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The law of light refraction and reflection is the basis of geometric optics. However, Harvard University physicists used a series of experiments to demonstrate that the propagation of light does not obey these classical laws. This means that maybe one day when you look at your face with a flat mirror, you see a distortion effect of a magic mirror.
Light travels in different media at different speeds. When a beam of light strikes the water obliquely from the air, the direction of propagation of the beam changes. This is the so-called refraction phenomenon. Its exact expression, the law of refraction, was established many years ago by physicist Snell, mathematician Cartesian, and Fermat. This law shows that the angle of refraction of light at the interface is determined only by the speed of light propagation in the two materials. The reflection law found by Euclid as early as in ancient Greece was simpler: the reflection angle of light was equal to the angle of incidence.
Classical reflection and refraction laws naturally consider an interface as merely the ideal boundary between two substances. In other words, two media, rather than their cross sections, affect the propagation of light. The innovation of Harvard researchers is that the interface can be a factor in determining the spread of light. Their experiments show that a well-designed interface can intervene in the spread of light.
The researchers used a thin metal array at the interface between the silicon wafer and the air to demonstrate a series of violations of the classic reflection and refraction laws. Each element in this array resembles a tiny English letter “Vâ€, which is much smaller in size and spacing than the wavelength of light and the size of the incident beam cross-section. These "V"-shaped elements have different sizes, angles, and orientations. This design is to control the interaction time of light waves and different elements: Each metal "V" resembles a light trap that can "trap" light waves. Releasing it for some time.
The design of the array causes this "trapped" time to increase linearly from right to left along the interface so that even with normal incidence, different portions of the beam experience different time delays and the transmitted and reflected beams no longer propagate perpendicular to the interface. When the light is incident at an oblique angle, according to different “interface†designs, the reflected and refracted light can be manipulated in any direction. The reflection angle is not necessarily equal to the angle of incidence, and the reflected light can even be “bounced†back toward the light source instead of being deflected away from the light source as is generally the case. This is why the mirror can have the effect of a magic mirror.
This achievement was published on the 2nd issue of the "Science" magazine in the United States on the 2nd. The first author is currently doing post-doctoral research in Harbin University of Engineering and Applied Science. He graduated from the Department of Electronics, Peking University, in 2004 in the south of Anhui Province, in 2009. Received a Ph.D. from Harvard University.
Using the interface to control the delay of different parts of the beam is an innovative concept. Minnan told Xinhua News Agency reporters that they have used this artificial interface to create “light vortexâ€. This strange light beam spirals forward in space and can therefore be used to manipulate the rotation of tiny suspended particles. He predicted that this concept will lead to a series of useful optical components, such as ultra-thin, flat focus lenses that can correct the difference, and solar concentrators that can capture a wide range of incident sunlight. Harvard University has filed a patent application for this result. (Reporter Ren Haijun)
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