Phys.org November 23, 2022 Combinatorial problems arising in puzzles, origami, and (meta) material design have rare sets of solutions, which define complex and sharply delineated boundaries in configuration space. The boundaries are difficult to capture with conventional statistical and numerical methods. Researchers in the Netherlands have shown that convolutional neural networks can learn to recognize these boundaries for combinatorial mechanical metamaterials, down to the finest detail, despite using heavily undersampled training sets, and can successfully generalize. According to the researchers even if machine learning is typically a “black box” approach, it can still be very valuable for exploring the design […]
Tag Archives: Metamaterials
Zero-index metamaterials offer new insights into the foundations of quantum mechanics
Phys.org April 27, 2022 Most theoretical derivations of fundamental radiative processes rely on energetic considerations and detailed balance equations, but not on momentum considerations. An international team of researchers (USA – Harvard University, University of Pennsylvania, Belgium, Spain, Denmark) re-examined the foundations of quantum physics from the perspective of momentum and explored what happens when the momentum of light is reduced to zero. They theoretically demonstrated that momentum recoil, transfer momentum from the field to the atom and Doppler shift are inhibited in NZI materials. Fundamental radiative processes inhibition is also explained due to those momentum considerations inside three-dimensional NZI […]
A nanoscale 3D structure to control light
Phys.org February 2, 2022 Metamaterials can be engineered to produce desired interactions with light or sound waves. However, functionality of the devices can be limited by the corresponding design space. A team of researchers in the US (Pennsylvania State University, Sandia National Laboratory) leveraged a combination of a genetic algorithm (GA) based optimization method and a membrane projection lithography (MPL) fabrication approach, to demonstrate a quasi-3D metamaterial for broadband asymmetric transmission (AT) of linearly polarized mid-infrared light. An efficient exploration of 3D plasmonic meta-atoms with broken mirror symmetry in the light propagation direction allows the satisfaction of the rigorous conditions […]
Metasurfaces control polarized light at will
Phys.org August 14, 2021 A team of researchers in the US (Harvard University, industry) has proposed a new class of computer-generated holograms, called Jones matrix holograms, whose far-fields have designer-specified polarization response. They have provided a simple procedure for their implementation using form-birefringent metasurfaces. Jones matrix holography generalizes past work with a consistent mathematical framework, particularly in the field of metasurfaces. They have demonstrated holograms whose far-fields implement parallel polarization analysis and custom waveplate-like behavior. The new approach could lead to applications in diverse fields including imaging, microscopes, displays, and astronomy. The work shows that the ability to switch between […]
New type of metasurface allows unprecedented laser control
Phys.org June 29, 2021 An international team of researchers (USA – Harvard University, Italy) has developed a tunable laser that has two components—a laser diode and a reflective metasurface. The metasurface surface uses supercells, groups of pillars which work together to control different aspects of light. It is designed so that only the selected wavelength has the correct direction to enter back in the diode enabling the laser to operate only at that specific wavelength. The wavelength can be changed by moving the metasurface with respect to the laser diode. The shape of the laser beam can be fully controlled […]
Novel materials: Sound waves traveling backwards
Nanowerk June 10, 2021 Acoustic waves in gases, liquids, and solids usually travel at an almost constant speed of sound. However, rotons, quasiparticles, are an exception: their speed of sound changes significantly with the wavelength, and it is also possible that the waves travel backwards. Rotons were predicted in 1962 in the context of superfluidity. Until now, they could only be observed under special quantum-physical conditions at very low temperatures – and were therefore not suitable to technical applications. An international team of researchers (Germany, France) propose an artificial material that can produce rotons without any quantum effects under normal […]
One material, two functionalities
Nanowerk May 25, 2021 Flexible metamaterials often harness zero-energy deformation modes. To date they have a single property, such as a single shape change, or are pluripotent. An international team of researchers (the Netherlands, Switzerland) has introduced a class of oligomodal metamaterials that encode a few distinct properties that can be selectively controlled under uniaxial compression. They demonstrated this concept by introducing a combinatorial design space containing various families of metamaterials. They included monomodal (with a single zero-energy deformation mode); oligomodal (with a constant number of zero-energy deformation modes); and plurimodal (with many zero-energy deformation modes), whose number increases with system […]
Team creates new ultralightweight, crush-resistant tensegrity metamaterials
Phys.org March 11, 2021 Catastrophic collapse of materials and structures is the inevitable consequence of a chain reaction of locally confined damage. A-team of researchers in the US (UC Irvine, Georgia Institute of Technology) created mechanical metamaterials that delocalize deformations to prevent failure. They used direct laser writing technique to generate elementary cells sized between 10 and 20 microns which were built up into eight-unit supercells that could be assembled with others to make a continuous structure. They showed that failure resistance is up to 25‐fold enhancement in deformability and orders of magnitude increased energy absorption capability without failure over […]
Physics discovery leads to ballistic optical materials
Nanowerk December 14, 2020 The mismatch between electronic systems and optical systems means that every time a signal converts from one to the other, inefficiency creeps into the system. A team of researchers in the US (UT Austin, UMass Lowell, Purdue University) has found a way to create more efficient metamaterials using semiconductors and a novel aspect of physics that amplifies the activity of electrons. They have demonstrated optical phenomenon of “ballistic resonance” resulting from the interplay between free charge motion in confining geometries and periodic driving electromagnetic fields, which can be utilized to achieve negative permittivity at frequencies well […]
Topological mechanical metamaterials go beyond Newton’s third law
Phys.org November 19, 2020 An international team of researchers (Israel, Los Alamos) found a way to mimic non-Newtonian behavior in mechanical systems, and thereby develop a mechanical implementation for some of the more intractable topological quantum systems, which may offer fundamentally new insights into both the mechanical and quantum topological systems. The unit cells in a mechanical lattice are subjected to active feedback forces that are processed through autonomous controllers, pre-programmed to generate the desired local response in real-time. They demonstrated that the required topological phase, characterized by chiral edge modes, can be achieved in an analogous mechanical system only […]