Photonics - Page 11

Researchers from the DOE's Oak Ridge National Laboratory (ORNL) demonstrated that point defects in graphene are helpful in transferring atomic-scale data by integrating electrons with light. This could pave the way towards faster and smaller electronic devices. The team created the point defects by placing silicon atoms instead of carbon atoms. A two-atom silicon wire in graphene is capable of transforming light into an electronic signal and then converting the signal again into light.

The team says that the silicon atoms operate like atomic-scale antennae, thus improving graphene’s local surface plasmon response and forming an atomic-scale prototypical plasmonic device. The electron microscope used for the study is a component of the Shared Research Equipment User Facility of ORNL.

Researchers developed a new blue light emitting hybrid graphene oxide nanosheets. The team used surface functionalization to turn the cyan (491 nm) emitting sheets into 400 nm blue. The team fabricated the new material through the graphene oxide surface functionalization with aryl diazonium salts of 2-aminoanthracene.

The researchers say that these surface-functionalized graphene oxide hybrids has unique optical properties - and they may play an exciting role in opto-electronic devices.

The Electronic Materials Research Institute (eMRI) at Northeastern University will develop a graphene-based technology for use in low-cost infrared imaging applications for the US military. eMRI signed the research agreement with the United States Army Research Laboratory at Adelphi, Md. The Defense Advanced Research Projects Agency (DARPA) is also collaborating in this project.

According to researchers from eMRI, graphene can potentially revolutionize infrared cameras or night vision goggles used in a variety of military and civilian applications - enabling cheaper cameras which are low on size, weight and power. The research will focus on designing graphene-based bolometers, which measure heat generated by objects or people. The long-term goal is to license and mass-produce the technology for low-cost infrared cameras.

UK researchers say that introducing goldtitanium plasmonic nanostructures next to the electrical contacts of a graphene photodetector can significantly enhance its maximum voltage. The nanostructures convert incident light and into plasmonic oscillations and guide electromagnetic energy to the detector's pn junction.

The team performed several experiments to find the best geometries of the nanostructures. The best performance was given a comb structure (see photo above) - which caused the photovoltage to increase by up to a factor of 20.

Researchers from Singapore and the UK demonstrated a dramatic optical limiting effect in graphene using dispersed sub-oxidized graphene. While transparency in graphene is useful, having non-transparent (or light limiting) graphene also has its applications.

The optical-limiting effect achieved using suspensions of carbon nanotubes or carbon black occurs through a 'damage' mechanism involving the development of microbubbles or microplasmas at high light fluence, which increases light scattering and breaks the optical transparency.

Researchers from the University of Science and Technology of China developed a new robot that's made by layering a polyethylene film onto a glass layer and an adding a layer of graphene that is used to convert photothermal energy from infra red light. The robot can pick, move and drop objects. Such a design may be useful for surgery, for example. It can also inspire the design of transparent artificial muscles.

The team prepared the actuator by layering a polyethylene film onto a glass layer. On top of this, they added a graphene layer, which can absorb infrared light and convert this energy into heat with a high efficiency. The graphene - a sheet of carbon atoms one atom thick - also combines high transparency with strong mechanical performance. A strip of graphene on polyethylene that was 3mm by 12mm was then cut out and peeled off the glass, after which the strip curled up.

It's been known for a long time that Graphene generates current from light. Up until now everybody assumed it was due to the photovoltaic effect, but a new research by MIT researchers shows that this is not true. They found that light on graphene causes it to develop two regions with different electrical properties which creates a temperature difference.

This "hot-carrier response" is what generates the current - and it's very unusual - it's been observed before but only under very low temperature or when using intense high power laser. The reason for this unusual thermal response is that graphene is the strongest material known. In most materials, superheated electrons would transfer energy to the lattice around them. In the case of graphene, however, that’s exceedingly hard to do, since the material’s strength means it takes very high energy to vibrate its lattice of carbon nuclei — so very little of the electrons’ heat is transferred to that lattice.

The National Science Foundation (NSF) awarded a research grant to a Stevents Institute of Technology researcher to study the properties of graphene nanoribbons for use in infrared (IR) detection.

This funded research is to investigate the properties of actively controlled graphene nanoribbon arrays that researchers can "tune" for use in IR detectors covering an ultra-wide spectral range. In their awarded research, Dr. Yang and Dr. Strauf investigate nanoelectromechanical devices employing graphene nanoribbons to significantly improve IR detection schemes. Current IR detectors experience both limitations in their spectral range, for those that rely on the fixed IR absorption properties of detector materials, or their general sensitivities, in the case of tunable thermal detectors. The proposed concept offers the unique possibility of achieving high sensitivity across a wide spectral range with a single detection system.

Researchers from Berkeley built a microscale device that responds to light at terahertz frequencies. The device is an array made of graphene microribbons. By varying the width of the ribbons and the concentration of charge carriers in them, the scienstists were able to control the collective oscillations of electrons (plasmons) in the microribbons.

A new study finds that by combining graphene with metallic nanostructures, there was a 20-fold enhancement in the amount of light the graphene could harvest and convert into electrical power. The team (which included last year's Nobel Prize-winning scientists Andre Geim and Kostya Novoselov) says that these new graphene cell devices can be incredibly fast - tens or potentially hundreds of times faster than communication rates in the fastest Internet cables currently in use. The problem was the cell devices' low efficiency as graphene absorbs very little light (around 3%).

They now found that this problem can be solved by combining graphene with tiny metallic structures known as plasmonic nanostructures, which are specially arranged on top of graphene. The light-harvesting performance of graphene was boosted by 20 times without sacrificing any of its speed.