Phys.org March 31, 2023 Applying strong DC electric fields on the apex of a sharp metallic tip causes electrons to be emitted radially from the apex to vacuum magnifying the nanoscopic information on the apex, which serves as a field emission microscope (FEM). When depositing molecules on such a tip, peculiar electron emission patterns such as clover leaves appear. However, the source of these emission patterns has not yet been identified owing to the limited experimental information about molecular configurations on a tip. An international team of researchers (Japan, Germany, France) used fullerene molecules and characterized the molecule-covered tip by […]
Category Archives: Light
Research team develops multifunctional vortex beam for UV-visible spectra
Phys.org March 16, 2023 Metasurfaces have shown remarkable potential to manipulate many of light’s intrinsic properties, such as phase, amplitude, and polarization. An international team of researchers (Saudi Arabia, Macedonia, USA – New York University) has demonstrated a broadband multifunctional metasurface platform with the unprecedented ability to independently control the phase profile for two orthogonal polarization states of incident light over dual-wavelength spectra (ultraviolet to visible). They designed and fabricated multiple single-layered metasurfaces composed of bandgap-engineered silicon nitride nanoantennas and optically characterized to demonstrated broadband multifunctional light manipulation ability, including structured beam generation and meta-interferometer implementation. According to the researchers […]
Breakthrough discovery in materials science challenges current understanding of photoemission
Phys.org March 14, 2023 Currently existing photocathodes are based on conventional metals and semiconductors that were discovered six decades ago with sound theoretical underpinnings. An international team of researchers (China, Japan, USA- Northeastern University) has observed unusual photoemission properties of a reconstructed surface of SrTiO3(100) single crystals. Unlike other positive-electron-affinity (PEA) photocathodes, their PEA SrTiO3 surface produced discrete secondary photoemission spectra at room temperature, characteristic of the efficient negative-electron-affinity photocathode materials. Using several photon energies they were able to produce a very intense coherent secondary photoemission. According to the researchers the observed emergence of coherence in secondary photoemission points to […]
Scientists can now map lightning in 3D
Phys.org February 15, 2023 A team of researchers in the US (Los Alamos National Laboratory, New Mexico Institute of Mining and Technology) developed and deployed a new 3-dimensional broadband radio frequency interferometric mapping and polarization system (BIMAP-3D) which provides an unprecedented capability in high-resolution, time-evolving 3D lightning source mapping and 3D source polarization detection for detailed study of lightning discharge physics. In this article they described the BIMAP-3D system design, a generalized and analytical 2D interferometry technique for noncoplanar antenna array, a two-stage 3D mapping technique based on geometric triangulation and baseline-based differential time of arrival, and a technique to […]
Distortion-free structured light
Phys.org February 7, 2023 Both real-world and experimentally simulated turbulence conditions have revealed that free-space structured light modes are perturbed by turbulence resulting in both amplitude and phase distortions, and consequently, much attention has focused on whether one mode type is more robust than another, but with inconclusive and contradictory results. Researchers in South Africa have shown complex forms of structured light that are invariant under propagation through the atmosphere: the true eigenmodes of atmospheric turbulence. They provided a theoretical procedure for obtaining these eigenmodes and confirmed their invariance both numerically and experimentally. According to the researchers although they have […]
An illuminated water droplet creates an ‘optical atom’
Phys.org January 31, 2023 When light scatters off a sphere, it produces a rich Mie spectrum full of overlapping resonances. Single resonances can be explained with a quantum analogy and result in Fano profiles. However, the full spectrum is so complex that recognizable patterns have not been found, and is only understood by comparing to numerical simulations. An international team of researchers (Sweden, Mexico) has shown the directional Mie spectrum of evaporating water droplets arranged in consecutive Fano Combs. They explained it by expanding the quantum analogy. This turns the droplet into an “optical atom” with angular momentum, tunneling, and […]
Researchers control individual light quanta at very high speed
Phys.org November 21, 2022 An international team of researchers (Spain, Germany) fabricated a dynamically reconfigurable integrated photonic circuit comprising integrated quantum dots (QDs), a Mach-Zehnder interferometer (MZI) and surface acoustic wave (SAW) transducers directly fabricated on a monolithic semiconductor platform to demonstrate on-chip single photon generation by the QD and its sub-nanosecond dynamic on-chip control. Two independently applied SAWs piezo-optomechanically rotated the single photon in the MZI. In the MZI, SAWs imprinted a time-dependent optical phase and modulated the qubit rotation to the output superposition state. This enabled dynamic single photon routing with frequencies exceeding one gigahertz. The combination of […]
Breaking an optical rule: Engineers find a way to manipulate light at the nanoscale
Phys.org September 12, 2022 According to Moss rule the absorption edge and the sub-bandgap refractive index of a semiconductor exhibit a rigid trade-off setting an upper limit on the refractive index of a dielectric for a given operating wavelength. According to a team of researchers in the US (Rice University, Johns Hopkins University) there are many dielectric materials that surpass the Moss rule, referred to as super-Mossian dielectrics. They discussed the general features of super-Mossian dielectrics and their physical origin to facilitate the search for high index dielectrics. They developed iron pyrite with index nearly 40% higher than the Moss […]
A simple way of sculpting matter into complex shapes
Science Daily August 12, 2022 Researchers in the UK modeled propagation of far-red-detuned optical vortex beams through a Bose-Einstein condensate using nonlinear Schrödinger and Gross-Pitaevskii equations. They showed the formation of coupled light-atomic solitons that rotate azimuthally before moving off tangentially, carrying angular momentum. The number, and velocity, of solitons, depends on the orbital angular momentum of the optical field. Using a Bessel-Gauss beam increases radial confinement so that solitons can rotate with fixed azimuthal velocity. According to the researchers the model provides a highly controllable method of channeling a BEC and atomic transport…read more. TECHNICAL ARTICLE
The handedness of light holds the key to better optical control
Phys.org July 18, 2022 Current optical modulators used to manipulate the properties of a beam of light mainly use electrical or acoustic effects. These technologies can control the properties of light at nanosecond speeds. Researchers in Finland have developed an all-optical modulator technique which uses a coherent optical process. It can work at femtosecond speeds. They experimentally validated the concept in monolayer materials (MoS2) with modulation depth approaching ~100%, ultra-fast modulation speed (<~130 fs), and wavelength-independence features. The power and polarization of the incident optical beams can be used to tune the output chirality and modulation performance. According to the researchers […]