Researchers create entangled photons 100 times more efficiently than previously possible

Phys.org  December 17, 2020 Current methods of creating entanglement are inefficient, requiring a torrent of incoming laser light comprising hundreds of millions of photons before a single entangled photon pair will grudgingly drip out at the other end. Based on their earlier research, researchers at the Stevens Institute of Technology carved extremely high-quality racetrack-shaped microcavities into flakes of lithium niobate crystal. The cavities internally reflect photons with very little loss of energy, enabling light to circulate longer and interact with greater efficiency. By fine-tuning additional factors such as temperature, the team was able to create an unprecedentedly bright source of […]

Research develops new theoretical approach to manipulate light

EurekAlert  December 8, 2020 Researchers in the UK re-examined the refractive index and found a general way to calculate the direction-dependent refractive index and the condition for zero index in a given direction. By analogy with linear versus circular polarization, they showed that when the zero-index direction is complex-valued, a material supports waves that can propagate in only one sense, for example, clockwise. They showed that there is an infinite family of both time-reversible and time-irreversible homogeneous electromagnetic media that support unidirectional propagation for a particular polarization. The work extends the concept of the refractive index, shedding new light on […]

Now you see it, now you don’t: Hidden colours discovered by coincidence

Phys.org  October 15, 2020 Unusual structural colors are demonstrated in thin‐film coatings due to a combination of optical interference and light scattering effects. These vivid colors are concealed under ambient illumination but can be observed when light is reflected from the film surface. An international team of researchers (Australia, China, Germany) explored the origin of the effect computationally and showed that, in thin‐films of lossless dielectrics coated on near‐perfect conductors, incident electromagnetic waves form standing waves. Electric field intensities at the thin film interfaces are maximized for wavelengths that fulfil destructive interference conditions, while nanoscale roughness can enhance scattering at […]

Intelligent nanomaterials for photonics

Science Daily  October 7, 2020 2D materials – combined with optical fibers – can enable novel applications in the areas of sensors, non-linear optics, and quantum technologies. An international team of researchers (Germany, Australia) studied the chemical vapor deposition of monolayer MoS2 and WS2 crystals on the core of microstructured exposed‐core optical fibers and their interaction with the fibers’ guided modes. Two distinct application possibilities of 2D‐functionalized waveguides to exemplify their potential are demonstrated. First, the excitonic 2D material photoluminescence is simultaneously excited and collected with the fiber modes. Then it is shown that third‐harmonic generation is modified by the highly […]

Physicists create turnstile for photons

Phys.org  September 22, 2020 If the quantum emitter is excited with laser light and fluoresces, it will always emit exactly one photon with each quantum leap. For this type of source, it is then still a challenge to efficiently “feed” the emitted photons into a glass fiber to send as many of them as possible to the receiver. An international team of researchers (Austria, Germany, Denmark) generated strongly correlated photon states using only weak coupling and taking advantage of dissipation. An ensemble of non-interacting waveguide-coupled atoms induces correlations between simultaneously arriving photons through collectively enhanced nonlinear interactions. These correlated photons […]

Physicists ‘trick’ photons into behaving like electrons using a ‘synthetic’ magnetic field

Nanowerk  September 14, 2020 Researchers in the UK have shown that it is possible to create artificial magnetic fields for light by distorting honeycomb metasurfaces that are engineered to have structure on a scale much smaller than the wavelength of light. They embedded the metasurface in photonic cavity and showed that it is possible to tune the artificial magnetic field by changing only the width of the photonic cavity, thereby removing the need to modify the distortion in the metasurface. Using this mechanism it is possible to bend the trajectory of the polaritons using a tunable Lorentz-like force and also […]

Engineers manipulate color on the nanoscale, making it disappear

Nanowerk  August 13, 2020 An international team of researchers (USA – University of Pennsylvania, Industry, UCLA, Singapore) demonstrated that nanostructured, multilayer transition metal dichalcogenides (TMDCs) by themselves provide an ideal platform for excitation and control of excitonic modes, paving the way to exciton-photonics. Inherently strong TMDC exciton absorption resonances may be completely suppressed due to excitation of hybrid light-matter states and their interference. The work paves the way to the next generation of integrated exciton optoelectronic nano-devices and applications in light generation, computing, and sensing…read more. Open Access TECHNICAL ARTICLE

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 […]