Photonics - Page 5

Researchers at Swinburne University of Technology, collaborating with Monash University, have developed an ultrathin, flat, lightweight graphene oxide optical lens with extraordinary flexibility, that enables potential applications in on-chip nanophotonics and improves the conversion process of solar cells. It might also open up new possibilities in areas like non-invasive 3D biomedical imaging, aerospace photonics, micromachines and more.

Recent developments in nano-optics and on-chip photonic systems have increased the demand for ultrathin flat lenses with 3D subwavelength focusing capability (the ability to see details of an object smaller than 200 nanometres). A number of ultrathin flat lens concepts have been developed, but their real-life application is limited due to their complex design, narrow operational bandwidth and time consuming manufacturing processes. This lens, however, has a 3D subwavelength capability that is 30 times more efficient, able to tightly focus broadband light from the visible to the near infrared, and offers a simple and low-cost manufacturing method.

A team of scientists from Columbia, Seoul National University (SNU), and Korea Research Institute of Standards and Science (KRISS) reported the creation of an on-chip visible light source using graphene as a filament. Creating light in small structures on the surface of a chip is crucial for developing fully integrated 'photonic' circuits that do with light what is now done with electric currents in semiconductor integrated circuits.

The scientists attached small strips of graphene to metal electrodes, suspended the strips above the substrate, and passed a current through the filaments to cause them to heat up. The team refers to this design as 'the world's thinnest light bulb', a type of 'broadband' light emitter that can be integrated into chips and may pave the way towards the realization of atomically thin, flexible, and transparent displays, and graphene-based on-chip optical communications.

Carbon Sciences announced its plans to develop graphene-based devices for cloud computing. Graphene-based fiber optics components, such as photodetectors, fiber lasers and optical switches, are expected to unclog the existing bottlenecks and enable ultrafast communication in data centers for Cloud computing.

The company states that it is shifting its focus to high value, large market opportunities to apply the knowledge gained from years of exploring methods to produce low cost graphene. Carbon Sciences estimates that contrary to many other applications that are years away from finding commercial success, cloud computing can soon create one of the most significant market opportunities in the world. By exploiting the excellent optical and electrical properties of graphene, the company plans to develop next generation fiber optics components that are ultrafast, low power and low cost.

A team of researchers from the École polytechnique fédérale de Lausanne (EPFL) in Switzerland claim to have captured the world's first image of light simultaneously showing both wave pattern and particle energy attributes.

The scientists used extremely short pulses of laser light directed at a miniscule nanowire made of silver and suspended on graphene film that acted as an electrical isolator (or metal-graphene dielectric). The nanowire acted as a small antenna that generated radiation patterns with the received laser excitation. The light traveled along the wire in two opposite directions and when these waves bounced back to the middle, they intersected with each other to form a new wave that appeared to be standing in place. This standing wave, radiating around the nanowire, then became the source of light used in the experiment.

A science and technology roadmap for graphene, related two-dimensional crystals, other 2d materials, and hybrid systems was put together in a joint effort by over 60 academics and industrialists. The roadmap covers the next 10 years and beyond, and its objective is to guide the research community and industry toward the development of products based on graphene and related materials.

The roadmap highlights three broad areas of activity. The first task is to identify new layered materials, assess their potential, and develop reliable, reproducible and safe means of producing them on an industrial scale. Identification of new device concepts enabled by 2d materials is also required, along with the development of component technologies. The ultimate goal is to integrate components and structures based on 2d materials into systems capable of providing new functionalities and application areas.

Scientists from ICFO, MIT, CNRS, CNISM and Graphenea collaborated to demonstrate how graphene can enable the electrical control of light at the nanometer level. Electrically controlled modulation of light emission is crucial in applications like sensors, displays and various optical communication system. It also opens the door to nanophotonics and plasmonics-based devices. 

The researchers managed to show that the energy flow from erbium into photons or plasmons can be controlled by applying a small electrical voltage. The plasmons in graphene are unique, as they are very strongly confined, with a plasmon wavelength that is much smaller than the wavelength of the emitted photons. As the Fermi energy of the graphene sheet was gradually increased, the erbium emitters went from exciting electrons in the graphene sheet, to emitting photons or plasmons. The experiments showed the graphene plasmons at near-infrared frequencies, which may be beneficial for communications applications. In addition, the strong concentration of optical energy offers new possibilities for data storage and manipulation through active plasmonic networks.

The field of plasmonics involves surface plasmons that are generated when photons hit a metal surface, and has been much talked about in regards to revolutionary photonic circuits. Researchers from ICFO (Barcelona), in a collaboration with CIC nanoGUNE (San Sebastian), and CNR/Scuola Normale Superiore (Pisa) and Columbia University (New York) claim to have solved one of the major problem in relation to plasmons - the rapid loss of energy that the plasmons experience, limiting the range over which they could travel.

The researchers found that a graphene-boron nitride system is an excellent host for confined light and suppression of plasmon losses (when graphene is encapsulated in boron nitride, electrons can move ballistically for long distances without scattering, even at room temperature).

Imec, the Belgian micro and nanoelectronics research center, together with Ghent University, demonstrated the world's first integrated graphene optical electro-absorption modulator (EAM) capable of 10Gb/s modulation speed in a recent IEEE International Electron Devices Meeting (IEDM 2014).

The modulator combines low insertion loss, low drive voltage, high thermal stability, broadband operation and compact footprint. Such integrated can be highly beneficial for future chip-level optical interconnects.

Nokia has recently issued what could be a truly revolutional patent: a self-charging graphene-based photon battery, capable of being printed on flexible substrates.

The patent describes a battery that can regenerate itself immediately after discharge through continuous chemical reactions, without an external energy input. The result is an energy autonomous device. The battery uses humid air for the purpose of recharging and be made highly transparent.

Researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) conducted a study on the dynamics of graphene electrons in a magnetic field, which reportedly yielded fascinating results.

The HZDR researchers exposed graphene to an extremely strong (four-tesla) magnetic field, and as a result the electrons occupied only certain energy states. These energy levels were examined with free-electron laser light pulses which excites the electrons into a certain Landau level. The surprising result of this test was that the particular energy level in which the electrons were arranged via the laser gradually emptied.

A model of the electron redistribution that HZDR researchers discovered

It has been established that energy states of graphene in a magnetic field - known as Landau levels - behave differently than those of semiconductors. Yet, the scientists claim, not many researchers tested the dynamics of electrons in such a magnetic field system.