Scientists Slowed Down Light by 10,000 Times in an Experiment

Science Alert  February 11, 2024 The metasurface analogue of electromagnetically induced transparency (EIT) provides a chip-scale platform for achieving light delay and storage, high Q factors, and greatly enhanced optical fields. Researchers in China developed a new approach for realizing collective EIT-like bands with a measured Q factor reaching 2750 in silicon metasurfaces in the near-infrared regime. It employed the coupling between two collective resonances, the Mie electric dipole surface lattice resonance (SLR) and the out-of-plane/in-plane electric quadrupole SLR (EQ-SLR). The collective EIT-like resonance could have diverging Q factor and group delay due to the bound state in the continuum […]

Researchers use ultrasound waves to move objects hands-free

Science Daily  December 6, 2022 The transfer of wave momentum is a fundamental mechanism for contactless manipulation, yet the rules of conventional scattering intrinsically limit the radiation force based on the shape and the size of the manipulated object. Researchers at the University of Minnesota showed that this intrinsic limit can be broken for acoustic waves with subwavelength metasurfaces. Harnessing anomalous metasurface scattering, they demonstrated self-guidance, where a metasurface object is autonomously guided by an acoustic wave, and tractor beaming, where a metasurface object is pulled by the wave. According to the researchers their results show that bringing the metasurface […]

Meta-lens offers superior off-axis focus

Phys.org  October 24, 2022 After experimentally studying the optical properties of dielectric reflective metalenses including their off-axis focusing performance, researchers in Saudi Arabia proposed reflective metalens based on titanium dioxide (TiO2) and silicon dioxide (SiO2), which operate at a visible wavelength of 0.633 µm. Unlike conventional reflective metalenses based on metallic mirrors, the proposed device was designed based on a modified parabolic phase profile and was integrated onto a dielectric distributed Bragg reflector periodic structure to achieve high reflectivity with five dielectric pairs. The focusing efficiency characteristics of the metalens were experimentally studied for beam angles of incidence between 0∘ […]

New practical method of producing Airy beams could enhance ultrasound

Phys.org   September 7, 2022 Airy beams are a class of acoustic waves that move on a curved, arch-like trajectory and can auto-focus around obstacles that are directly in the beam’s path, which makes them well suited for ultrasound applications in biomedical imaging, therapy, non-destructive testing, and particle manipulation. A team of researchers in the US (Washington State University, Pennsylvania State University) has designed and fabricated a family of Airy-beam-enabled binary acoustic metasurfaces (AB BAMs) to generate Airy beams for underwater ultrasound-beam manipulation. They used 3D printing with two coding bits: a polylactic acid unit acting as a bit “1” and […]

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 […]

Metasurface enabled quantum edge detection

Phys.org  December 29, 2020 Metasurfaces consisting of engineered dielectric or metallic structures provide unique solutions to realize exotic phenomena including negative refraction, achromatic focusing, electromagnetic cloaking, and so on. The intersection of metasurface and quantum optics may lead to new opportunities but is much less explored. An international team of researchers (China, USA – UC San Diego, Columbia University, Harvard University, Austria) proposed and experimentally demonstrated that a polarization-entangled photon source can be used to switch ON or OFF the optical edge detection mode in an imaging system based on a high-efficiency dielectric metasurface. This experiment enriches both fields of […]

Metasurface opens world of polarization

Science  Daily June 3, 2020 To achieve broad polarization manipulation, multiple birefringent materials need to be stacked one top of another making these devices bulky and inefficient. Researchers at Harvard University used topological optimization to design birefringent materials. They started with the functionality of the metasurface and allowed the algorithm to explore the huge parameter space to develop a pattern that can best deliver that function. The resulting metasurface was composed of nested half circles. The odd shapes have opened a whole new world of birefringence. They can achieve broad polarization manipulations; polarization can be tuned by changing the angle […]

Smart metamaterials that sense and reprogram themselves

Phys.com  November 11, 2019 As proof of concept, an international team of researchers (USA – Duke University, UK, China) proposed and developed a smart digital-coding metasurface with self-adaptive capacity for reprogrammable functionality. A sensor on the metasurface detected specific features surrounding the construct in the environment and delivered them to a microcontroller unit (MCU) which independently determined reactions to these variations and then instructed the FPGA via coding patterns, to change the metasurface configuration in real time. The smart metasurfaces achieved self-adaptive reprogrammable functionality automatically based on the surface-installed sensing-feedback system and calculation software. The team envisions the preliminary work […]

‘Folded’ optical devices manipulate light in a new way

Phys.org October 31, 2018 In metasurface-based optical systems, most of the total volume inside the device is just free space through which light propagates between different elements. Free space makes it difficult to scale down the device. To overcome this limitation, a team of researchers in the US (Caltech, UMass Amherst) has introduced a technology called “folded metasurface optics,” which is a way of printing multiple types of metasurfaces onto either side of a substrate making the substrate itself a propagation space for the light. They demonstrated the technique by building a spectrometer. The folded metasystem design can be applied […]