Butterfly wing optics is helpful to make bright and realistic holograms at low cost.

Rajesh Menon, an associate professor of electronic and computer engineering at the University of Utah, showed a new two-dimensional hologram, which can be displayed with a flashlight. His team found a cheap way to make full-color two-dimensional and three-dimensional holograms, which are more realistic and brighter than the current holograms and can be viewed from a wider angle. (Dan hickson/College of Engineering, University of Utah) Holograms have long attracted the public's imagination. Whether the fans of Star Wars dream of holographic information and chess games, or the awe-inspiring concert audience standing in front of the resurrected Tupac shakoor, or the holographic future envisaged in the upcoming Black Blade 2049, the holographic concept seems to provide something for everyone.

However, despite the modern development, laser holography technology since the 1960s, the only holograms that most of us encounter today are fuzzy security images on credit cards or dim lights that occasionally appear in science museums.

Now a team of engineers at the University of Utah claims to have developed a game-changing technology, which can produce photo-realistic three-dimensional holograms cheaply, with only one flashlight. In a paper published in Science Report, researchers explained how they used complex three-dimensional nanostructures to make colorful and bright holograms. Maybe one day, these holograms will become a reality in daily life.

In order to understand how today's hologram technology works, it is helpful to compare it with the conventional hologram. A camera uses a lens and a natural light source to record light emitted from a scene on a photographic medium. The result is to faithfully match the two-dimensional image of the original scene from a specific angle or favorable position.

Related: Nano-holographic technology brings 3D images to mobile phones, tablets and televisions.

However, a hologram is a three-dimensional record of the total light field generated by an object. To capture the scattered light field, a powerful light source like laser is needed, which is divided and oriented by a mirror and hits the object from all directions.

Ordinary holograms record light fields on a chemical medium similar to photographic paper. To the naked eye, it is just a random collection of points and lines. In order to actually produce a holographic image, another laser beam is needed to shine on or pass through the recorded hologram. Rajesh Menon, an associate professor of electronic and computer engineering at the University of Utah and the lead author of this new paper, said that the generated ghostly floating images can be viewed from multiple angles.

Traditional holographic technology has some serious limitations. First of all, the holograms produced by these laser systems are so dim that they can only be seen clearly in a dark room. Secondly, if you want a hologram with multiple colors, each color needs a laser, which will soon become expensive. In addition, the mass-produced sticker holograms used for anti-counterfeiting also have some problems, which are distorted by rainbow flicker effect.

The new technology developed by Menon and his team seems to solve all these problems and greatly reduce the production and display costs. The magic lies in holographic recording, which is a transparent plastic sheet with a three-dimensional nanostructure composed of tiny hills and valleys. The nano-scale form of hologram does not absorb white light, but only reflects some wavelengths of light, but is used to manipulate and adjust light to produce bright light, a full-color 3D image of a simple flashlight.

This technique is similar to the evolutionary adaptation of some butterfly species. Colors in nature are usually the products of pigments absorbing some wavelengths of light and reflecting other wavelengths of light. But these butterflies enhance the brightness of their rainbow-like wings by reflecting light on a microscopic scale instead of absorbing it. Because some wavelengths are cancelled by rough interference, a bright pure blue color is reflected back to the observer.

Related: Breakthroughs in nanotechnology can produce real holograms.

Menon explained that his computer-generated microstructure has a similar purpose, improving the efficiency and brightness of holograms by changing the direction of light instead of absorbing it.

"We remove the color of all the light that comes in and basically replace it a little," he said, thinking that we were creating an American flag. I think it's red here, blue there and white elsewhere. I can design my structure and substitute colors very effectively.

Because three-dimensional nanostructures can be printed on ordinary plastics, the cost of copying holograms is relatively low, similar to the mass production of CDs or DVDs. This may contribute to the competition of Menon Holography in the securities market. Menon said that unlike the rainbow stripe stickers on credit cards and driver's licenses, we will soon get real photo holograms that are more difficult to forge.

Although the paper only describes the production of two-dimensional holograms, his team has successfully produced static three-dimensional holograms with the same technology. But he didn't take his eyes off the ultimate goal. This is a completely moving interactive hologram, which stands out directly from science fiction. He said that this preliminary study has pointed out the way forward, but many engineering challenges still exist.

"In order to create a dynamic image, you need to be able to change the imprint pattern as a function of time," Menon said. We can borrow some technologies to achieve this, but they need some improvement.

Menon started a private company called PointSpectrum and continued to develop holographic technology. He hopes that this technology will soon compete with bulky virtual reality headphones and provide immersive holographic experience theaters and schools in theme parks and movies.

Originally published in The Explorer.