Research team discovers two-dimensional waveguides

Phys.org  February 15, 2024 A team of researchers in the US (US Naval Research Laboratory, Kansas State University) demonstrated how hexagonal boron nitride (hBN) slabs tuned to the correct thickness act as optical waveguides, enabling direct optical coupling of light emission from encapsulated layers into waveguide modes. They integrated molybdenum selenide (MoSe2) and tungsten selenide (WSe2) within hBN-based waveguides and demonstrated direct coupling of photoluminescence emitted by in-plane and out-of-plane transition dipoles (bright and dark excitons) to slab waveguide modes. They demonstrated that dry etched hBN edges are an effective out-coupler of waveguided light without the need for oil-immersion optics. […]

Scientists invent smallest known way to guide light

Science Daily  August 11, 2023 Addressing the optical mismatch between components typically results in compromises in size and performance of chip-scale optical circuits for practical devices. Researchers at the University of Chicago showed that they could confine and guide light in an ultrathin two-dimensional (2D) material (<1 nanometer thick). They made three-atom-thick waveguides—δ waveguides—based on wafer-scale molybdenum disulfide (MoS2) monolayers that could guide visible and near-infrared light over millimeter-scale distances with low loss and an efficient in-coupling. The extreme thinness provided a light-trapping mechanism analogous to a δ-potential well in quantum mechanics and enabled the guided waves that were essentially […]

Researchers realize complete family of logic gates using silicon-on-silica waveguides at 1.55 μm

Phys.org  February 13, 2023 An international team of researchers (China, Greece) employed silicon-on-silica waveguides for the all-optical realization of a complete family of logic gates, including NOT, XOR, AND, OR, NOR, NAND and XNOR operated at 1.55 μm. The waveguide consists of three identical slots and six microring resonators, all made of silicon patterned on silica. The principle of operation of these logic gates was based on the constructive and destructive interference induced by the phase difference between the input signals. The gates’ performance is evaluated against the contrast ratio (CR) metric. According to the researchers, compared to existing waveguides, […]

Topological acoustic waveguide to help reduce unwanted energy consumption in electronics

Pays.org  January 30, 2023 Researchers in Japan have shown that in a honeycomb phononic crystal composed of metallic nanopillars on a LiNbO3 substrate, the topological surface acoustic wave (SAW) mode inhabits the edge of the honeycomb phononic crystal in spite of the hybridization with the internal acoustic modes of the substrate. Pulse-type microwave impedance microscopy showed gigahertz topological edge mode between two mutually inverted topological phononic crystals. A frequency-dependent image showed that the edge mode evolves as the bulk SAW modes are suppressed owing to the energy gap formation, consistent with the topological nature. According to researchers the realization of a […]

Controlling non-classical mechanical states in a phononic waveguide architecture

Phys.org  June 24, 2022 Researchers in the Netherlands used a cavity–waveguide architecture, where the cavity is used as a source and detector for the mechanical excitations while the waveguide has a free-standing end to reflect the phonons. This enabled them to observe multiple round trips of phonons between the source and the reflector. The long mechanical lifetime of almost 100 μs demonstrated the possibility of nearly lossless transmission of single phonons over tens of centimetres. Their experiment demonstrated full on-chip control over travelling single phonons strongly confined in the direction transverse to the propagation axis, potentially enabling a time-encoded multimode quantum […]

Silicon waveguides move us closer to faster, light-based logic circuits

Phys.org  February 8, 2021 Wiring up the transistors of an optical circuit with silicon waveguides is an important requirement to make compact, highly integrated chips. However, silicon is a strong absorber of visible light. To circumvent the absorption issue researchers in Switzerland used high contrast grating consisting of nanometer sized “posts” lined up in such a way that light passing through the posts interferes destructively with light passing between posts making sure that no light can “leak” through the grating. Most of the light gets reflected inside the waveguide. They showed that there was a loss of only 13 percent […]

Sculpting a Waveguide with Light

American Physical Society August 14, 2020 Accelerating charged particles using intense laser pulses instead of radio-frequency fields could dramatically reduce the sizes of high-energy particle accelerators. Researchers at the University of Maryland prepared a longer, more controllable, and less leaky waveguide using two consecutive laser pulses that approximate Bessel beams, which are waveforms that do not spread out as they propagate. The first pulse creates the core of the waveguide. The second pulse creates the cladding. With this independent preparation of core and cladding, the team could form a waveguide with finely tunable parameters, such as the diameter and the […]

A Graphene Waveguide For Electrons

American physical Society  November 22, 2019 An electron carrying information in its quantum state and acting according to its wave nature can travel though a waveguide, but if multiple modes are available, then the electron can switch between them and lose information. An international team of researchers (USA – MIT, Japan, France) designed a device that includes a graphene flake sandwiched between two insulating sheets. On top of this structure sits a single carbon nanotube. A voltage applied across the CNT induces an electrostatic potential shaped like a rain gutter that extends down into the flake. The potential traps the […]

Thinnest optical waveguide channels light within just three layers of atoms

Science Daily  August 12, 2019 A team of researchers in the US (UC San Diego, City University of New York, Johns Hopkins University) present an experimental demonstration of light guiding in an atomically thick tungsten disulfide membrane patterned as a photonic crystal structure. In this scheme, two-dimensional tungsten disulfide excitonic photoluminescence couples into quasi-guided photonic crystal modes known as resonant-type Wood’s anomalies. These modes propagate via total internal reflection with only a small portion of the light diffracted to the far field. Such light guiding at the ultimate limit provides more possibilities to miniaturize optoelectronic devices and to test fundamental […]