A team of engineers has developed a new acousto-optic device that can shape and steer beams of light at speeds never before achieved. The new technology will enable better optical devices to be made, such as holographs that can move rapidly in real time. The research led by Bruce Drinkwater, Professor of Ultrasonics at the University of Bristol and Dr Mike MacDonald at the University of Dundee is published in the journal, ("Tunable beam shaping with a phased array acousto-optic modulator"). 
This image shows a new optical beam-forming device making 'twisted light.' (Image: Universities of Bristol and Dundee) The array consists of 64 tiny piezo-electric elements which act as high frequency loudspeakers. The complex sound field generated deflects and sculpts any light passing through the new device. As the sound field changes, so does the shape of the light beam. Professor Drinkwater from the Department of Mechanical Engineering said: "This reconfigurability can happen extremely fast, limited only by the speed of the sound waves. The key advantage of this method is that it potentially offers very high refresh rates - millions of refreshes per second is now possible. This means that in the future laser beam-based devices will be able to be reconfigured much faster than is currently possible. Previously, the fastest achieved is a few thousand refreshes per second." The advancement will enable reconfigurable lenses that can automatically compensate for aberrations allowing for improved microscopy and a new generation of optical tweezers that will make them more rapidly reconfigurable and so allow better shaped traps to be produced. Dr Mike MacDonald, Head of the Biophotonics research group at the University of Dundee, explained: "What we have shown can be thought of as a form of optical holography where the hologram can be made in real time using sound. Previous attempts to do this have not had the level of sophistication that we have achieved in the control of our acoustic fields, which has given us much greater flexibility in the control we have over light with these devices. "The device can potentially be addressed much more quickly than existing holographic devices, such as spatial light modulators, and will also allow for much higher laser powers to be used. This opens up applications such as beam shaping in laser processing of materials, or even fast and high power control of light beams for free space optical communications using orbital angular momentum to increase signal bandwidth, as shown recently by a demonstration in Vienna." Professor Drinkwater added: "The number of applications of this new technology is vast. Optical devices are everywhere and are used for displays, communications as well as scientific instruments." The capabilities of laser beam shaping and steering are crucial for many optical applications, such as optical manipulation and aberration correction in microscopy. Depending on specific requirements of each application, these capabilities are currently achieved using different methods which are based on establishing a certain level of control over the phase of the laser beam. Deformable mirrors are used for aberration corrections in astronomy and spatial light modulators (SLMs) are the common choice in a wide range of applications such as holography, optical tweezers and microscopy.
This image shows a new optical beam-forming device making 'twisted light.' (Image: Universities of Bristol and Dundee) The array consists of 64 tiny piezo-electric elements which act as high frequency loudspeakers. The complex sound field generated deflects and sculpts any light passing through the new device. As the sound field changes, so does the shape of the light beam. Professor Drinkwater from the Department of Mechanical Engineering said: "This reconfigurability can happen extremely fast, limited only by the speed of the sound waves. The key advantage of this method is that it potentially offers very high refresh rates - millions of refreshes per second is now possible. This means that in the future laser beam-based devices will be able to be reconfigured much faster than is currently possible. Previously, the fastest achieved is a few thousand refreshes per second." The advancement will enable reconfigurable lenses that can automatically compensate for aberrations allowing for improved microscopy and a new generation of optical tweezers that will make them more rapidly reconfigurable and so allow better shaped traps to be produced. Dr Mike MacDonald, Head of the Biophotonics research group at the University of Dundee, explained: "What we have shown can be thought of as a form of optical holography where the hologram can be made in real time using sound. Previous attempts to do this have not had the level of sophistication that we have achieved in the control of our acoustic fields, which has given us much greater flexibility in the control we have over light with these devices. "The device can potentially be addressed much more quickly than existing holographic devices, such as spatial light modulators, and will also allow for much higher laser powers to be used. This opens up applications such as beam shaping in laser processing of materials, or even fast and high power control of light beams for free space optical communications using orbital angular momentum to increase signal bandwidth, as shown recently by a demonstration in Vienna." Professor Drinkwater added: "The number of applications of this new technology is vast. Optical devices are everywhere and are used for displays, communications as well as scientific instruments." The capabilities of laser beam shaping and steering are crucial for many optical applications, such as optical manipulation and aberration correction in microscopy. Depending on specific requirements of each application, these capabilities are currently achieved using different methods which are based on establishing a certain level of control over the phase of the laser beam. Deformable mirrors are used for aberration corrections in astronomy and spatial light modulators (SLMs) are the common choice in a wide range of applications such as holography, optical tweezers and microscopy.
This shows the first experimental observation of 5/2 FQHE state. (© Science China Press) The 5/2 filling factor state is special for being an even denominator state, since most of the previously observed fractional quantum Hall states have odd denominator fractions. The observation of the 5/2 state demands new theoretical concepts. This even denominator fractional quantum Hall state can be viewed as a new testing ground to study complicated many-body physics involving simple electrons. Their paper covers the progress of the 5/2 state in terms of energy gap, spin polarization study, fractional charge and statistics. The relationship between the energy gap and other experimental parameters, such as electron density, mobility, sample quality, are outlined. The confusing results of spin polarization and the interference experiments are also reviewed. The Peking University scientists acknowledge in the paper that the "5/2 state needs extra efforts to determine its ground state wave function." The paper's co-authors likewise survey recent progress in researching FQHE in monolayer graphene. Graphene has gained increasing scientific attention due to its peculiar band structure, corresponding two-dimensional massless Dirac-like excitations and great application potential. The quantum Hall effect in graphene has even been found at room temperature, which makes QHE-based applications more attractive and likely to become a focus of research in the future. The FQHE has been observed in graphene since 2009. Typically this effect has been studied in semiconductors and graphene as a new platform for two-dimensional electrons. FQHE in graphene provides an interesting platform for experiments in many-body physics.
(Image: Zhen Gu) In this study ("Furin-Mediated Sequential Delivery of Anticancer Cytokine and Small-Molecule Drug Shuttled by Graphene"), the researchers attached two drugs – TRAIL and doxorubicin (Dox) – onto graphene strips. Graphene is a two-dimensional sheet of carbon that is only one atom thick. Because TRAIL is most effective when delivered to the external membrane of a cancer cell, while Dox is most effective when delivered to the nucleus, the researchers wanted to deliver the drugs sequentially, with each drug hitting a cancer cell where it will do the most damage. The Dox is physically bound to the graphene due to similarities in the molecular structure of the drug and the graphene. The TRAIL is bound to the surface of the graphene by a chain of amino acids called peptides. “These drug-rich graphene strips are introduced into the bloodstream in solution, and then travel through the bloodstream like nanoscale flying carpets,” explains Dr. Zhen Gu, senior author of a paper describing the work and an assistant professor in the joint biomedical engineering program at NC State and UNC-Chapel Hill. Once in the bloodstream, these flying carpets take advantage of the fact that cancer tumors cause nearby blood vessels to leak by using those leaks to penetrate into the tumor. When the flying carpet comes into contact with a cancer cell, receptors on the surface of the cell latch onto the TRAIL. Meanwhile, enzymes that are common on the surface of cancer cells sever the peptides linking the TRAIL and the graphene. This allows the cell to absorb the Dox-laden graphene and leaves the TRAIL on the surface, where it begins a process to trigger cell death. After the flying carpet is “swallowed” by the cell, the acidic environment inside the cell promotes the separation of the Dox from the graphene – freeing it to attack the nucleus. “We’ve demonstrated that TRAIL itself can be used to attach a drug delivery system to a cancer cell, without using intervening material – which is something we didn’t know,” Gu says. “And because graphene has a large surface area, this technique enhances our ability to apply TRAIL to its target on cancer cell membranes.” The researchers tested the flying carpet drug delivery technique in preclinical trials against human lung cancer tumors (cell line A549) in laboratory mice. The technique was significantly more effective than Dox or TRAIL by themselves, or to a combination of Dox and TRAIL in which the peptide link between the graphene and the TRAIL couldn’t be severed. “We’re now trying to secure funding to support additional preclinical studies in order to determine how best to proceed with this new technique,” Gu says.