Scientists push the boundaries of manipulating light at the submicroscopic level

Phys.org  March 2, 2023 How tightly the light is confined determines the limits for the observability of nanoparticles, as well as the intensity and the precision of light-based devices. An international team of researchers (UK, Germany) has developed a general theory describing multi-mode light–matter coupling in systems of reduced dimensionality. The researchers explored their phenomenology, validating their theory’s predictions against numerical electromagnetic simulations. They characterized the spectral features linked with the multi-mode nature of the polaritons and showed how the interference between different photonic resonances can modify the real-space shape of the electromagnetic field associated with each polariton mode. According […]

Nanoparticles make it easier to turn light into solvated electrons

Nanowerk  January 17, 2023 Solvated electrons are powerful reducing agents capable of driving some of the most energetically expensive reduction reactions. It has been proposed that solvated electrons, which are powerful reducing agents, could be produced by photoexcitation of roughened metal electrodes, but no study has demonstrated a clear mechanism for their generation. A team of researchers in the US (Rice University, Stanford University, UT Austin) has shown that plasmons create solvated electrons in water. They showed that the yield of solvated electrons in water was increased more than 10 times for nanoparticle-decorated electrodes compared to smooth silver electrodes. Based […]

Electrons on the run: On chirality, tunneling and light fields

Phys.org  December 23, 2022 Tunnel ionization is of paramount importance in strong-field physics and attoscience. However, the tunneling dynamics and properties of the outgoing electronic wave packets often remain hidden beneath the influence of the subsequent scattering of the released electron onto the ionic potential. An international team of researchers (France, Israel) has characterized the influence of sub-barrier dynamics on the amplitude and phase of the wave packets emerging from the tunnel using chiral molecules, whose photoionization by circularly polarized light produces forward-backward asymmetric electron distributions with respect to the light propagation direction. The asymmetric patterns provided a background-free signature […]

Researchers unlock light-matter interactions on sub-nanometer scales, leading to ‘picophotonics’

Phys.org  November 16, 2022 The concept of photonic frequency-momentum (ω-q) dispersion has been extensively studied in artificial dielectric structures such as photonic crystals and metamaterials, but not in in natural materials at the atomistic level. Researchers at Purdue University have developed a Maxwell Hamiltonian theory of matter combined with the quantum theory of atomistic polarization to obtain the electrodynamic dispersion of natural materials interacting with the photon field. They applied this theory to silicon and discovered the existence of anomalous atomistic waves. These waves occur in the spectral region where propagating waves are conventionally forbidden in a macroscopic theory. According […]

Light-driven molecular swing

Science Daily  October 18, 2022 An international team of researchers (Germany, USA – UC Irvine) used electric-field-resolved spectroscopy and quantum-chemical modelling to precisely measure and describe the complete coherent energy transfer between octave-spanning mid-infrared waveforms and vibrating molecules in aqueous solution. The sub-optical-cycle temporal resolution of their technique revealed alternating absorption and (stimulated) emission on a few-femtosecond time scale. This behaviour can only be captured when effects beyond the rotating wave approximation are considered. At a femtosecond-to-picosecond timescale, optical-phase-dependent coherent transients, and the dephasing of the vibrations of resonantly excited methylsulfonylmethane (DMSO2) were observed. Ab initio modelling using density functional […]

A molecule of light and matter

Science Daily  August 1, 2022 An international team of researchers (Austria, Germany) has observed a mechanical deformation of a cloud of ultracold 87Rb atoms due to the collective interplay of the atoms and a homogenous light field. This collective light scattering resulted in a self-confining potential with interesting features: It exhibited nonlocal properties, attractive for both red- and blue-detuned light fields and induced a remarkably strong force that depends on the gradient of the atomic density. In the article they discuss their experimental observations framework of a theoretical model based on a local-field approach for the light scattered by the […]

Researchers measure the binding state of light and matter for the first time

Phys.org  August 1, 2022 Light-matter interaction is well understood on the single-atom level and routinely used to manipulate atomic gases. However, in denser ensembles, collective effects emerge that are caused by light-induced dipole-dipole interactions and multiple photon scattering. An international team of researchers (Austria, Germany) found a mechanical deformation of a cloud of ultracold 87Rb atoms due to the collective interplay of the atoms and a homogenous light field. The collective light scattering results in a self-confining potential which exhibits nonlocal properties, attractive for both red- and blue-detuned light fields and induces a remarkably strong force that depends on the […]

Atomically-smooth gold crystals help to compress light for nanophotonic applications

Phys.org  July 13, 2022 An international team of researchers (South Korea, Denmark, Switzerland, Japan, USA – University of Minnesota) used a highly sensitive scanning near-field optical microscope (SNOM) to directly measure the optical fields of the hyperbolic image phonon-polaritons (HIP) propagating in a 63 nm-thick slab of hexagonal boron nitride (h-BN) on a monocrystalline gold substrate, showing the mid-infrared light waves in dielectric crystal compressed by a hundred times. They showed that the phonon-polaritons in van der Waals crystals can be significantly more compressed without sacrificing their lifetime. Practically zero surface scattering and extremely small ohmic loss in gold at […]

Nanoparticles control flow of light like road signs direct traffic

Science Daily  June 20, 2022 An class of metasurface functionalities is associated with asymmetry in both the generation and transmission of light with respect to reversals of the positions of emitters and receivers. The nonlinear light–matter interaction in metasurfaces offers a promising pathway towards miniaturization of the asymmetric control of light. An international team of researchers (Germany, Australia, Singapore) has demonstrated asymmetric parametric generation of light in nonlinear metasurfaces by assembling dissimilar nonlinear dielectric resonators into translucent metasurfaces that produce images in the visible spectral range on being illuminated by infrared radiation. By design, the metasurfaces produce different and completely […]

It’s a trap! Laser light ensnared by invisible bonds

Science Daily  June 1, 2022 Anderson localization predicts that transport in one-dimensional uncorrelated disordered systems comes to a complete halt, experiencing no transport whatsoever. However, a disordered physical system is always correlated because it must have a finite spectrum. Localization is dominant only for wave packets whose spectral extent resides within the region of the wave number span of the disorder. An international team of researchers (Israel, Germany, Spain) has experimentally shown that Anderson localization can occur and even be dominant for wave packets residing entirely outside the spectral extent of the disorder. The team studied the evolution of wave […]