scholarly journals Observation of light induced dynamical band structure via multi-band high harmonic spectroscopy

2021 ◽  
Author(s):  
Ayelet Uzan-Narovlansky ◽  
Alvaro Jimenez-Galan ◽  
Gal Orenstein ◽  
Rui Silva ◽  
Talya Arusi-Parpar ◽  
...  
Keyword(s):  
Band Structure ◽  
Electric Field ◽  
Band Gap ◽  
Voltage Drop ◽  
High Harmonic ◽  
Probe Laser ◽  
All Optical ◽  
Oscillating Electric Field ◽  
Light Matter Interaction ◽  
Intense Light

Abstract Intense light-matter interactions have revolutionized our ability to probe and manipulate quantum systems at sub-femtosecond time scales, opening routes to all-optical control of electronic currents in solids at petahertz rates, the time-scale of a single optical cycle. Such control typically requires electric field amplitudes ~V/A, when the voltage drop across a lattice site becomes comparable to the characteristic band gap energies. In this regime, intense light-matter interaction induces significant modifications of electronic and optical properties and is certain to dramatically modify the band structure of the light-dressed crystal. Yet, identifying and characterizing such modifications remains an outstanding problem. As the oscillating electric field changes from V/A to zero within a quarter-cycle of the driving field, does the band-structure follow, and how can it be defined? Here we address this fundamental question, proposing all-optical spectroscopy of strongly driven crystals, and probe laser-induced closing of the band-gap between adjacent conduction bands. Our work reveals the link between extreme nonlinear light matter interactions in strongly driven crystals to the sub-cycle modifications in their effective band structure.

Engineering difference of band structure between mirror symmetrical adsorption and antisymmetrical adsorption of the identical group on a graphene sheet

2019 ◽  
Vol 85 (3) ◽  
pp. 30101
Author(s):  
Xinyue Zhang ◽  
Qingsong Huang
Keyword(s):  
Band Structure ◽  
Electric Field ◽  
Band Gap ◽  
Graphene Sheet ◽  
Functional Groups ◽  
Mirror Symmetry ◽  
Dominant Factor ◽  
Bonding State ◽  
Adsorption Sites ◽  
Continuous Tuning

Symmetry of adsorption site is the key to control the graphene band gap. When the adsorption sites change from mirror-symmetry adsorption (MSA) to mirror antisymmetric adsorption (MAA) position, the bandgap change (BC) exhibits two opposite tendencies. Therefore, a standard was developed to determine the type of band gap modification of graphene. When BC is negative, the bonding state between the adsorbent and graphene was the dominant factor. When BC is positive, the built-in electric field becomes dominated. Continuous tuning of the band gap can be achieved by adsorbing the appropriate functional groups. Our findings set the standard for determining the type of band gap modification and open the way for controllable adjustment of graphene band gap.

scholarly journals Meta-Deflectors Made of Dielectric Nanohole Arrays with Anti-Damage Potential

Photonics ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 107
Author(s):  
Haichao Yu ◽  
Feng Tang ◽  
Jingjun Wu ◽  
Zao Yi ◽  
Xin Ye ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Laser Cutting ◽  
High Complexity ◽  
Damage Potential ◽  
Optical Components ◽  
Nanohole Arrays ◽  
Intense Light ◽  
Polarization Of Light ◽  
Air Hole

In intense-light systems, the traditional discrete optical components lead to high complexity and high cost. Metasurfaces, which have received increasing attention due to the ability to locally manipulate the amplitude, phase, and polarization of light, are promising for addressing this issue. In the study, a metasurface-based reflective deflector is investigated which is composed of silicon nanohole arrays that confine the strongest electric field in the air zone. Subsequently, the in-air electric field does not interact with the silicon material directly, attenuating the optothermal effect that causes laser damage. The highest reflectance of nanoholes can be above 99% while the strongest electric fields are tuned into the air zone. One presentative deflector is designed based on these nanoholes with in-air-hole field confinement and anti-damage potential. The 1st order of the meta-deflector has the highest reflectance of 55.74%, and the reflectance sum of all the orders of the meta-deflector is 92.38%. The optothermal simulations show that the meta-deflector can theoretically handle a maximum laser density of 0.24 W/µm2. The study provides an approach to improving the anti-damage property of the reflective phase-control metasurfaces for intense-light systems, which can be exploited in many applications, such as laser scalpels, laser cutting devices, etc.

scholarly journals Band-Gap Solitons in Nonlinear Photonic Crystal Waveguides and Their Application for Functional All-Optical Logic Gating

Photonics ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 250
Author(s):  
Vakhtang Jandieri ◽  
Ramaz Khomeriki ◽  
Tornike Onoprishvili ◽  
Daniel Erni ◽  
Levan Chotorlishvili ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Band Gap ◽  
Crystalline Silicon ◽  
Logic Gates ◽  
Photonic Crystal Waveguides ◽  
Optical Logic ◽  
Logical Operation ◽  
Pulse Envelope ◽  
Gap Soliton ◽  
All Optical

This review paper summarizes our previous findings regarding propagation characteristics of band-gap temporal solitons in photonic crystal waveguides with Kerr-type nonlinearity and a realization of functional and easily scalable all-optical NOT, AND and NAND logic gates. The proposed structure consists of a planar air-hole type photonic crystal in crystalline silicon as the nonlinear background material. A main advantage of proposing the gap-soliton as a signal carrier is that, by operating in the true time-domain, the temporal soliton maintains a stable pulse envelope during each logical operation. Hence, multiple concatenated all-optical logic gates can be easily realized paving the way to multiple-input ultrafast full-optical digital signal processing. In the suggested setup, due to the gap-soliton features, there is no need to amplify the output signal after each operation which can be directly used as a new input signal for another logical operation. The efficiency of the proposed logic gates as well as their scalability is validated using our original rigorous theoretical formalism confirmed by full-wave computational electromagnetics.

Band-gap engineering of the h-BN/MoS2/h-BN sandwich heterostructure under an external electric field

2015 ◽  
Vol 48 (20) ◽  
pp. 205302 ◽  
Author(s):  
Zongyu Huang ◽  
Xiang Qi ◽  
Hong Yang ◽  
Chaoyu He ◽  
Xiaolin Wei ◽  
...  
Keyword(s):  
Electric Field ◽  
Band Gap ◽  
External Electric Field ◽  
Band Gap Engineering

Parametric excitation in an inhomogeneous plasma

1971 ◽  
Vol 5 (1) ◽  
pp. 107-113 ◽  
Author(s):  
C. S. Chen
Keyword(s):  
Electric Field ◽  
Parametric Excitation ◽  
Growth Rates ◽  
Inhomogeneous Plasma ◽  
Electron Plasma ◽  
Transverse Waves ◽  
Circularly Polarized ◽  
Polarized Waves ◽  
Oscillating Electric Field ◽  
Unmagnetized Plasma

An infinite, inhomogeneous electron plasma driven by a spatially uniform oscillating electric field is investigated. The multi-time perturbation method is used to analyze possible parametric excitations of transverse waves and to evaluate their growth rates. It is shown that there exist subharmonic excitations of: (1) a pair of transverse waves in an unmagnetized plasma and (2) a pair of one right and one left circularly polarized wave in a magnetoplasma. Additionally, parametric excitation of two right or two left circularly polarized waves with different frequencies can exist in a magnetoplasma. The subharmonic excitations are impossible whenever the density gradient and the applied electric field are perpendicular. However, parametric excitation is possible with all configurations.

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