Phys.org March 11, 2024 Metasurfaces are candidates for vectorial optics polarization, but their static post-fabrication geometry largely limits dynamic tunability. Liquid crystal (LC) is usually employed as an additional index-changing layer together with metasurfaces. However, most of the reported LCs only impart a varying but uniform phase on top of that from the metasurface. An international team of researchers (China, Singapore) pixelated a single-layer LC to display versatile and tunable vectorial holography, in which the polarization and amplitude could be arbitrarily and independently controlled at varying spatial positions. The subtle and vectorial LC-holography highlighted the broadband and electrically switchable functionalities. […]
Tag Archives: Optics
In a new light – new approach overcomes long-standing limitations in optics
Nanowerk December 12, 2023 The canonical studies on Mie scattering unravel strong electric/magnetic optical responses in nanostructures, laying foundation for emerging meta-photonic applications. Conventionally, the morphology-sensitive resonances hinge on the normalized frequency, i.e. particle size over wavelength, but non-paraxial incidence symmetry is overlooked. Through confocal reflection microscopy with a tight focus scanning over silicon nanostructures, an international team of researchers (Taiwan, Japan, China) showed the scattering point spread functions’ distinctive spatial patterns featuring linear scattering efficiency was maximal when the focus was misaligned. The underlying physical mechanism was the excitation of higher-order multipolar modes, not accessible by plane wave irradiation, […]
A new strategy for active metasurface design provides a full 360-degree phase tunable metasurface
Phys.org May 2, 2022 Active metasurfaces have been proposed as one attractive means of achieving high-resolution spatiotemporal control of optical wavefronts, having applications such as LIDAR and dynamic holography. An international team of researchers (South Korea, USA – University of Wisconsin) has developed an electrically tunable metasurface design strategy that operates near the avoided crossing of two resonances, one a spectrally narrow, over-coupled resonance and the other with a high resonance frequency tunability. It displayed an upper limit of 4π range of dynamic phase modulation with no significant variations in optical amplitude, by enhancing the phase tunability through utilizing two […]
Fingers made of laser light: Controlled grabbing and rotation of biological micro-objects
Science Daily December 23, 2021 Although optical trapping forces are strong enough and related photodamage is acceptable, the precise (re-) orientation of large specimen with multiple optical traps is difficult, since they grab blindly at the object and often slip off. Researchers in Germany have developed an approach to localize and track regions with increased refractive index using several holographic optical traps with a single camera in an off-focus position. They estimated the 3D grabbing positions around several trapping foci in parallel through analysis of the beam deformations, which are continuously measured by defocused camera images of cellular structures inside […]
Tiny chip provides a big boost in precision optics
Phys.org November 12, 2021 Based on a theory of weak value amplification with waveguides, a team of researchers in the US (University of Rochester, industry, Chapman University) has packaged an experimental way of amplifying interferometric signals—without a corresponding increase in noise —on a 1 mm by 1 mm integrated photonic chip. Weak value amplification is based on the quantum mechanics of light, and basically involves directing only certain photons that contain the information needed, to a detector. They distilled all of this and put it into a photonic chip. The device removes that limitation of traditional interferometers by reaching the […]
Ultra-strong squeezing of light demonstrated for ultrafast optical signal processing
Phys.org July 6, 2021 An international team of researchers (Singapore, USA – MIT) succeeded in squeezing light in time by a factor of 11. They demonstrated 3.0× spectral compression of 480 fs pulses while preserving the pulse energy. The strong compression achieved at low powers harnesses advanced on-chip device design, and the strong nonlinear properties of backend-CMOS compatible ultra-silicon-rich nitride, which possesses absence of two-photon absorption and 500× larger nonlinear parameter than in stoichiometric silicon nitride waveguides. By balancing the contributions from the dispersive and nonlinear stages, they could generate strong compression in either time or frequency. The work introduces an […]
Cameras and telescopes as thin as a sheet of paper?
Nanowerk June 10, 2021 Metalenses promise to make imaging devices more compact. An international team of researchers (Canada, USA – University of Rochester) has addressed the space between the lenses which is crucial for image formation but takes up by far the most room in imaging systems, by introducing the idea of a spaceplate. They experimentally demonstrated that it is compatible with broadband light in the visible spectrum. They manipulated light based on the angle rather than the position of a light ray. Angle is a completely novel domain. They designed and experimentally demonstrated plates that compressed the space. Such […]
Trapping light without back reflections
Phys.org January 4, 2021 Due to material imperfections, some amount of light is reflected backwards in microresonators which disturbs their function. To reduce the unwanted backscattering an international team of researchers (UK, Germany) used the principle of noise cancelling headphone and introduced out-of-phase light to cancel out optical interference. To generate the out-of-phase light, the researchers position a sharp metal tip close to the microresonator surface. The tip also causes light to scatter backwards. As the phase of the reflected light can be chosen by controlling the position of the tip, backscattered light’s phase can be set so it annihilates […]
Cartwheeling light reveals new optical phenomenon
Nanowerk June 29, 2020 While there are numerous forms of light polarization, only linear and circular polarizations, which have wave motion in a flat sheet or helix, respectively, are typically used. A team of researchers in the US (Rice University, UMass Dartmouth) utilized trochoidal polarizations with cartwheeling wave motion. They demonstrated that single gold nanorod dimers can discriminate between trochoidal fields rotating in opposite directions, which they named trochoidal dichroism. Trochoidal dichroism forms an additional classification of polarized light–matter interaction and could inspire the development of optical studies uniquely sensitive to molecules with cartwheeling charge motion, potentially relevant for probing […]
New water-based optical device revolutionizes the field of optics research
Phys.org November 20, 2019 Researchers in Japan have developed a light modulator using the Pockels effect of water in a nanometer-thick electric double layer on an electrode surface. The modulator comprises a transparent-oxide electrode on a glass substrate immersed in an aqueous electrolyte solution. When an optical beam is incident such that it is totally reflected at the electrode-water interface, the light is modulated at a specific wavelength with a near-100% modulation depth synchronized with the frequency of the applied AC voltage. Pockels effect has applications in optical engineering, optical communication, displays and electric sensors and the enhancement principle opens […]