Photonic metasurfaces provide a new playground for twistronics

Phys.org  April 27, 2020 Hyperbolic metasurfaces (HMTSs) are known to support confined surface waves collimated toward specific directions determined by the metasurface dispersion. By rotating two evanescently coupled HMTSs with respect to one another, an international team of researchers (USA – University of New York, UT Austin, Singapore) unveil rich dispersion engineering, topological transitions at magic angles, broadband field canalization, and plasmon spin-Hall phenomena. These findings open remarkable opportunities to advance metasurface optics, enriching it with moiré physics and twistronic concepts…read more. TECHNICAL ARRTICLE

First bufferless lasers grown directly on silicon wafers in Si-photonics

Nanowerk  March 4, 2020 In conventional approaches of integrating III-V lasers on Si thick III-V buffers up to a few micrometers are used to reduce the defect densities, which posses huge challenges for efficient light interfacing between the epitaxial III-V lasers and the Si-based waveguides. Based on numerical simulations an international team of researchers (China, Hong Kong) designed and fabricated a novel growth scheme to eliminate the requirement of thick III-V buffers and thus promoted efficient light coupling into the Si-waveguides. They demonstrated the 1.5 µm III-V lasers directly grown on the industry-standard 220 nm SOI wafers using metal organic […]

Researchers create new state of light

Phys.org  February 25, 2020 Light rotates around a longitudinal axis parallel to the direction light travels. An international team of researchers (China, USA – University of Dayton) has demonstrated a three-dimensional wave packet that is a spatiotemporal (ST) optical vortex with a controllable purely transverse orbital angular momentum (OAM). The magnitude of the transverse OAM carried by the ST vortex is scalable to a larger value by simple adjustments. Since the ST vortex carries a controllable OAM uniquely in the transverse dimension, it has strong potential for novel applications that may not be possible otherwise. The scheme reported here can […]

Using light to put a twist on electrons

Science Daily  February 26, 2020 Chirality occurs not in the structure of the molecules themselves, but in a kind of patterning in the density of electrons within the material. An international team of researchers (USA – MIT, Carnegie Mellon, Northeastern University, Cornell University, Drexel University, Taiwan, Singapore, Japan) found that while titanium diselenide at room temperature has no chirality to it, as its temperature decreases it reaches a critical point where the balance of right-handed and left-handed electronic configurations gets thrown off and one type begins to dominate. They found that this effect could be controlled and enhanced by shining […]

What if we could teach photons to behave like electrons?

Phys.org  February 19, 2020 An international team of researchers (USA – Stanford University, China) tricked the photons—which are intrinsically non-magnetic—into behaving like charged electrons by sending the photons through carefully designed mazes in a way that caused the light particles to behave as if they were being acted upon by what the scientists called a “synthetic” or “artificial” magnetic field. They designed structures that created magnetic forces capable of pushing photons in predictable and useful ways. To bring photons into the proximities required to create these magnetic effects, the researchers used lasers, fiber optic cables and other off-the-shelf scientific equipment. […]

If you want to catch more light, twist it

Nanowerk  January 31, 2020 The bulk photovoltaic effect is a way to convert light into electrical current. An international team of researchers (USA – Boston College, UCLA, Germany, Switzerland) developed microscopic devices based on the Weyl semimetal tantalum arsenide. They had larger bulk photovoltaic effect than seen before. The devices they developed absorbed mid-infrared light, an important wavelength for devices that conduct chemical and thermal imaging as well as waste heat recovery. The observed magnitude and wavelength range of the shift current advances our fundamental understanding of the effects of topology in materials. It also demonstrates the utility of Weyl […]

Converting absorbed photons into twice as many excitons

Science Daily  September 24, 2019 An international team of researchers (Japan, Finland) found that when light was exposed to the surface of a tetracene alkanethiol-modified gold nanocluster, they were able to convert singlet oxygen at a highly efficient conversion rate of 160%, far exceeding 100% conversion, in comparison to the number of absorbed photons. An increase in lifetime of about 10,000 times was achieved by greatly suppressing the rapid loss of excitation energy on the metal surface. These findings are expected to contribute to areas such as solar energy conversion, electronics, life sciences, and medical care in the future…read more. […]

Engineers using soundwaves to search through big data with more stability and ease

Phys.org  September 19, 2019 Using three aluminum rods, enough epoxy to connect them and some rubber bands for elasticity researchers at the University of Arizona have demonstrated the possibility for acoustic waves in a classical environment to do the work of quantum information processing without the time limitations and fragility. They sent a wave of sound vibrations down the rods, then monitored two degrees of freedom of the waves: what direction the waves moved down the rods and how the rods moved in relation to one another. To excite the system into a nonseparable state, they identified a frequency at […]

Light Seems to Pull Electrons Backward

American Physical Society Focus  August 2, 2019 It is long assumed that light hitting a metal surface at an angle pushes on the free electrons, moving them forward. A team of researchers in the US (NIST, University of Maryland, Brown University) aimed an infrared laser toward the metal surface at a glancing angle and placed an electrode at the far end of the metal sample to detect any voltage created if the light drove the electrons along the metal, which would create an excess of negative charge at the far end. As they varied the angle, the team measured a […]

New property of light discovered

Phys.org   June 28, 2019 An international team of researchers (Spain, USA – University of Colorado) has discovered a new property of light—self-torque. Their experiments involved firing two lasers at a cloud of argon gas—doing so forced the beams to overlap, and they joined and were emitted as a single beam from the other side of the argon cloud. The result was a type of vortex beam. Then they changed the the orbitatl momentum so that the lasers had different orbital angular momentum and they were slightly out of sync. This resulted in a beam that looked like a corkscrew with […]