Lasers - Page 4

Researchers at the Rice University have devised a process in which a computer-controlled laser burns through a polymer to create flexible, patterned sheets of multilayer graphene that may be suitable for electronics or energy storage. The process works in air at room temperature, cancelling the need for hot furnaces and controlled environments.

The product of this process is not a 2D piece of graphene but a porous foam of interconnected flakes about 20 microns thick. The laser doesn't cut all the way through the base material, so the foam remains attached to a flexible plastic base.

Researchers from the Korea Electrotechnology Research Institue (KERI) managed to create an innovative process of 3D printing graphene nanostructures.

The scientists announced the development of a nanoscale 3D printing approach that exploits a liquid meniscus of ink to create 3D reduced graphene oxide (rGO) nanowires, different than typical methods that use filaments or powders as printing materials.

Scientists at the University of Kansas managed to fabricate an innovative substance made of an atomic sheet of graphene interlocked with a sheet tungsten disulfide that could be used for solar cells and flexible electronics.

The material was formed using "layer to layer assembly" as a versatile bottom-up nanofabrication technique. The scientists then examined the motion of electrons between the layers through ultrafast laser spectroscopy, and found that nearly 100% of the electrons that absorbed energy from the laser pulse moved from the tungsten layer to the graphene within one picosecond, proving that the new material combines the properties of each component layer.

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.

In December 2011 the EU launched a graphene project called NanoMaster with an aim to develop up-scale processing methods for production of graphene and expanded graphite reinforced thermoplastic masterbatches and compounds. Today the project partners announced that the project is entering its final phase, and is reporting exciting results.

Recently, the project team focused on optimizing and up-scaling the processes for graphene and expanded graphite production, and their subsequent compounding with a range of thermoplastics. They have now achieved a graphene production capacity increase from 50 grams to 2.5 Kg.

Researchers from the University of Manchester (with help from an international team of scientists) discovered that if you stack two graphene sheets on on top of the other (bi-layer graphene) in a certain way, it actually cools down when hit with laser light.

The two graphene sheets are aligned so one sheet is rotated by 11.3 degrees. With a specific laser energy, instead of heating up like any "normal" material - it cools down. The researchers explain that the photons of the laser absorb the vibration energy of the atoms - instead of the other way around.

Researchers from Rice and Osaka Universities discovered a simple method to measure contaminants on graphene sheets using terahertz spectroscopy.

The researchers placed the graphene on a layer of Indium Phosphide, and then used a laser pulse on the graphene. This causes the materials to emit terahertz waves, which can then be used to map contaminants (which change graphene's electrical properties) on the graphene sheet.

Researchers at Melbourne's Swinburne University developed a high-quality continuous graphene oxide thin film that has a record-breaking optical nonlinearity. The film may be suitable for high performance integrated photonic devices - useful for communication, biomedcine and photonic computing.

To create this new film, the researchers first spin-coated a graphene-oxide solution on a glass substrate. They then used a laser to create microstructures on the graphene oxide film to tune the nonlinearity of the material. Now they have a platform to fabricate optical components with desired nonlinearity - and all on the same graphene sheet without the need to integrate different components.

Researchers from the National University of Singapore created the world's first nanosized heat engine, made from nanometre-thick fluorinated graphene. Such a tiny engine may be useful in nanorobotics and nanomachines. It can also be used as a valve for microfluids.

The new nano-engine is made of graphene and weakly chemisorbed ClF₃ molecules. The CIF₃ molecules are used as actuators. The engine uses a laser light beam as the ignition plug - when the CIF₃ molecules are exposed to the laser (532 nm wavelength) they sublimate - which expand the volume at the interface between the graphene and the substrate it is grown on. This generates a high pressure (around 23 MPa) and creates a "dome-like blister". The expansion (and later contraction when the laser is turned off) is equivalent to the motion of a piston in an internal combustion engine. The blister size can be controlled by changing the laser power.

The EU launched a new project called Graphenics that aims to develop an ultra-compact graphene-based mid-infrared broadband light source. The project include researchers from Belgium, Austria, Poland and Canada. The hope to achieve a highly compact and portable device, that will pave the way to mid-infrared broadband light sources in applications such as medical diagnostics and optical safety testing of water.

The researchers say that the main issue stopping the widespread adoption of broadband mid-infrared light source is the source compactness and portability. The researchers hope to develop a chip in which both the chip and the pump laser exciting the chip are made extremely compact.