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 […]
Tag Archives: Metamaterials
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 […]
New photonics breakthrough
Science Daily December 13, 2019 An international team of researchers (USA – City College of New York, Russia) has shown that long-range interactions in the metamaterial changes the common behavior of light waves forcing them to localize in space. The study shows that by controlling the degree of such interactions one can switch between trapped and extended (propagating) character of optical waves. The new approach to trap light allows the design of new types of optical resonators, which may have significant impact on antennas in smartphones and Wi-Fi routers, and optical chips in optoelectronics used for transferring data over the […]
Researchers develop ‘acoustic metamaterial’ that cancels sound
Phys.org March 7, 2019 Based on the premise that metamaterial needs to be shaped in such a way that it sends incoming sounds back to where they came from, researchers at Boston University calculated the dimensions and specifications that the metamaterial would need to have in order to interfere with the transmitted sound waves. Using the calculation they created a structure made of plastic that could silence sound from a loudspeaker. In tests they found that 94 percent of the sound emanating from the loudspeaker was imperceptible to the human ear. The shape of acoustic-silencing metamaterials is also completely customizable. […]
‘Meta-mirror’ reflects sound waves in any direction
Science Daily March 7, 2019 To break the law of reflection with sound waves, an international team of researchers (Finland, USA – Duke University) designed a meta-mirror out of plastic with precisely etched channels on the surface of the metamaterial. Between the meta-mirror’s shape and the depth of its channels, the interference pattern results in the sound wave reflecting in a desired direction without any of its energy being absorbed or scattered in an unwanted direction. In demonstration the device reflected a soundwave traveling directly toward it at 3,000 Hertz and perfectly reflects it at an angle of 70 degrees. […]