Phys.org December 16, 2024 Conventional methods used to produce these microparticle components frequently offer limited control of their structural properties or require low-throughput nanofabrication of more complex structures. An international team of researchers (USA – University of Rochester, University of Colorado, the Netherlands) used a synthetic biology approach to produce environmentally friendly, living microlenses with tunable structural properties. They engineered Escherichia coli bacteria to display the silica biomineralization enzyme silicate from aquatic sea sponges which could self-assemble a shell of polysilicate “bioglass” around themselves. The bacteria could focus light into intense nanojets that were nearly an order of magnitude brighter […]
Tag Archives: Optics
Physicists reveal how layers and twists impact graphene’s optical conductivity
Phys.org November , 2024 An international team of researchers (USA – Florida State University, China) explored the advantages of moiré superlattices in twisted bilayer graphene (TBG) aligned with hexagonal boron nitride (hBN) for passively enhancing optical conductivity in the low-energy regime. To probe the local optical response of TBG/hBN double-moiré lattices, they used infrared nano-imaging in conjunction with nanocurrent imaging to examine local optical conductivity over a wide range of TBG twist angles. They showed that interband transitions associated with the multiple moiré flat and dispersive bands produced tunable transparent IR responses even at finite carrier densities, which is in […]
Cloud-inspired method of guiding light: Waveguiding mechanism could provide new ways to look inside the human body
Phys.org November 1, 2024 The guiding and transport of energy, for example, of electromagnetic waves, underpins many modern technologies, ranging from long-distance optical fibre telecommunications to on-chip optical processors. It requires localizing the waves or particles in the confinement region, such as total internal reflection at a boundary. An international team of researchers (UK, USA – University of Arizona) introduced a waveguiding mechanism that relies on a different origin for the exponential confinement and that arises owing to the physics of diffusion. They demonstrated this concept using light and showed that the photon density could propagate as a guided mode […]
Pyramid optical networks for unidirectional image magnification and demagnification
Phys.org August 1, 2024 Researchers at UC California developed a pyramid-structured diffractive optical network design (P-D2NN), optimized specifically for unidirectional image magnification and demagnification. The diffractive layers were pyramidally scaled in alignment with the direction of the image magnification or demagnification, to inhibit image formation in the opposite direction, thus achieved the desired unidirectional imaging operation using a much smaller number of diffractive degrees of freedom within the optical processor volume. The design maintained its unidirectional image magnification/demagnification functionality across a large band of illumination wavelengths. It allowed a unidirectional magnifier and a unidirectional demagnifier operation simultaneously in opposite directions, […]
Novel method for controlling light polarization uses liquid crystals to create holograms
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. […]
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 […]