Nanowerk October 16, 2023 An international team of researchers (Japan, Spain) demonstrated electromagnetic waves following a gravitational field using a photonic crystal. They introduced spatially distorted photonic crystals (DPCs) capable of deflecting light waves owing to their pseudo gravity caused by lattice distortion. They experimentally verified the phenomenon in the terahertz range using a silicon DPC. Pseudo gravity caused by lattice distortion revealed alternative approaches to achieve on-chip trajectory control of light propagation in PCs. Their work has far-reaching implications for the world of optics and materials science, and bear significance for the development of 6G communications… read more. TECHNICAL […]
Category Archives: Light
Generating circularly polarised light
Nanowerk October 5, 2023 Hybrid perovskite semiconductor materials are predicted to lock chirality into place and encode asymmetry into their electronic states, while softness of their crystal lattice accommodates lattice strain to maintain high crystal quality with low defect densities. An international team of researchers (Germany, France, USA – Harvard University) has reported photoluminescence quantum efficiencies as high as 39% and degrees of circularly polarized photoluminescence of up to 52%, at room temperature, in the chiral layered hybrid lead-halide perovskites. Using transient chiroptical spectroscopy, they explained the photoluminescence yields from suppression of nonradiative loss channels and high rates of radiative […]
Curving light in a record-setting way
Phys.org September 27, 2023 Materials with large birefringence are sought after for polarization control, nonlinear optics, micromanipulation, and as a platform for unconventional light–matter coupling, such as hyperbolic phonon polaritons. Layered 2D materials can feature some of the largest optical anisotropy; however, their use in most optical systems is limited because their optical axis is out of the plane of the layers and the layers are weakly attached. A team of researchers in the US (University of Wisconsin, Washington University, University of Southern California, Oak Ridge National Laboratory, Lawrence Berkeley National Laboratory) demonstrated that a bulk crystal with subtle periodic […]
Material would allow users to ‘tune’ windows to block targeted wavelengths of light
Phys.org September 26, 2023 Dual-band electrochromism, the independent modulation of visible and near-infrared light by a single material, is highly desirable for smart windows to enhance the energy efficiency of buildings. Tungsten oxides are commercially important electrochromic materials, exhibiting reversible visible and near-infrared absorption when electrochemically reduced in an electrolyte containing small cations or protons. The presence of structural water in tungsten oxides has been associated with faster electrochromic switching speeds. A team of researchers in the US (North Carolina State University, UT Austin, Vanderbilt University) found that WO3·H2O, a crystalline hydrate, exhibited dual-band electrochromism unlike the anhydrous WO3. Making […]
Making the invisible, visible: New method makes mid-infrared light detectable at room temperature
Phys.org August 28, 2023 Existing technologies for room-temperature detection of molecular vibrations in the mid-infrared rely on cooled semiconductor detectors because of thermal noise limitations. Researchers in the UK exploited molecular emitters possessing both MIR and visible transitions from molecular vibrations and electronic states, coupled through Franck–Condon factors. By assembling molecules into a plasmonic nanocavity resonant at both MIR and visible wavelengths, and optically pumping them below the electronic absorption band, they showed transduction of MIR light. The upconverted signal was observed as enhanced visible luminescence. Combining visible luminescence with enhanced rates of vibrational pumping gave transduction efficiencies of >10%. […]
Shrinking light: Waveguiding scheme enables highly confined subnanometer optical fields
Phys.org July 17, 2023 Researchers in China developed an optical waveguide scheme to generate a sub-nanometer-confined optical field in a nano slit waveguiding mode in a coupled nanowire pair (CNP). They showed that, when a conventional waveguide mode with a proper polarization was evanescently coupled into a properly designed CNP with a central nano slit, it could be channeled into a high-purity nano slit mode within a waveguiding length <10 μm. The CNP could be either freestanding or on-chip by using a tapered fiber or planar waveguide for input-coupling, with a coupling efficiency up to 95%. Within the slit region, […]
New breakthrough shows how short pulses of light destroy particles
Phys.org July 6, 2023 Molecular polaritons are hybrid light-matter states that emerge when a molecular transition strongly interacts with photons in a resonator. At optical frequencies, this interaction unlocks a way to explore and control new chemical phenomena at the nanoscale. However achieving such control at ultrafast timescales is challenging as it requires a deep understanding of the dynamics of the collectively coupled molecular excitation and the light modes. An international team of researchers (Germany, Italy, Sweden, Spain, Luxembourg) investigated the dynamics of collective polariton states, realized by coupling molecular photoswitches to optically anisotropic plasmonic nanoantennas. Pump-probe experiments revealed an […]
Researchers create antenna for nanoscale light sources using unusual placement of semiconductor material
Phys.org July 3, 2023 Two-dimensional van der Waals materials are an excellent platform for the study of materials with well-defined interfaces. Signatures of acoustic phonons and defect states have been observed in current-to-voltage measurements. These features can be explained by direct electron–phonon or electron–defect interactions. An international team of researchers (Switzerland, Spain, Japan) used a tunnelling process that involved excitons in transition metal dichalcogenides (TMDs). They studied the tunnel junctions consisting of graphene and gold electrodes separated by hexagonal boron nitride with an adjacent TMD monolayer and observed prominent resonant features in current-to-voltage measurements appearing at bias voltages that corresponded […]
New research on self-locking light sources presents opportunities for quantum technologies
Nanowerk June 19, 2023 An international team of researchers (Argentina, Germany) demonstrated that light emitters with different resonance frequencies can asynchronously self-lock their relative energies by exchanging mechanical energy. They introduced polaromechanical metamaterials, two-dimensional arrays of μm-sized traps confining zero-dimensional light-matter polariton fluids and GHz phonons. A strong exciton-mediated polariton-phonon interaction induced a time-dependent inter-site polariton coupling J(t) with remarkable consequences for the dynamics. When locally perturbed by continuous wave optical excitation, a mechanical self-oscillation started and polaritons responded by locking the energy detuning between neighbor sites at integer multiples of the phonon energy showing asynchronous locking involving the polariton […]
New approach to developing efficient, high-precision 3D light shapers
Phys.org April 22, 2023 Specifically tailored refractive index of light modifications, directly manufactured inside glass using a short pulsed laser, enable an almost arbitrary control of the light flow. However, the stringent requirements for quantitative knowledge of these modifications, as well as for fabrication precision, have so far prevented the fabrication of light-efficient aperiodic photonic volume elements (APVEs). An international team of researchers (Austria, Germany, UK) has developed a powerful approach to the design and manufacturing of light-efficient APVEs. They optimized application-specific three-dimensional arrangements of hundreds of thousands of microscopic voxels and manufactured them using femtosecond direct laser writing inside […]