Lenses made from nanomaterials get closer to replacing glass

The latest ultrathin "metalenses" can now handle multiple colors.

Harvard SEAS

Researchers recently showed off breakthrough nanomaterial "metalenses" that could replace bulky glass optics. There was one problem, though -- it only worked on a single color at a time, meaning your smartphone could only do arty, monochromatic photos. However, the same team at Harvard's School of Engineering and Applied Sciences (SEAS), has unveiled a new material that works on a spectrum of colors from blue to green, opening up potential applications in specotroscopy, sensing and imaging.

As before, the metalenses are made up of sub-hair-width sized "nanopillars" made from titanium dioxide. By arranging them in specific patterns, they refract light towards a common focal point like a regular lens. Unlike glass optics, however, the materials are ultra-thin. That could one day lead to much less bulky cameras, smartphones and eyeglasses, to name a few applications.

By tweaking the shapes and patterns of the nanopillars, the Harvard team eliminated "chromatic aberration" or color fringing that normally requires bulky optics to fix. The end result is an ultrathin material without optical flaws than could potentially be manufactured more cheaply than a glass lens. "This platform is based on single step lithography and is compatible with high throughput manufacturing techniques such as nano-imprinting," says PhD student and co-first author Zhujun Shi.

Metalenses also have the potential to resolve finer detail than regular lenses, down to 400 nanometers. Though limited to wavelengths between 490 to 550 nanometers (blue to green, roughly), that makes the latest materials suitable for scientific instruments as well as specific types of imaging. Obviously, it won't work for cameras until it can handle the complete spectrum of light from red to violet, around 390 to 700 nanometers. Once that happens, it'll be a game-changer for devices of all kinds.