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Register a new userExtraordinary nonlinear optics in ordinary semiconductors
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We numerically demonstrate inhibition of absorption, optical transparency, and anomalous momentum states of phase locked harmonic pulses in semiconductors, at UV and extreme UV frequencies, in spectral regions where the dielectric constant of typical semiconductors is negative. We show that a generated harmonic signal can propagate through a bulk metallic medium without being absorbed as a result of a phase locking mechanism between the pump and its harmonics. These findings may open new regimes in nonlinear optics and are particularly relevant to the emerging fields of nonlinear negative index meta-materials and nano-plasmonics, especially in the ultrafast pulse regime.
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Nonlinear optical methods are becoming ubiquitous in many areas of modern photonics. They are, however, often limited to a certain range of input parameters, such as pulse energy and average power, since restrictions arise from, for example, parasitic nonlinear effects, damage problems and geometrical considerations. Here, we show that many nonlinear optics phenomena in gaseous media are scale-invariant if spatial coordinates, gas density and laser pulse energy are scaled appropriately. We develop a general scaling model for (3+1)-dimensional wave equations, demonstrating the invariant scaling of nonlinear pulse propagation in gases. Our model is numerically applied to high-order harmonic generation and filamentation as well as experimentally verified using the example of pulse post-compression via filamentation. Our results provide a simple recipe for up-or downscaling of nonlinear processes in gases with numerous applications in many areas of science.
Particles or waves scattered from a rotating black hole can be amplified through the process of Penrose superradiance, though this cannot currently be observed in an astrophysical setting. However, analogue gravity studies can create generic rotating geometries exhibiting an ergoregion, and this led to the first observation of Penrose superradiance as the over-reflection of water waves from a rotating fluid vortex. Here we theoretically demonstrate that Penrose superradiance arises naturally in the field of nonlinear optics. In particular, we elucidate the mechanism by which a signal beam can experience gain or amplification as it glances off a strong vortex pump beam in a nonlinear defocusing medium. This involves the trapping of negative norm modes in the core of the pump vortex, as predicted by Penrose, which in turn provides a gain mechanism for the signal beam. Our results elucidate a new regime of nonlinear optics involving the notion of an ergoregion, and provide further insight into the processes involved in Penrose superradiance.
I present an overview of pulse propagation methods used in nonlinear optics, covering both full-field and envelope-and-carrier methods. Both wideband and narrowband cases are discussed. Three basic forms are considered -- those based on (a) Maxwells equations, (b) directional fields, and (c) the second order wave equation. While Maxwells equations simulators are the most general, directional field methods can give significant computational and conceptual advantages. Factorizations of the second order wave equation complete the set by being the simplest to understand. One important conclusion is that that envelope methods based on forward-only directional field propagation has made the traditional envelope methods (such as the SVEA, and extensions) based on the second order wave equation utterly redundant.
Symmetries and their associated selection rules are extremely useful in all fields of science. In particular, for system that include electromagnetic (EM) fields interacting with matter, it has been shown that both of symmetries of matter and EM fields time-dependent polarization play a crucial role in determining the properties of linear and nonlinear responses. The relationship between the systems symmetry and the properties of its excitations facilitate precise control over light emission and enable ultrafast symmetry-breaking spectroscopy of variety of properties. Here. we formulate the first general theory that describes the macroscopic dynamical symmetries (including quasicrystal-like symmetries) of an EM vector field, revealing many new symmetries and selection rules in light-matter interactions. We demonstrate an example of multi-scale selection rules experimentally in the framework of high harmonic generation (HHG). This work waves the way for novel spectroscopic techniques in multi-scale system as well as for imprinting complex structures in EUV-X-ray beams, attosecond pulses, or the interacting medium itself.
We propose that ordinary semiconductors with large spin-orbit coupling (SOC), such as GaAs, can host stable, robust, and {it tunable} topological states in the presence of quantum confinement and superimposed potentials with hexagonal symmetry. We show that the electronic gaps which support chiral spin edge states can be as large as the electronic bandwidth in the heterostructure miniband. The existing lithographic technology can produce a topological insulator (TI) operating at temperature $10- 100K$. Improvement of lithographic techniques will open way to tunable room temperature TI.
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