Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userControl of high-harmonic generation by tuning the electronic structure and carrier injection
110
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
High-harmonic generation (HHG), which is generation of multiple optical harmonic light, is an unconventional nonlinear optical phenomenon beyond perturbation regime. HHG, which was initially observed in gaseous media, has recently been demonstrated in solid state materials. How to control the extreme nonlinear optical phenomena is a challenging subject. Compared to atomic gases, solid state materials have advantages in controlling electronic structures and carrier injection. Here, we demonstrate control of HHG by tuning electronic structure and carrier injection using single-walled carbon nanotubes (SWCNTs). We reveal systematic changes in the high-harmonic spectra of SWCNTs with a series of electronic structures from a metal to a semiconductor. We demonstrate enhancement or reduction of harmonic generation by more than one order of magnitude by tuning electron and hole injection into the semiconductor SWCNTs through electrolyte gating. These results open a way to control HHG within the concept of field effect transistor devices.
rate research
Read More
Films of the topological insulator Bi2Se3 are grown by molecular beam epitaxy with in-situ reflection high-energy electron diffraction. The films are shown to be high-quality by X-ray reflectivity and diffraction and atomic-force microscopy. Quantum interference control of photocurrents is observed by excitation with harmonically related pulses and detected by terahertz radiation. The injection current obeys the expected excitation irradiance dependence, showing linear dependence on the fundamental pulse irradiance and square-root irradiance dependence of the frequency-doubled optical pulses. The injection current also follows a sinusoidal relative-phase dependence between the two excitation pulses. These results confirm the third-order nonlinear optical origins of the coherently controlled injection current. Experiments are compared to a tight-binding band structure to illustrate the possible optical transitions that occur in creating the injection current.
We theoretically investigate the piezo-optic effect of high-harmonic generation (HHG) in shear-strained semiconductors. By focusing on a typical semiconductor, GaAs, we show that there is optical activity, meaning different responses to right-handed and left-handed elliptically polarized electric fields. We also show that this optical activity is more pronounced for higher harmonics whose perturbative order exceeds the band-gap energy. These findings point to a useful pathway for strain engineering of nonlinear optics to control the reciprocity of HHG.
Light with light control of surface plasmon polaritons is theoretically demonstrated. A barely simple and compact source of these waves consists in a finite number of slits (evenly spaced) perforating a metal film. The system scatters electromagnetic fields in one side of the metal film when it is illuminated from the opposite side by a polarized light source. High intensity light sources moreover efficiently generate light at second harmonic and higher frequencies in the metal led by optical nonlinearities. It is shown how the mixing of fields scattered by the slits from a weak beam at $lambda$ wavelength, with the second harmonic fields generated by a high intensity $2 lambda$ beam, creates a destructive interference of surface plasmons in one of the two possible directions of emission from the slits, while these are enhanced along the opposite direction. The unidirectional launching of surface plasmons is due to the different properties of symmetry at $lambda$ whether they are linearly or nonlinearly generated. It is envisaged a nanodevice which might allow sending digital information codified in the surface plasmon field or be used to build ultra-narrow bandwidth surface plasmon frequency combs.
Efficient frequency conversion techniques are crucial to the development of plasmonic metasurfaces for information processing and signal modulation. In principle, nanoscale electric-field confinement in nonlinear materials enables higher harmonic conversion efficiencies per unit volume than those attainable in bulk materials. Here we demonstrate efficient second-harmonic generation (SHG) in a serrated nanogap plasmonic geometry that generates steep electric field gradients on a dielectric metasurface. An ultrafast pump is used to control plasmon-induced electric fields in a thin-film material with inversion symmetry that, without plasmonic enhancement, does not exhibit an an even-order nonlinear optical response. The temporal evolution of the plasmonic near-field is characterized with ~100as resolution using a novel nonlinear interferometric technique. The ability to manipulate nonlinear signals in a metamaterial geometry as demonstrated here is indispensable both to understanding the ultrafast nonlinear response of nanoscale materials, and to producing active, optically reconfigurable plasmonic devices
The process of tunneling injection is known to improve the dynamical characteristics of quantum well and quantum dot lasers; in the latter, it also improves the temperature performance. The advantage of the tunneling injection process stems from the fact that it avoids hot carrier injection, which is a key performance-limiting factor in all semiconductor lasers. The tunneling injection process is not fully understood microscopically and therefore it is difficult to optimize those laser structures. We present here a numerical study of the broad band carrier dynamics in a tunneling injection quantum dot gain medium in the form of an optical amplifier operating at 1.55 um. Charge carrier tunneling occurs in a hybrid state that joins the quantum dot first excited state and the confined quantum well - injection well states. The hybrid state, which is placed energetically roughly one LO phonon above the ground state and has a spectral extent of about 5 meV , dominates the carrier injection to the ground state. We calculate the dynamical response of the inversion across the entire gain spectrum following a short pulse perturbation at various wavelengths and for two bias currents. At a high bias of 200 mA, the entire spectrum exhibits gain; at 30 mA, the system exhibits a mixed gain - absorption spectrum. The carrier dynamics in the injection well is calculated simultaneously. We discuss the role of the pulse excitation wavelengths relative to the gain spectrum peak and demonstrate that the injection well responds to all perturbation wavelengths, even those which are far from the region where the tunneling injection process dominates.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
