Metalenses: a technology that will change the world

In recent years, alternatives to glass lenses have begun to emerge, which have real potential to reach the general public. These alternatives are called metalenses (metalenses), and they will change the world

There are technologies that change everything we know about the possible and the impossible in everyday life. In this entry, I want to review one of these technologies, which is currently in its initial stages - but has the potential to fundamentally change our lives. And strangely, almost no one talks about her. Well, except for the World Economic Forum in its list of ten harmful technologies from 2019[1]. But try asking someone on the street about "meta-lenses" and chances are they won't have a clue what you're talking about.

So what exactly are metalenses? To answer the question, we first need to understand what lenses are in general, and what is the big problem with them in the industry.

Phones, computers and other electronic devices have undergone a continuous process of miniaturization in recent decades. Digital cameras have also been miniaturized, but at a slower pace. This is because in order to distort and distort the passage of light in such small devices, tiny lenses are needed carefully carved from glass, and the lens components themselves are often stacked on top of each other to focus the light properly.

In other words, we live in the 21st century, and still use the same technology for focusing light that was used in the 17th century (that's when the telescope was invented, or at least a patent was applied for)[2].

In recent years, alternatives to glass lenses have begun to emerge, which have real potential to reach the general public. These alternatives are called metalenses (metalenses), and they will change the world.

A meta-lens is based on a thin surface - much thinner than a human hair - whose surface has been burned with nanometric resolution. As a result, when light hits the surface, its properties change. Researchers have found ways to burn the surface in just the right patterns so that the properties of the light leaving the metalens can be selected. It is also possible to place a large number of metalenses, one on top of the other, in a minimal volume.

Two recent breakthroughs in the field bode well for metalenses. In 2018, researchers managed to solve the problem of chromatic aberration, which characterizes normal lenses. This problem describes a situation where white light passes through a normal glass lens, is refracted and split into many wavelengths, and some of them are refracted at different angles and focused at different distances from the lens. To deal with chromatic aberration, engineers today have to place lenses in space carefully and precisely. However, in 2018 there was success in the development of a single meta-lens that is able to concentrate all the wavelengths of white light at the same point[3]. Researchers have also succeeded in correcting other aberrations - such as astigmatism - which cause distortion and blurring of the resulting image.

The second breakthrough was published this very week (August 25, 2020) in the prestigious science journal PNAS. The researchers incorporated "nematic liquid crystals" into the meta-lens, and were thus able to control its properties through an electric field applied around it. They proved that the meta-lens is actually capable of functioning similarly to the human eye - or like a telescope or an elaborate camera, which is based on several lenses that are distant and close to each other in order to enlarge the image[4].

Say now - so what's the big deal? My smartphone also has the option to enlarge the image! But that is not the case. The smartphone has one tiny lens, and therefore it is not possible to perform a real "zoom" (optical), but only a digital one. Such a digital zoom does not really enrich the details of the image, but only enlarges it for appearance. If you try to enlarge it in this way, you will quickly find that the small details become blurred. You enlarge the image but lose the resolution.

The meta-lenses make it possible to overcome this problem, even without needing a number of large and expensive glass lenses, which have to move apart or move closer together. All that is needed is one metalens - of zero thickness - and an electric current. And that's it. That's enough to create a lens of unimaginable size that should (eventually) rival the most sophisticated cameras available today. Oh, and it should also be cheaper than regular lenses – at least once the technology matures – since these lenses can be manufactured using the same equipment currently used in the semiconductor industry. In fact, one chip will be processed in the same factory to contain electronic components and metalenses together.

None of this is to say that the metalenses are perfect. There are still challenges on the way to realizing the great promise inherent in them. The technology is so new that it is still necessary to understand exactly how to adapt the existing devices for it. They are also too small to absorb a large amount of light - but when you can produce and place thousands of lenses in the same space where one traditional lens was supposed to be, who cares? Together, they will absorb the same amount of light as the original lens. And when they can be placed anywhere else - on the entire back and front surface of the smartphone, for example - they will be much more effective than the poor single lens that your smartphone currently contains. Progress to these types of applications will take several more years, but we are already on our way there.

This is all well and good, but how will the metalenses change your life? in endless ways. Imagine a smart phone completely covered in metalenses capable of functioning as a sophisticated microscope, and identifying bacteria (or even viruses) in a single drop of water. At the push of a button, it can also turn into a telescope and photograph everything around you in high resolution and in 360 degrees. Think of drones covered with such meta-lenses, which can just as easily photograph the ground in high resolution from a height of hundreds - or thousands - of meters, or examine the water droplets in the clouds to understand their chemical composition.

Actually, why go so far? Just think about glasses that at the push of a button can turn into a telescope or a microscope, sunglasses or night vision goggles - and still look and feel exactly the same on the outside. I would buy these.

Think of a world where such cameras are everywhere - on every wall, on every surface - and together provide Google, or Facebook, or the Chinese government, with an understanding of everything that is happening in the world. No more prominent and cumbersome cameras, located on the walls of buildings in the streets, but invisible cameras that collect information all the time.

Even virtual (and augmented) reality devices will be able to leap forward thanks to metalenses. We can say goodbye to the huge black box that sits on our head, and replace it with glasses with tiny and smart projectors. And maybe even - who knows - also in contact lenses that function in a similar way.

So - have I convinced you yet that you need to know about metalenses?

[1] http://www3.weforum.org/docs/WEF_Top_10_Emerging_Technologies_2019_Report.pdf

[2] https://en.wikipedia.org/wiki/History_of_the_telescope

[3] https://www.nature.com/articles/s41566-018-0130-7

[4] https://www.pnas.org/content/117/34/20390

For the blog of Dr.Roey Tsezana, the guide to the future
* Dr.Roey Tsezana is a futures researcher and lecturer, author of the books "The Guide to the Future" and "The Rulers of the Future"

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