H pattern) during late propagation (mean 23.3 sec after onset). Nonlinear analysis was used to unravel the mechanism underlying H pattern generation. Our data showed it was produced by specific nonlinear phenomena rather than intermodulation of frequencies or purely methodological artefact. The nonlinearity was stronger for dominant compared to non-dominant H pattern. According to the spectral parameters, we postulate that FA-H pattern may be supported by a predominant and synchronized firing of GABAergic neurons, while excitatory neuron firing is more important for PS-H pattern. As a distinctive and common ictal spectral feature, H pattern conveys unique information of ictal neural dynamics and provides new insights into the EZ. Our study also provides evidence that there is an elongated time-window to measure EZ using quantitative EEG.

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Section: Discussionmentioning

confidence: 99%

Harmonic patterns embedding ictal EEG signals in focal epilepsy: new insight into the epileptogenic zone

Hu,

Ye,

et al. 2023

Preprint

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“…The related interaction Hamiltonian term is V I (x, t) = xE (x, t), and E (x, t) = E(t)g(x), and g(x) represents the functional form of the inhomogeneous electric field, which can be obtained by fitting the actual electric field [18].…”

Section: Hhg Spectrummentioning

confidence: 99%

Plasmonic nanostructure assisted HHG in NIR spectrum and thermal analysis

Ebadian

Mohebbi

2018

J. Phys. D: Appl. Phys.

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We study plasmonic nanoparticle assisted high-order harmonic generation (HHG), illuminated by near infrared (NIR) laser sources, and the effect of the geometry of some different dimers on HHG cutoff frequency is evaluated. Dimers are installed on different dielectric substrates and the electric field enhancement factors are simulated. We demonstrate that NIR femtofiber sources are good options for the HHG process. Such sources can induce significant inhomogeneous electric fields in the nanogaps; and consequently, high harmonic cutoff orders more than 250 will be obtained. Moreover, by time dependent thermal analysis of Au nanoparticles exposed to NIR ultrafast high power lasers, we could determine the temperature distribution in the nanoparticle and substrate.

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Laser interaction with a MIM nanostructure including bowtie aperture and cylindrical holes for plasmonic field enhancement based on strong coupling of LSPR and SPPs

Atefeh,

Masoud

2024

J Comput Electron

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Strong electric field enhancements in asymmetric metallic nanostructures and high-order harmonic generation

Cited by 9 publications

References 27 publications

Harmonic patterns embedding ictal EEG signals in focal epilepsy: new insight into the epileptogenic zone

Harmonic patterns embedding ictal EEG signals in focal epilepsy: new insight into the epileptogenic zone

Plasmonic nanostructure assisted HHG in NIR spectrum and thermal analysis

Laser interaction with a MIM nanostructure including bowtie aperture and cylindrical holes for plasmonic field enhancement based on strong coupling of LSPR and SPPs

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