Phys.org October 11, 2024 Researchers in Japan visualized antiferromagnetic domains in a representative quasi-one-dimensional antiferromagnet using nonreciprocal directional dichroism, which differentiated the optical absorption of a pair of antiferromagnetic domains. Opposite antiferromagnetic domains, each about submillimeter in size, were found to coexist in a single-crystal specimen, and the domain walls ran predominantly along the spin chains. They showed that the domain walls could be moved by an applied electric field through a magnetoelectric coupling, and the direction of the domain walls was maintained during the motion. They explained the domain wall anisotropy by the quasi-one-dimensional nature of the exchange interactions. […]
Tag Archives: Light
Electrically modulated light antenna points the way to faster computer chips
Phys.org September 9, 2024 Because of the quantum nature of electrons, real interfaces have finite thickness, leading to nonclassical surface effects that influence light scattering in small particles. Electrical gating offers a promising route to control and study these effects, as static screening charges reside at the boundary. An international team of researchers (Germany, Denmark) investigated the modulation of the surface response upon direct electrical charging of single plasmonic nanoresonators. By analyzing measured changes in light scattering within the framework of surface response functions, they found the resonance shift well accounted for by modulation of the classical in-plane surface current. […]
A chip-scale titanium-sapphire laser
Nanowerk June 26, 2024 Ti:sapphire lasers are unmatched in bandwidth and tuning range, yet their use is restricted because of their large size, cost and need for high optical pump powers. An international team of researchers (USA – Stanford University, Belgium) demonstrated a monocrystalline titanium:sapphire-on-insulator (Ti:SaOI) photonics platform that enabled dramatic miniaturization, cost reduction and scalability of Ti:sapphire technology. Through the fabrication of low-loss whispering-gallery-mode resonators, they realized a Ti:sapphire laser operating with an ultralow, sub-milliwatt lasing threshold; through orders-of-magnitude improvement in mode confinement in Ti:SaOI waveguides, they realized an integrated solid-state optical amplifier operating below 1 μm. They amplified distortion-free […]
Controlling electronics with light: the magnetite breakthrough
Nanowerk June 21, 2024 Symmetry breaking across phase transitions often causes changes in selection rules and emergence of optical modes which can be detected via spectroscopic techniques or generated coherently in pump-probe experiments. An international team of researchers (Switzerland, Poland, Czech Republic, Italy) demonstrated that in magnetite (Fe3O4) light excitation coupled to the critical fluctuations of the charge order and coherently generated structural modes of the ordered phase above the critical temperature of the Verwey transition. According to the researchers their methodology represents an effective tool to study the real-time dynamics of critical fluctuations across phase transitions… read more. TECHNICAL […]
Custom-made molecules designed to be invisible while absorbing near-infrared light
Nanowerk June 17, 2024 Molecules that can absorb near-infrared light but not visible light have applications in everything from chemotherapy to photodetectors. Researchers in Japan were able to systematically design a large, complex molecule that does not absorb visible light, (it is completely colorless and transparent) but absorbs near-infrared radiation by carefully constructing molecules that have suitable arrangements of electrons. It showed an absorption band in the NIR region without distinct visible-light absorption, which has led to the establishment of colorless characteristics. Theoretical analyses indicated that the combination of a polyene-like electronic structure with orbital symmetry was important to obtain […]
Physicists reach atomic-scale telegraphy with light
Phys.org May 8, 2024 By exploiting linear interaction with tip-confined evanescent light fields, near-field microscopy has reached even higher resolution, prompting a vibrant research field by exploring the nanocosm in motion. Yet the finite radius of the nanometre-sized tip apex has prevented access to atomic resolution. Researchers in Germany leveraged extreme atomic nonlinearities within tip-confined evanescent fields to push all-optical microscopy to picometric spatial and femtosecond temporal resolution. They discovered an unprecedented and efficient non-classical near-field response, in phase with the vector potential of light and strictly confined to atomic dimensions. This ultrafast signal was characterized by an optical phase […]
Research team discovers new property of light
Phys.org May 7, 2024 The nature of enhanced photoemission in disordered and amorphous solids is an intriguing question. An international team of researchers (Russia, USA – UC Irvine) studied structural photoemission in heterogeneous cross-linked silicon glass, a material that represents an intermediate state between the amorphous and crystalline phases, characterized by a narrow distribution of structure sizes. The model system showed a clear dependence of photoemission on size and disorder across a broad range of energies. While phonon-assisted indirect optical transitions are insufficient to describe observable emissions, their experiments suggested these could be understood through electronic Raman scattering. They attributed […]
Researchers control quantum properties of 2D materials with tailored light
Phys.org April 15, 2024 The stacking and twisting of atom-thin structures with matching crystal symmetry has provided a unique way to create new superlattice structures in which new properties emerge. An international team of researchers (Germany, Spain, USA – SLAC National Accelerator Laboratory, Stanford University) demonstrated a tailored light-wave-driven analogue to twisted layer stacking. Tailoring the spatial symmetry of the light waveform to that of the lattice of a hexagonal boron nitride monolayer and then twisting this waveform resulted in optical control of time-reversal symmetry breaking and the realization of the topological Haldane model in a laser-dressed two-dimensional insulating crystal. […]
Light and sound waves reveal negative pressure
Phys.org September 25, 2023 Pressure is encountered in various fields – atmospheric pressure in meteorology, blood pressure in medicine, etc. Examining the physical properties of materials under a wide range of thermodynamic states is a challenging problem due to the extreme conditions the material must experience. Such temperature and pressure regimes, which result in a change in the refractive index and sound velocity, can be accessed by optoacoustic interactions such as Brillouin–Mandelstam scattering. An international team of researchers (Germany, France, Australia) demonstrated the Brillouin–Mandelstam measurements of nanolitre volumes of liquids in extreme thermodynamic regimes enabled by a fully sealed liquid-core […]
Copper-doped tungstic acid nanocrystals transform infrared light conversion
Nanowerk September 13, 2023 The technology to utilize the full spectrum of solar radiation is still in its infancy as conventional methods constrain their all-solar response. Researchers in Japan have proposed using – submerged photosynthesis of crystallites (SPsC). They showed that strategic doping with copper and oxygen vacancies can induce opto-critical phases from the non-stoichiometric tungstic acids. These opto-critical phases enabled a dynamic equilibrium shift in lattice defect stabilization, facilitating an unprecedented whole solar wavelength response. The response manifested photo-assisted water evaporation, and photo-electrochemical characteristics. According to the researchers their strategy of harnessing all-solar energy, the one-pot SPsC strategy, may […]