A flat lens creates the perfect image.



    Physicists from the Harvard School of Engineering and Applied Sciences (SEAS) created a flat lens with a diameter of 1 mm and a thickness of 60 nm, which refracts light waves in the same way as a normal bulk lens, but without optical distortion.

    To understand the principle of the new lens, you need to remember the school course of optics. A conventional lens changes the direction of light waves due to the phase delay effect at the interface of two media with different densities. Since the speed of light has a different value, this is where the phase delay arises.


    Animation of Oleg Alexandrov

    All traditional optics are built on such an effect, but not a new lens of Harvard physicists. Instead of using materials of different densities and with a special shape, they generate a phase delay using a precisely calculated grid of nanoantennas on a flat surface - the so-called metamaterial.



    The millimeter-size lens itself is made of silicon. With a thickness of 60 nanometers, the plate remains transparent. The surface is covered with a nanometer layer of gold, from which particles of the desired shape are etched and arranged in concentric circles. An antenna of each shape reacts with electromagnetic radiation at different lengths and creates a phase delay directly on the surface of the lens. The right side of the illustration shows the phase delay for each section. Thus, light does not need to pass through the thickness of an ordinary lens - and therefore many characteristic optical distortions disappear.

    According to a press release, it is possible to make such lenses for the "wide range: from infrared to terahertz", that is, from 1000 nm to 1 mm, if the size, angle and distance between the antennas are appropriately selected. It is assumed that in the first place the lens will find application in fiber optic routers.

    Note that the visible range of 740-380 nm does not fall into the aforementioned plug; it requires slightly smaller nanoantennas. But not far off is the time when a commercially available metamaterial of nanometer thickness will be created for visible light. The first prototypes of such metamaterial appeared several years ago. This is a completely revolutionary technology that can completely transform the optical industry.

    Scientists have published the results of their work in Nano Letters Magazine.

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