#Graphene flakes as an ultra-fast stopwatch Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), working with colleagues from the USA and Germany, have developed a new optical detector from graphene
which reacts very rapidly to incident light of all different wavelengths and even works at room temperature.
It is the first time that a single detector has been able to monitor the spectral range from visible light to infrared radiation and right through to terahertz radiation.
The HZDR scientists are already using the new graphene detector for the exact synchronization of laser systems.
A tiny flake of graphene on silicon carbide and a futuristic-looking antenna and there it is the new graphene detector.
this comparatively simple and inexpensive construct can cover the enormous spectral range from visible light all the way to terahertz radiation."
The detector can register incident light in just 40 picoseconds these are billionths of a second.
"Semiconductor substrates used in the past have absorbed always some wavelengths but silicon carbide remains passive in the spectral range,
therefore been able to increase the spectral range by a factor of 90 in comparison with the previous model, making the shortest detectable wavelength 1000 times smaller than the longest.
By way of comparison, red light, which has the longest wavelength visible to the human eye,
is only twice as long as violet light which has the shortest wavelength on the visible spectrum. This optical universal detector is already being used at the HZDR for the exact synchronization of the two free-electron lasers at the ELBE Center for High-power Radiation Sources with other lasers.
This alignment is particularly important for"pump probe"experiments, as they are called, where researcher take one laser for the excitation of a material("pump)
"and then use a second laser with a different wavelength for the measurement("probe")."The laser pulses must be synchronized exactly for such experiments.
So the scientists are using the graphene detector like a stopwatch. It tells them when the laser pulses reach their goal,
and the large bandwidth helps to prevent a change of detector from being a potential source of error.
Another advantage is that all the measurements can take place at room temperature, obviating the need for the expensive and time-consuming nitrogen or helium cooling processes with other detectors c
#Engineers reveal record-setting flexible phototransistor Inspired by mammals'eyes, University of Wisconsin-Madison electrical engineers have created the fastest,
most responsive flexible silicon phototransistor ever made. The innovative phototransistor could improve the performance of myriad products-ranging from digital cameras,
then convert that light into an electrical charge proportional to its intensity and wavelength. In the case of our eyes, the electrical impulses transmit the image to the brain.
"In this structure-unlike other photodetectors-light absorption in an ultrathin silicon layer can be much more efficient
and improve light absorption without the need for an external amplifier.""There's a built-in capability to sense weak light,
"Ma says. Ultimately, the new phototransistors open the door of possibility, he says.""This demonstration shows great potential in high-performance and flexible photodetection systems,"says Ma,
then convert that light into an electrical charge proportional to its intensity and wavelength. In the case of our eyes, the electrical impulses transmit the image to the brain.
"In this structure-unlike other photodetectors-light absorption in an ultrathin silicon layer can be much more efficient
and improve light absorption without the need for an external amplifier.""There's a built-in capability to sense weak light,
"Ma says. Ultimately, the new phototransistors open the door of possibility, he says.""This demonstration shows great potential in high-performance and flexible photodetection systems,"says Ma,
and photons, said Vladimir M. Shalaev, co-director of a new Purdue Quantum Center, scientific director of nanophotonics at the Birck Nanotechnology Center and a distinguished professor of electrical and computer engineering."
increasing the velocity of particle transport by 100 times by applying an alternating current electric field in conjunction with heating the plasmonic nanoantenna using a laser to induce a force far stronger than otherwise possible."
"The new hybrid nanotweezer combines a near-infrared laser light and an electric field, inducing an"electrothermoplasmonic flow.""
""Then, once we turn off the electric field the laser holds the particles in place, so it can operate in two modes.
The laser traps the particles, making it possible to precisely position them. The technique was demonstrated with polystyrene particles i
and light in photonic crystals May 9th, 2015penn and UC Merced researchers match physical and virtual atomic friction experiments May 8th, 201 0
"The unique three-dimensionality interconnected nanoporous nature of our coatings significantly suppresses Fresnel light reflections from glass surfaces, providing enhanced transmission over a wide range of wavelengths and angles,
The Fresnel effect describes the amount of light that is reflected versus the amount transmitted. Where solar panels are concerned,
the suppression of reflected light translates into a 3-6 percent relative increase in light-to-electricity conversion efficiency and power output of the cells.
the coating is highly effective at blocking ultraviolet light. Other potential applications include goggles, periscopes, optical instruments, photodetectors and sensors.
In addition, the superhydrophobic property can be effective at preventing ice and snow buildup on optical elements and can impede biofouling in marine applications.
Broadband/Omnidirectional Light Harvesting and Self-Cleaning Characteristics,"were Andrew Lupini, Gerald Jellison, Pooran Joshi, Ilia Ivanov, Tao Liu, Peng Wang, Rajesh
That means little light is lost and the quantum efficiency is virtually very high. In addition, it has been reported in the very recently published article that the composite shows high long-term stability over 25 hours
It is capable of delivering extremely localised heating from a near-infrared laser aimed at the gold nanorods
When exposed to green light, these centres emit a red fluorescent light, useful for sub-cellular imaging applications.
Unlike ordinary fluorescent material, these centres can also be turned into hypersensitive nanoprobes to detect temperature and magnetic field, via optical manipulation and detection.
the authors make it possible to convert the incoming laser light into extremely localised heat. These gold nanoparticles can
using a laser as the energy source. The novelty of this study is that it shows that it is possible to use diamond nanocrystals as hypersensitive temperature sensors with a high spatial resolution-ranging from 10 to 100 nanometers-to monitor the amount of heat delivered to cancer cells s
"Hybrid approaches such as ours bring together multiple capabilities, in this case, spectroscopy and high-resolution microscopy.""Looking inside, the hybrid microscope consists of a photonic module that is incorporated into a mode-synthesizing atomic force microscope.
The modular aspect of the system makes it possible to accommodate various radiation sources such as tunable lasers and non-coherent monochromatic or polychromatic sources s
near-field optical microscopy and ultra-fast spectroscopy. Computer-assisted technology developed especially for this purpose combines the advantages of both methods
microscopy and ultra-fast spectroscopy. It enables unaltered optical measurements of extremely small, dynamic changes in biological, chemical or physical processes.
which laser light is irradiated on a ultra-thin metal point. This creates highly bundled light-a hundred times smaller than the wavelength of light,
which otherwise represents the limit of"normal"optics with lenses and mirrors.""In principle, we can use the entire wavelength spectrum of near-field microscopy,
from ultraviolet to the terahertz range,"says Dr. Susanne Kehr from the TU Dresden.""The focused light delivers energy to the sample,
creating a special interaction between the point and the sample in what is known as the near-field.
By observing the back-scattered portion of the laser light, one can achieve a spatial resolution in the order of the near-field magnitude, that is, in the nanometer range."
Using ultra-fast spectroscopy is the crucial tool, on the other hand, enabling scientists to study dynamic processes on short timescales and with extreme sensitivity.
The principle in such pump-probe experiments that function, for example, with light, pressure or electric field pulses is as follows:
which--in addition to the outstanding resolution of near-field optical microscopy that is at least three orders of magnitude better than the resolution of common ultra-fast spectroscopy--we can now also measure dynamic changes in the sample with high sensitivity,
Universal in every respect"With our nanoscope's considerable wavelength coverage, dynamic processes can be studied with the best suited wavelengths for the specific process under study.
Our colleagues at the Freie Universität Berlin have, for example, the ambitious dream of tracking structural changes during the photocycle of an individual membrane protein at specific wavelengthes in the infrared spectrum,
The probe pulse wavelengths can, in principle, reach from the low terahertz range to the ultraviolet range.
The sample can be stimulated with laser, pressure, electric field or magnetic field pulses. The principle was tested at the HZDR on a typical laboratory laser as well as on the free-electron laser FELBE.
First tests on the new terahertz source TELBE which provides extremely short electric and magnetic field pulses for excitation,
and then fixed them in place using a procedure called light-triggered in-situ vinyl polymerization, which essentially uses light to congeal a substance into a hydrogel.
The nanosheets ended up stuck within the polymer, aligned in a single plane. Due to electrostatic forces, the sheets create electrostatic resistance in one direction but not in the other.
when they are exposed to near-infrared light. In addition, a gene therapy is administered that lowers the cellular defense against reactive oxygen species. Both the phthalocyanine
this approach allows the near-infrared light to penetrate much deeper into abdominal tissues, and dramatically increases the effectiveness of the procedure in killing cancer cells.
"and fluoresce when exposed to near-infrared light. This provides a literal road map for surgeons to follow,
#New optical chip lights up the race for quantum computer The microprocessor inside a computer is a single multipurpose chip that has revolutionised people's life,
Now, researchers from the University of Bristol in the UK and Nippon Telegraph and Telephone (NTT) in Japan, have pulled off the same feat for light in the quantum world by developing an optical chip that can process photons in an infinite number
and control quantum states of light and matter. A major barrier in testing new theories for quantum science and quantum computing is the time
because the world's leading quantum photonics group teamed up with Nippon Telegraph and Telephone (NTT), the world's leading telecommunications company.
Professor Jeremy O'brien, Director of the Centre for Quantum Photonics at Bristol University, explained:""Over the last decade, we have established an ecosystem for photonic quantum technologies,
Berkeley Lab scientist invents technique to combine spectroscopy with super-resolution microscopy, enabling new ways to examine cell structures
Berkeley Lab scientist invents technique to combine spectroscopy with super-resolution microscopy, enabling new ways to examine cell structures
The research was reported in the journal Nature Methods in a paper titled,"Ultrahigh-throughput single-molecule spectroscopy and spectrally resolved super-resolution microscopy"
Next they dyed the sample with 14 different dyes in a narrow emission window and excited and photoswitched the molecules with one laser.
while still allowing light and electrons to pass through. The new complete solar fuel generation system developed by Lewis
and professors Randy Headrick and Madalina Furis, deployed this table-top scanning laser microscope. Their latest finding is reported in the journal Nature Communications--and may
and convert the light into electric current using excited states in the material called"excitons.""Roughly speaking, an exciton is displaced a electron bound together with the hole it left behind.
the UVM team--with support from the National Science Foundation--built a scanning laser microscope,
The instrument combines a specialized form of linearly polarized light and photoluminescence to optically probe the molecular structure of the phthalocyanine crystals."
At the Frontiers in Optics conference researchers will describe a custom-built ultrafast laser that could help image everything from semiconductor chips to cells in real time Using ultrafast beams of extreme ultraviolet light streaming at a 100,000 times a second, researchers
Not only did they make the highest resolution images ever achieved with this method at a given wavelength,
The researchers'wanted to improve on a lensless imaging technique called coherent diffraction imaging, which has been around since the 1980s.
scientists fire an X-ray or extreme ultraviolet laser at a target. The light scatters off, and some of those photons interfere with one another
creating a diffraction pattern. By analyzing that pattern, a computer then reconstructs the path those photons must have taken,
Over the last ten years, researchers have developed smaller, cheaper machines that pump out coherent, laser-like beams in the laboratory setting.
Zürch and a team of researchers from Jena University used a special, custom-built ultrafast laser that fires extreme ultraviolet photons a hundred times faster than conventional table-top machines.
With more photons, at a wavelength of 33 nanometers, the researchers were able to make an image with a resolution of 26 nanometers--almost the theoretical limit."
"Nobody has achieved such a high resolution with respect to the wavelength in the extreme ultraviolet before, "Zürch said.
The ultrafast laser also overcame another drawback of conventional table-top light sources: long exposure times.
Thanks to the new high-speed light source, Zürch and his colleagues have reduced the exposure time to only about a second--fast enough for real-time imaging.
The new material, produced by grain boundary lithography, solves that problem, he said. In addition to Ren, other researchers on the project included Chuan Fei Guo and Ching-Wu"Paul"Chu, both from UH;
The grain boundary lithography involved a bilayer lift off metallization process, which included an indium oxide mask layer and a silicon oxide sacrificial layer and offers good control over the dimensions of the mesh structure.
the less efficient they become at converting the photons in light into useful electricity. The Stanford solution is based on a thin,
in the form of infrared light, into space. Their experiments showed that the overlay allowed visible light to pass through to the solar cells,
but that it also cooled the underlying absorber by as much as 55 degrees Fahrenheit. For a typical crystalline silicon solar cell with an efficiency of 20 percent, 55 F of cooling would improve absolute cell efficiency by over 1 percent,
perhaps using nanoprint lithography, which is a common technique for producing nanometer scale patterns.""That's not necessarily the only way,"said Raman, a co-first-author of the paper."
"That's because the perception of color requires objects to reflect visible light, so any overlay would need to be tuned transparent,
"Our photonic crystal thermal overlay optimizes use of the thermal portions of the electromagnetic spectrum without affecting visible light,
#Pioneering research develops new way to capture light--for the computers of tomorrow Pioneering research by an international team of scientists,
data transfer by means of light-have long since become part of our everyday life, data on a computer are processed still
The team of scientists from Germany and England have made a key breakthrough by capturing light on an integrated chip,
The research is published in leading scientific journal, Nature Photonics. Professor David Wright from the University of Exeter's Engineering department said:"
this tool should provide fast and reliable characterization of the different mechanisms cellular proteins use to bind to DNA strands--information that could shed new light on the atomic-scale interactions within our cells
"Generally, most existing techniques to look at single-molecule movements--such as optical tweezers--have a resolution, at best,
The work demonstrates the potential of low energy electron holography as a non-destructive, single-particle imaging technique for structural biology.
"We've shown that by means of low energy holography, it is possible to image individual tobacco mosaic virions deposited on ultraclean freestanding graphene,
Low energy electron holography is a technique of using an electron wave to form holograms. Similar to light optical holography
albeit with a much smaller wavelength, the complete information of the scattered wave, such as phase and amplitude, is recorded
thus enabling an unambiguous reconstruction of the object's structure.""The low energy electron holography has two major advantages over conventional microscopy.
First, the technique doesn't employ any lenses, so the resolution won't be limited by lens aberration.
in low energy electron holography, the employed electron doses can be much higher--even after exposing fragile molecules like DNA or proteins to a electron dose more than five orders of magnitude higher
Sufficient electron dose in low energy electron holography makes imaging individual biomolecules at a nanometer resolution possible.
To obtain the high-resolution hologram, an atomically sharp, tungsten tip acts as a source of a divergent beam of highly coherent electrons.
the researchers recorded the sample's high-resolution hologram, a pattern resulting from the interference of the two beams."
"Since low energy electron holography is a method very sensitive to mechanical disturbance, the current nanometer resolution could be improved to angstrom (one ten billionth of a meter)
"In this light, Lu's invention represents a major advancement for the mobile health industry.""After producing the cut-and-pasted patches,
we have made two major advances--the ability to precisely control the brightness of light-emitting particles called quantum dots,
because the amount of light emitted from a single dye is unstable and often unpredictable.
These attributes obscure correlations between measured light intensity and concentrations of molecules,"stated Sung Jun Lim, a postdoctoral fellow and first author of the paper"
and improve color tuning in light-emitting devices. In addition, BE-QDS maintain their equal brightness over time
thus requiring even faster optical detectors that can be integrated into photonic circuits. In the recent work published today in Nature Nanotechnology,
By using ultra-fast laser pulses the researchers have shown a record-high photo-response speed for a heterostructure made of two-dimensional materials.
An important advantage of these devices based on graphene and other two-dimensional materials is that they can be integrated monolithically with silicon photonics enabling a new class of photonic integrated circuits.
the next step is to develop prototype photonic circuitry and explore ways to improve large-scale production of these devices.
"ICFO researcher Mathieu Massicotte and first author of this study states that"Everyone knew graphene could make ultrafast photodetectors,
we can obtain a photodetector that is not only ultrafast but also highly efficient.""The results obtained from this study have shown that the stacking of semiconducting 2d materials with graphene in heterostructures could lead to new, fast and efficient optoelectronic applications,
Chance effect of lab's fluorescent lights leads to discovery In contrast to using advanced nanofabrication facilities based on chemical processing of materials,
"It's one of those rare moments in experimental science where a seemingly random event--turning on the room lights--generated unexpected effects with potentially important impacts in science and technology."
"There was a slow drift in our measurements that we traced to a particular type of fluorescent lights in our lab. At first we were glad to be rid of it,
and then it struck us--our room lights were doing something that people work very hard to do in these materials."
the contractor that renovated the lab space for more information about the lights.""I've never had a client
when exposed to ultraviolet light, and their room lights happened to emit at just the right wavelength.
The electric field from the polarized strontium titanate was leaking into the topological insulator layer, changing its electronic properties.
Awschalom and his colleagues found that by intentionally focusing beams of light on their samples,
they could draw electronic structures that persisted long after the light was removed.""It's like having a sort of quantum etch-a-sketch in our lab,
They also found that bright red light counteracted the effect of the ultraviolet light, allowing them to both write and erase."
With many photonics and electronics applications, there has been considerable effort in creating artificial materials with optical and dielectric properties similar to air
In this case, the light has a much lower frequency than ordinary light and in reality is microwaves."
#Researchers transform slow emitters into fast light sources Researchers from Brown University, in collaboration with colleagues from Harvard, have developed a new way to control light from phosphorescent emitters at very high speeds.
The technique provides a new approach to modulation that could be useful in all kinds of silicon-based nanoscale devices,
a process that often involves flipping the light on and off to encode information. Because of their slow lifetimes, phosphors have traditionally been a nonstarter for applications that require high-speed modulation.
"Instead of changing how much light is coming out, which can only be done slowly in phosphor emitters,
we came up with a system that changes another quality of that light, namely the color or spectrum of light emission,
Prototype on-chip networks have used semiconductor lasers as light emitters. They can modulate very quickly,
What's more, semiconductor lasers are not particularly efficient. They produce a lot of heat along with light
which is a problem on a silicon chip. Erbium and other phosphors, on the other hand, can be deposited directly on silicon, making fabrication easier.
In this initial experiment, the researchers used a laser to zap the VO2 and cause it to change phase.
A faster means of changing the VO2 phase--perhaps using electricity instead of a laser--could make the system much faster still.
and industrial researchers working on optoelectronics and nanophotonics, "the researchers write e
#Monitoring critical blood levels in real time in the ICU: EPFL has developed a miniaturized microfluidic device that will allow medical staff to monitor in real time levels of glucose,
Among other advantages of the cells, mention can be made of simple production method, appropriate final price and high transparency for the light.
while testing a laser-based measurement technique that they recently developed to look for what is called multipolar order.
when you look at an object illuminated by a single frequency of light, all of the light that you see reflected from the object is at that frequency.
When you shine a red laser pointer at a wall, for example, your eye detects red light. However, for all materials, there is a tiny amount of light bouncing off at integer multiples of the incoming frequency.
So with the red laser pointer, there will also be some blue light bouncing off of the wall.
You just do not see it because it is such a small percentage of the total light.
These multiples are called optical harmonics. The Hsieh group's experiment exploited the fact that changes in the symmetry of a crystal will affect the strength of each harmonic differently.
"We found that light reflected at the second harmonic frequency revealed a set of symmetries completely different from those of the known crystal structure,
whereas this effect was completely absent for light reflected at the fundamental frequency, "says Hsieh."
#The world's fastest nanoscale photonics switch: Russian scientists developed the world's fastest nanoscale photonics switch This work belongs to the field of photonics-an optics discipline
which appeared in the 1960-s, simultaneously with the invention of lasers. Photonics has the same goals as electronics does,
but uses photons--the quanta of light--instead of electrons. The biggest advantage of using photons is the absence of interactions between them.
As a consequence, photons address the data transmission problem better than electrons. This property can primarily be used for in computing where IPS (instructions per second) is the main attribute to be maximized.
The typical scale of eletronic transistors--the basis of contemporary electronic devices--is less than 100 nanometers
Nanoparticles were fabricated in the Australian National University by e-beam lithography followed by plasma-phase etching.
and all the experimental work was carried out at the Faculty of physics of Lomonosov Moscow State university, in the Laboratory of Nanophotonics and Metamaterials."
--We used our femtosecond laser complex acquired as part of the MSU development program"."Eventually, researches developed a"device":
--Free carriers (electrons and electron holes) place serious restrictions on the speed of signal conversion in the traditional integrated photonics.
Features of the technology implemented in our work will allow its use in silicon photonics. In the nearest future, we are going to test such nanoparticles in integrated circuits
Commonly, femtosecond-short shutter speeds are provided by short-pulse laser technology, but laser light is not able to spatially resolve atoms.
Scientists from the Laboratory for Attosecond Physics at LMU and MPQ have succeeded now in producing ultrashort electron pulses with a duration of only 28 femtoseconds.
Due to this short wavelength, it is possible to visualize even single atoms in diffraction experiments. If such electrons meet a molecule or atom,
they are diffracted into specific directions due to their short wavelength. This way they generate an interference pattern at the detector from
the physicists applied their ultrashort electron pulses to a biomolecule in a diffraction experiment. It is planned to use those electron beams for pump-probe experiments:
an optical laser pulse is sent to the sample, initiating a response. Shortly afterwards the electron pulses produce a diffraction image of the structure at a sharp instant in time.
A large amount of such snapshots at varying delay times between the initiating laser pulses and the electron pulses then results in a film showing the atomic motion within the substance.
Thanks to the subatomic wavelength of the electrons, one therefore obtains a spatial image as well as the dynamics.
Altogether this results in a four-dimensional impression of molecules and their atomic motions during a reaction. ith our ultrashort electron pulses
The aim of the scientists is to eventually observe even the much faster motions of electrons in light-driven processes o
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