Next Generation of AR/VR Headsets (Quantglasses)

“Image” is everything in the $20 billion market for AR/VR glasses (Quantglasses). Consumers are looking for glasses that are compact and easy to wear, delivering high-quality imagery with socially acceptable optics that don’t look like “bug eyes.”

University of Rochester researchers at the Institute of Optics have come up with a novel technology to deliver those attributes with maximum effect. In a paper in Science Advances, they describe imprinting freeform optics with a nanophotonic optical element called “a metasurface.”

The metasurface is a veritable forest of tiny, silver, nanoscale structures on a thin metallic film that conforms, in this advance, to the freeform shape of the optics—realizing a new optical component the researchers call a metaform. The metaform is able to defy the conventional laws of reflection, gathering the visible light rays entering an AR/VR eyepiece from all directions, and redirecting them directly into the human eye.

 

Freeform optics is an emerging technology that uses lenses and mirrors with surfaces that lack an axis of symmetry within or outside the optics diameter to create optical devices that are lighter, more compact, and more effective than ever before.

Nick Vamivakas, a professor of quantum optics and quantum physics, likened the nanoscale structures to small-scale radio antennas.  “When we actuate the device and illuminate it with the right wavelength, all of these antennas start oscillating, radiating a new light that delivers the image we want downstream.

Metasurfaces are also called ‘flat optics’ so writing metasurfaces on freeform optics is creating an entirely new type of optical component,” says Jannick Rolland, the Brian J. Thompson Professor of Optical Engineering and director of the Center for Freeform Optics.

Adds Rolland, “This kind of optical component can be applied to any mirrors or lenses, so we are already finding applications in other types of components” such as sensors and mobile cameras.

The first demonstration required many years to complete.

The goal is to direct the visible light entering the AR/VR glasses to the eye. The new device uses a freespace optical combiner to help do that. However, when the combiner is part of freeform optics that curve around the head to conform to an eyeglass format, not all of the light is directed to the eye. Freeform optics alone cannot solve this specific challenge. That’s why the researchers had to leverage a metasurface to build a new optical component.

Integrating these two technologies, freeform and metasurfaces, understanding how both of them interact with light, and leveraging that to get a good image was a major challenge,” says lead author Daniel Nikolov, an optical engineer in Rolland’s research group.

Source: https://www.rochester.edu/

VR Headset The Size Of A Pair Of Large Sunglasses

For all the advancements in virtual reality technology in recent years, one major factor still holding the space back is the size and relative discomfort of current headset design. Even the most compact and comfortable VR headsets today still resemble something like a cross between ski goggles and a motorcycle helmet, requiring massive headstraps to secure a heavy display that protrudes multiple inches away from the face. Reference designs for “eyeglasses” style VR displays help a bit, but they still look like coke-bottle spectacles from a steampunk cosplay event (and provide a limited field of view, to boot).

Now, researchers at Facebook Reality Labs are using holographic film to create a prototype VR display that looks less like ski goggles and more like lightweight sunglasses. With a total thickness less than 9mm—and without significant compromises on field of view or resolution—these displays could one day make today’s bulky VR headset designs completely obsolete. In the newly published ACM Siggraph paper Holographic Optics for Thin and Lightweight Virtual Reality, researchers Andrew Maimone and Junren Wang detail the optics behind their lightweight prototype. The key to the thinness is a series of flat, polarized films that use a “pancake opticslight-folding technique to reflect the displayed image multiple times in a small space. That design effectively extends the apparent focal length of the image (which is key to user eye comfort) without the need for a large physical space for the light to travel through. Holographic films used to focus the image onto the eye also eliminate the need for the kinds of bulky refractive lensing systems found in current headsets.

Source: https://arstechnica.com/

3D Printed Metamaterials With Super Optical Properties

A team of engineers at Tufts University has developed a series of 3D printed metamaterials with unique microwave or optical properties that go beyond what is possible using conventional optical or electronic materials. The fabrication methods developed by the researchers demonstrate the potential, both present and future, of 3D printing to expand the range of geometric designs and material composites that lead to devices with novel optical properties. In one case, the researchers drew inspiration from the compound eye of a moth to create a hemispherical device that can absorb electromagnetic signals from any direction at selected wavelengths.

The geometry of a moth’s eye provides inspiration for a 3D printed antenna that absorbs specific microwave frequencies from any direction

Metamaterials extend the capabilities of conventional materials in devices by making use of geometric features arranged in repeating patterns at scales smaller than the wavelengths of energy being detected or influenced. New developments in 3D printing technology are making it possible to create many more shapes and patterns of metamaterials, and at ever smaller scales. In the study, researchers at the Nano Lab at Tufts describe a hybrid fabrication approach using 3D printing, metal coating and etching to create metamaterials with complex geometries and novel functionalities for wavelengths in the microwave range. For example, they created an array of tiny mushroom shaped structures, each holding a small patterned metal resonator at the top of a stalk. This particular arrangement permits microwaves of specific frequencies to be absorbed, depending on the chosen geometry of the “mushrooms” and their spacing. Use of such metamaterials could be valuable in applications such as sensors in medical diagnosis and as antennas in telecommunications or detectors in imaging applications.

The research has been published in the journal Microsystems & Nanoengineering (Springer Nature).

Source: https://now.tufts.edu/

How To Arrange Nanoparticules With a Vinaigrette

Materials scientists at Duke University have theorized a new “oil-and-vinegar” approach to engineering self-assembling materials of unusual architectures made out of spherical nanoparticles. The resulting structures could prove useful to applications in optics, plasmonics, electronics and multi-stage chemical catalysis. Left to their own tendencies, a system of suspended spherical nanoparticles designed to clump together will try to maximize their points of contact by packing themselves as tightly as possible. This results in the formation of either random clusters or a three-dimensional, crystalline structure.

But materials scientists often want to build more open structures of lower dimensions, such as strings or sheets, to take advantage of certain phenomena that can occur in the spaces between different types of particles.  In the new study, Gaurav Arya, associate professor of mechanical engineering and materials science at Duke, proposes a method that takes advantage of the layers formed by liquids that, like a bottle of vinaigrette left on the shelf for too long, refuse to mix together.

When spherical nanoparticles are placed into such a system, they tend to form a single layer at the interface of the opposing liquids. But they don’t have to stay there. By attachingoil” or “vinegarmolecules to the particles’ surfaces, researchers can make them float more on one side of the dividing line than the other.

The particles want to maximize their number of contacts and form bulk-like structures, but at the same time, the interface of the different liquids is trying to force them into two layers,” said Arya. “So you have a competition of forces, and you can use that to form different kinds of unique and interesting structures.”

Arya’s idea is to precisely control the amount that each spherical nanoparticle is repelled by one liquid or the other. And according to his calculations, by altering this property along with others such as the nanoparticles’ composition and size, materials scientists can make all sorts of interesting shapes, from spindly molecule-like structures to zig-zag structures where only two nanoparticles touch at a time. One could even imagine several different layers working together to arrange a system of nanoparticles.

In the proof-of-concept paper, the nanoparticles could be made out of anything. Gold or semiconductors could be useful for plasmonic and electrical devices, while other metallic elements could catalyze various chemical reactions. The opposing substrates that form the interface, meanwhile, are modeled after various types of polymers that could also be used in such applications.

The novel approach appeared online on March 25 in the journal ACS Nano.

Source: https://pratt.duke.edu/

Optical Circuits Up To 100 Times Faster Than Electronic Circuits

Optical circuits are set to revolutionize the performance of many devices. Not only are they 10 to 100 times faster than electronic circuits, but they also consume a lot less power. Within these circuits, light waves are controlled by extremely thin surfaces called metasurfaces that concentrate the waves and guide them as needed. The metasurfaces contain regularly spaced nanoparticles that can modulate electromagnetic waves over sub-micrometer wavelength scales.

Metasurfaces could enable engineers to make flexible and ultra-thin optics for a host of applications, ranging from flexible tablet computers to solar panels with enhanced light-absorption characteristics. They could also be used to create flexible sensors for direct placement on a patient’s skin, for example, in order to measure things like pulse and blood pressure or to detect specific chemical compounds.

The catch is that creating metasurfaces using the conventional method, lithography, is a fastidious process that takes several hours and must be done in a cleanroom. But EPFL engineers from the Laboratory of Photonic Materials and Fiber Devices (FIMAP) in Switzerland have now developed a simple method for making them in just a few minutes at low temperatures—or sometimes even at room temperature—with no need for a cleanroom. The EPFL‘s School of Engineering method produces dielectric glass metasurfaces that can be either rigid or flexible. The results of their research appear in Nature Nanotechnology.

The new method employs a natural process already used in : dewetting. This occurs when a thin film of material is deposited on a substrate and then heated. The heat causes the film to retract and break apart into tiny nanoparticles.

Dewetting is seen as a problem in manufacturing—but we decided to use it to our advantage,” says Fabien Sorin, the study’s lead author and the head of FIMAP.

With their method, the engineers were able to create dielectric glass metasurfaces, rather than metallic metasurfaces, for the first time. The advantage of dielectric metasurfaces is that they absorb very little light and have a high refractive index, making it possible to modulate the light that propagates through them.

Source: https://phys.org/

How To Shrink Objects To The Nanoscale

MIT researchers have invented a way to fabricate nanoscale 3-D objects of nearly any shape. They can also pattern the objects with a variety of useful materials, including metals, quantum dots, and DNA.

MIT engineers have devised a way to create 3-D nanoscale objects by patterning a larger structure with a laser and then shrinking it. This image shows a complex structure prior to shrinking.

It’s a way of putting nearly any kind of material into a 3-D pattern with nanoscale precision,” says Edward Boyden, the Y. Eva Tan Professor in Neurotechnology and an associate professor of biological engineering and of brain and cognitive sciences at MIT. Using the new technique, the researchers can create any shape and structure they want by patterning a polymer scaffold with a laser. After attaching other useful materials to the scaffold, they shrink it, generating structures one thousandth the volume of the original.

These tiny structures could have applications in many fields, from optics to medicine to robotics, the researchers say. The technique uses equipment that many biology and materials science labs already have, making it widely accessible for researchers who want to try it. Boyden, who is also a member of MIT’s Media Lab, McGovern Institute for Brain Research, and Koch Institute for Integrative Cancer Research, is one of the senior authors of the paper, which appears in the Dec. 13 issue of Science. The other senior author is Adam Marblestone, a Media Lab research affiliate, and the paper’s lead authors are graduate students Daniel Oran and Samuel Rodriques.

As they did for expansion microscopy, the researchers used a very absorbent material made of polyacrylate, commonly found in diapers, as the scaffold for their nanofabrication process. The scaffold is bathed in a solution that contains molecules of fluorescein, which attach to the scaffold when they are activated by laser light.

Using two-photon microscopy, which allows for precise targeting of points deep within a structure, the researchers attach fluorescein molecules to specific locations within the gel. The fluorescein molecules act as anchors that can bind to other types of molecules that the researchers add.

You attach the anchors where you want with light, and later you can attach whatever you want to the anchors,” Boyden says. “It could be a quantum dot, it could be a piece of DNA, it could be a gold nanoparticle.” “It’s a bit like film photography — a latent image is formed by exposing a sensitive material in a gel to light. Then, you can develop that latent image into a real image by attaching another material, silver, afterwards. In this way implosion fabrication can create all sorts of structures, including gradients, unconnected structures, and multimaterial patterns,” Oran explains.

Source: http://news.mit.edu/

 

How To Replace The Thick Glass Lenses by 2D Metalens

In optics, the era of glass lenses may be waning. In recent years, physicists and engineers have been designing, constructing and testing different types of ultrathin materials that could replace the thick glass lenses used today in cameras and imaging systems. Critically, these engineered lenses — known as metalenses — are not made of glass. Instead, they consist of materials constructed at the nanoscale into arrays of columns or fin-like structures. These formations can interact with incoming light, directing it toward a single focal point for imaging purposes.

But even though metalenses are much thinner than glass lenses, they still rely on “high aspect ratio” structures, in which the column or fin-like structures are much taller than they are wide, making them prone to collapsing and falling over. Furthermore, these structures have always been near the wavelength of light they’re interacting with in thickness — until now. In a paper published in the journal Nano Letters, a team from the University of Washington (UW) and the National Tsing Hua University in Taiwan announced that it has constructed functional metalenses that are one-tenth to one-half the thickness of the wavelengths of light that they focus. Their metalenses, which were constructed out of layered 2D materials, were as thin as 190 nanometers — less than 1/100,000ths of an inch thick.

This is the first time that someone has shown that it is possible to create a metalens out of 2D materials,” said senior and co-corresponding author Arka Majumdar, a UW assistant professor of physics and of electrical and computer engineering.

Their design principles can be used for the creation of metalenses with more complex, tunable features, added Majumdar, who is also a faculty researcher with the UW’s Molecular Engineering & Sciences Institute and Institute for Nano-Engineered Systems.

Source: https://www.washington.edu/

A stamp-sized nanofilm stores more data than 200 DVDs

Ninety percent of the world’s data has been created in the last two years, with a massive 2.5 quintillion bytes generated every single day. As you might suspect, this causes some challenges when it comes to storage. While one option is to gradually turn every square inch of free land into giant data centers, researchers from the  Center for Advanced Optoelectronic Functional Material Research, Northeast Normal University (China) may have come up with a more elegant solution. In a potential breakthrough, they have developed a new nanofilm80 times thinner than a human hair — that is able to store large amounts of data holographically. A single 10-by-10 cm piece of this film could archive more than 1,000 times the amount of data found on a DVD. By our count, that means around 8.5 TB of data. This data can also be retrieved incredibly quickly, at speeds of up to 1GB per second: The equivalent of 20 times the reading speed of modern flash memory.

In the journal Optical Materials Express, the researchers detail the fabrication process of the new film. This involves using a laser to write information onto silver nanoparticles on a titanium dioxide (titania) semiconductor film. This stores the data in the form of 3D holograms, thereby allowing it to be compressed into smaller spaces than regular optical systems.

That’s exciting enough, but what really makes the work promising is the fact that the data is stored in a way that is stable. Previous attempts at creating films for holographic data storage have proven less resilient than alternate storage methods since they can be wiped by exposure to ultraviolet light. That makes them less-than-viable options for long-term information storage. The creators of this new film, however, have shown that it has a high stability even in the presence of such light. This environmental stability means that the device could be used outside — or even conceivably in harsher radiation conditions like outer space.

Going forward, the researchers aim to test their new film by putting it through its paces outdoors. Should all go according to plan, it won’t be too long before this is available on the market. We might be willing to throw down a few bucks on Kickstarter for a piece!

Source: https://www.osapublishing.org
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