Phys.org June 28, 2018 Most current cloaking devices can fully conceal the object of interest only when the object is illuminated with just one color of light. Researchers in Canada propose a new conceptual approach enabling the realization of full-field broadband invisibility. This involves a customized and reversible redistribution of the illumination frequency content, allowing the wave to propagate through the object of interest while preventing any interaction between the wave and the object. They demonstrated the concealment of a broadband optical filter from detection with a phase-coherent light pulse of 500 GHz bandwidth, showing full restoration of the complex […]
Tag Archives: Photonics
New approach to generating ultrashort laser pulses
Nanowerk June 8, 2018 An international team of researchers (USA – MIT, The Ohio State University, Germany) used an optical parametric amplifier to produce pulses which cover different spectral ranges and whose amplitudes and phases can be fixed relative to one another. The amplifier has a very short time delay between the two pulses so that they combine into a wide-bandwidth pulse with no need for noise control. The pulse could be made even shorter than the period of the wave because constructive interference occurs at its center, while destructive interference ‘trims’ the pulse at its edges. When the pulses […]
Graphene sets a new record on squeezing light to one atom
Science Daily April 20, 2018 An international team of researchers (Spain, France, Portugal, USA – MIT) has shown that a graphene-insulator-metal heterostructure can overcome energy loss and demonstrate plasmon confinement down to the ultimate limit of the length scale of one atom. This is achieved through far-field excitation of plasmon modes squeezed into an atomically thin hexagonal boron nitride dielectric spacer between graphene and metal rods. A theoretical model that takes into account the nonlocal optical response of both graphene and metal is used to describe the results. These ultraconfined plasmonic modes, addressed with far-field light excitation, enable a route […]
For the first time, researchers place an electron in a dual state – neither freed nor bound
Phys.org April 16, 2018 An international team of researchers (Switzerland, Germany, Spain) controlled the shape of the laser pulse to keep an electron both free and bound to its nucleus and regulate the electronic structure of the atom. They made these unusual states amplify laser light and identified a no-go area, nicknamed “Death Valley,” where they lost all their power over the electron. These results shatter the usual concepts related to the ionisation of matter. The discovery gives the option of creating new atoms dressed by the field of the laser, with new electron energy levels. This will play a […]
New device modulates light and amplifies tiny signals
Phys.org April 9, 2018 Researchers at NIST have created a plasmomechanical oscillator (PMO) that tightly couples plasmons to the mechanical vibrations of the much larger device in which it is embedded. The device consists of a gold nanoparticle, about 100 nanometers in diameter, embedded in a tiny cantilever made of silicon nitride. An air gap lies sandwiched between these components and an underlying gold plate; the width of the gap is controlled by an electrostatic actuator and bends toward the plate when a voltage is applied. The nanoparticle acts as a single plasmonic structure that has a natural frequency that […]
Generating energy from fluctuations of light
Phys.org March 27, 2018 Researchers in Sweden have developed a method and a material that generates an electrical impulse when the light fluctuates from sunshine to shade and vice versa. They created a tiny optical generator by combining the small antennas consisting gold nanodiscs placed on a substrate and coated with a polymeric film to create the pyroelectric properties. The antennas generate heat that is then converted to electricity with the aid of the polymer. The degree of polarisation of the polymer affects the magnitude of the generated power, while the thickness not to have any effect at all. Applications […]
New hole-punched crystal clears a path for quantum light
Science Daily February 15, 2018 Researchers at the University of Maryland created a photonic chip that both generates single photons and steers them around. In the new chip, they etched out thousands of triangular holes in an array that resembled a bee’s honeycomb. Along the center of the device they shifted the spacing of the holes, which opens a different kind of travel lane for the light. The team tested the capabilities of the chip by first changing a quantum emitter from its lowest energy state to one of its two higher energy states. When they used photons from the […]
Physicists create new form of light
MIT News February 15, 2018 A team of researchers in the US (MIT, Harvard University, Princeton University, NITS, University of Chicago) has observed groups of three photons interacting and, in effect, sticking together to form a completely new kind of photonic matter. In controlled experiments, the researchers found that when they shone a very weak laser beam through a dense cloud of ultracold rubidium atoms, rather than exiting the cloud as single, randomly spaced photons, the photons bound together in pairs or triplets, suggesting some kind of interaction — in this case, attraction — taking place among them. According to […]
New exotic phenomena seen in photonic crystals
MIT News January 11, 2018 A team of researchers in the US (MIT, Yale University) used a method that made these open systems accessible and found two specific kinds of effects that are distinctive topological signatures of non-Hermitian systems. One of these is a kind of band feature they refer to as a bulk Fermi arc, and the other is an unusual kind of changing polarization emitted by the photonic crystal used for the study. Most of the potential real-world applications for photonic crystals involve open systems, so the new observations made by this team could open new areas of […]