- 3369 - CAMERAS - how small can they get? Cameras keep on getting smaller and smaller, and the latest to appear is the same size as a grain of salt. And, it's able to produce images of much better quality than a lot of other ultra-compact cameras. You will never be able to hide now!
--------------------- 3369 - CAMERAS - how small can they get?
- Using a technology known as a metasurface, which is covered with 1.6 million cylindrical posts, the camera is able to capture full-color photos that are as good as images snapped by conventional lenses some half a million times bigger than this camera.
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- And the super-small camera has the potential to be helpful in helping miniature soft robots explore the world, to giving experts a better idea of what's going on deep inside the human body.
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- One of the camera's special tricks is the way it combines hardware with computational processing to improve the captured image. Signal processing algorithms use machine learning techniques to reduce blur and other distortions that otherwise occur with cameras this size. The camera effectively uses software to improve its vision.
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- Further down the line, those algorithms could be used for more than just image enhancement. They could be deployed to automatically detect particular objects that the camera is looking for, like signs of disease inside the human body.
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- That processing is added to the metasurface construction that replaces the usual curved glass or plastic lenses with a material a mere half a millimeter wide. Each of the 1.6 million cylindrical posts was individually designed to best capture what's in front of the camera, with computational modeling used to work out the optimal configuration.
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- The glass-like silicon nitride that the metasurface is made from is a material that fits in with conventional electronics manufacturing processes, which means that it shouldn't be too difficult to scale up production of these super-tiny cameras using procedures and equipment that's already in place.
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- So while there's still plenty of work to do to get this from the lab to a commercial production line, the signs are good that it's possible. Once that's done, we'll have access to super-small cameras that can actually take a decent picture.
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- There is another potential use for miniature cameras such as this is using them as a covering layer to turn entire surfaces into cameras, removing the need for a conventional camera above a laptop screen or on the back of a smartphone.
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- We could turn individual surfaces into cameras that have ultra-high resolution, so you wouldn't need three cameras on the back of your phone anymore, but the whole back of your phone would become one giant camera.
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- We can think of completely different ways to build devices in the future. Can you imagine how much trouble this capability is going to get us in to? There is no such thing as privacy anymore.
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-cientists have developed a photoelectrode that can harvest 85 percent of visible light in a 30 nanometers-thin semiconductor layer between gold layers, converting light energy 11 times more efficiently than previous methods.
In the pursuit of realizing a sustainable society, there is an ever-increasing demand to develop revolutionary solar cells or artificial photosynthesis systems that utilize visible light energy from the sun while using as few materials as possible.
The research team, led by Professor Hiroaki Misawa of the Research Institute for Electronic Science at Hokkaido University, has been aiming to develop a photoelectrode that can harvest visible light across a wide spectral range by using gold nanoparticles loaded on a semiconductor. But merely applying a layer of gold nanoparticles did not lead to a sufficient amount of light absorption, because they took in light with only a narrow spectral range.
In the study published in Nature Nanotechnology, the research team sandwiched a semiconductor, a 30-nanometer titanium dioxide thin-film, between a 100-nanometer gold film and gold nanoparticles to enhance light absorption. When the system is irradiated by light from the gold nanoparticle side, the gold film worked as a mirror, trapping the light in a cavity between two gold layers and helping the nanoparticles absorb more light.
To their surprise, more than 85 percent of all visible light was harvested by the photoelectrode, which was far more efficient than previous methods. Gold nanoparticles are known to exhibit a phenomenon called localized plasmon resonance which absorbs a certain wavelength of light. "Our photoelectrode successfully created a new condition in which plasmon and visible light trapped in the titanium oxide layer strongly interact, allowing light with a broad range of wavelengths to be absorbed by gold nanoparticles," says Hiroaki Misawa.
When gold nanoparticles absorb light, the additional energy triggers electron excitation in the gold, which transfers electrons to the semiconductor. "The light energy conversion efficiency is 11 times higher than those without light-trapping functions," Misawa explained. The boosted efficiency also led to an enhanced water splitting: the electrons reduced hydrogen ions to hydrogen, while the remaining electron holes oxidized water to produce oxygen—a promising process to yield clean energy.
"Using very small amounts of material, this photoelectrode enables an efficient conversion of sunlight into renewable energy, further contributing to the realization of a sustainable society," the researchers concluded.
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-e search for clean energy alternatives to fossil fuels, one promising solution relies on photoelectrochemical (PEC) cells—water-splitting, artificial-photosynthesis devices that turn sunlight and water into solar fuels such as hydrogen.
In just a decade, researchers in the field have achieved great progress in the development of PEC systems made of light-absorbing gold nanoparticles—tiny spheres just billionths of a meter in diameter—attached to a semiconductor film of titanium dioxide nanoparticles (TiO2 NP). But despite these advancements, researchers still struggle to make a device that can produce solar fuels on a commercial scale.
Now, a team of scientists led by the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has gained important new insight into electrons' role in the harvesting of light in gold/TiO2 NP PEC systems. The scientists say that their study, recently published in the Journal of Physical Chemistry Letters, can help researchers develop more efficient material combinations for the design of high-performance solar fuels devices.
"By quantifying how electrons do their work on the nanoscale and in real time, our study can help to explain why some water-splitting PEC devices did not work as well as hoped," said senior author Oliver Gessner, a senior scientist in Berkeley Lab's Chemical Sciences Division.
And by tracing the movement of electrons in these complex systems with chemical specificity and picosecond (trillionths of a second) time resolution, the research team members believe they have developed a new tool that can more accurately calculate the solar fuels conversion efficiency of future devices.
Electron-hole pairs: A productive pairing comes to light
Researchers studying water-splitting PEC systems have been interested in gold nanoparticles' superior light absorption due to their "plasmonic resonance"—the ability of electrons in gold nanoparticles to move in sync with the electric field of sunlight.
"The trick is to transfer electrons between two different types of materials—from the light-absorbing gold nanoparticles to the titanium-dioxide semiconductor," Gessner explained.
When electrons are transferred from the gold nanoparticles into the titanium dioxide semiconductor, they leave behind "holes." The combination of an electron injected into titanium dioxide and the hole the electron left behind is called an electron-hole pair. "And we know that electron-hole pairs are critical ingredients to enabling the chemical reaction for the production of solar fuels," he added.
But if you want to know how well a plasmonic PEC device is working, you need to learn how many electrons moved from the gold nanoparticles to the semiconductor, how many electron-hole pairs are formed, and how long these electron-hole pairs last before the electron returns to a hole in the gold nanoparticle. "The longer the electrons are separated from the holes in the gold nanoparticles—that is, the longer the lifetime of the electron-hole pairs—the more time you have for the chemical reaction for fuels production to take place," Gessner explained.
To answer these questions, Gessner and his team used a technique called "picosecond time-resolved X-ray photoelectron spectroscopy (TRXPS)" at Berkeley Lab's Advanced Light Source (ALS) to count how many electrons transfer between the gold nanoparticles and the titanium-dioxide film, and to measure how long the electrons stay in the other material. Gessner said his team is the first to apply the X-ray technique for studying this transfer of electrons in plasmonic systems such as the nanoparticles and the film. "This information is crucial to develop more efficient material combinations."
An electronic 'count'-down with TRXPS
Using TRXPS at the ALS, the team shone pulses of laser light to excite electrons in 20-nanometer (20 billionths of a meter) gold nanoparticles (AuNP) attached to a semiconducting film made of nanoporous titanium dioxide (TiO2).
The team then used short X-ray pulses to measure how many of these electrons "traveled" from the AuNP to the TiO2 to form electron-hole pairs, and then back "home" to the holes in the AuNP.
"When you want to take a picture of someone moving very fast, you do it with a short flash of light—for our study, we used short flashes of X-ray light," Gessner said. "And our camera is the photoelectron spectrometer that takes short 'snapshots' at a time resolution of 70 picoseconds."
The TRXPS measurement revealed a few surprises: They observed two electrons transfer from gold to titanium dioxide—a far smaller number than they had expected based on previous studies. They also learned that only one in 1,000 photons (particles of light) generated an electron-hole pair, and that it takes just a billionth of a second for an electron to recombine with a hole in the gold nanoparticle.
Altogether, these findings and methods described in the current study could help researchers better estimate the optimal time needed to trigger solar fuels production at the nanoscale.
"Although X-ray photoelectron spectroscopy is a common technique used at universities and research institutions around the world, the way we expanded it for time-resolved studies and used it here is very unique and can only be done at Berkeley Lab's Advanced Light Source," said Monika Blum, a co-author of the study and research scientist at the ALS.
"Monika's and Oliver's unique use of TRXPS made it possible to identify how many electrons on gold are activated to become charge carriers—and to locate and track their movement throughout the surface region of a nanomaterial—with unprecedented chemical specificity and picosecond time resolution," said co-author Francesca Toma, a staff scientist at the Joint Center for Artificial Photosynthesis (JCAP) in Berkeley Lab's Chemical Sciences Division. "These findings will be key to gaining a better understanding of how plasmonic materials can advance solar fuels."
The team next plans to push their measurements to even faster time scales with a free-electron laser, and to capture even finer nanoscale snapshots of electrons at work in a PEC device when water is added to the mix.
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-Photons are the basis for many next-generation quantum technologies, including ultra-secure quantum communications and potentially game-changing quantum computers.
That's because these light particles can be entangled or placed in a superposition—two quantum states that enable quantum technologies.
But to create these states, researchers need to work with extremely non-classical kinds of light that have a small number of photons, or even just one photon. That can be a difficult task requiring a complicated setup, as typical sources of light (like a laser) generate states where there is always some possibility of having a large number of photons.
Theorists at the Pritzker School of Molecular Engineering (PME) at the University of Chicago have developed a new scheme for trapping single photons in a cavity. Their mechanism allows two sources to emit the selected number of photons into a cavity before destructive interference cancels out both sources, essentially creating a "wall" that prevents further photons from entering.
This new mechanism could provide a simpler way to create quantum light without using the complicated materials and systems that are usually required.
The research, led by Prof. Aashish Clerk with graduate students Andrew Lingenfelter and David Roberts, was published Nov. 26 in Science Advances.
Creating a 'wall' of interference
Typical systems for trapping single photons in a cavity involve using materials that have an extremely large optical nonlinearity, which forces photons in the cavity to interact with one another strongly. In such systems, the cavity's resonance frequency can be strongly shifted by adding even just one photon. If one then shines a laser on the cavity, one photon can enter, but not a second (because of the frequency shift produced by the first photon).
The problem with this mechanism is that it requires extremely large optical nonlinearities and very low dissipation, a combination that is extremely difficult if not impossible to achieve in most platforms.
The system proposed by Clerk's research team uses two different sources to simultaneously emit photons into a cavity that has an extremely weak nonlinearity (far too weak for conventional approaches to work). With careful tuning, these sources then cancel each other out with destructive interference—creating a "wall" that blocks photons—once the selected number of photons are captured in the cavity.
The potential applications are wide-ranging. Using destructive interference in this way means the system doesn't have to use special optically nonlinear materials, which opens the door to for several different platforms, including as a tool for quantum simulation.
The basic mechanism can also be applied to all kinds of electromagnetic radiation, not just visible light. One exciting possibility is using it to generate and control microwave-frequency photons in a superconducting circuit. This could enable new ways to store and process quantum information. Clerk's group is currently working with experimentalists to implement this scheme to do just that.
He and his collaborators are even examining the system as a potential way to entangle photons, where observation of one photon automatically provides information about the photon it is entangled with, no matter how far apart they are.
"We think this scheme could work in a lot of different systems," Clerk said. "If you don't need special materials, it really expands the potential of light-based quantum technologies."
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December 5, 2021 CAMERAS - how small can they get? 3369
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