Recently, the MIT Photonics and Modern Electromagnetics Research Group has made major breakthroughs in the field of light wave conduction and control. They have pioneered the control mechanism of the light wave conduction direction. Research results have been published in the latest issue of the top scientific journal "Science" magazine. . The scholars of the Department of Information and Electronic Engineering of Zhejiang University also provided important support for the study.

According to a reporter from China Economic Net, this research, known as “Directional Selective Filter,” is part of the MIT Solid State Photovoltaic Battery project. One of the more important parts of the project's potential application areas is the transformation of industrial solar panels, which will increase the power generation efficiency from the current 15% to 80-90%. MIT scholars collaborated with Zhejiang University to develop an effective material system for the first time so that light can only be transmitted from a certain direction into the material, and light transmitted from other directions will be reflected. It ensures that the absorbed light waves will not be scattered and lost to maximize the absorption and storage of light by the solar panel.

Solid State Photovoltaic Battery

This kind of material system is made up of two different extremely thin materials and the thickness of each layer can be precisely controlled. Professor of the research group said: "Normally, when light hits the interface between two materials, reflection occurs. However, there is a magical angle called Brewster's angle, when the light is just incident from the Brewster angle, the material There will be no reflection on the interface."

Shen Yichen, Ph.D., a third-year Ph.D. student in the Department of Applied Physics at the Massachusetts Institute of Technology, said: “Although only a small portion of light is reflected at each material interface, when a material system has a multilayer structure, the light is The superposition of reflections at each interface allows most of the light to be reflected, with the exception of the beam that travels along Brewster's corner. We used 80 material layers with precisely controlled thickness to achieve a choice of all visible light band propagation directions."

Directional filter effect chart

According to a reporter from China Economic Net, the research has potential applications in photovoltaic cells, optical detection systems, and vehicle anti-jamming. Taking a photovoltaic cell as an example, the conventional solar photovoltaic cell panel is made of single crystal silicon. Monocrystalline silicon can only absorb the sunlight with a wavelength of less than 1.2 μm and convert it into electrical energy. This wavelength band only occupies the entire energy of sunlight. About 37% of the traditional solar panels are subject to the monolithic silicon's selectivity to light waves and thus have limited power generation efficiency. MIT's Solid State Photovoltaic Cell Project innovates the way sunlight is absorbed. First, all wavelengths of sunlight are incorporated into the absorber, and the helium is converted into a heat-heated absorber, which in turn controls the radiant energy of the absorber. The most effective use of the light wave band, so that the solar cell power generation efficiency has been qualitatively improved.

In addition, directional selective filters can also be applied to optical detection systems such as astronomical telescopes, microscopes, and cameras. When the camera is used to backlight the subject, selective filtering allows the camera to only accept light in the direction of the subject, thus avoiding strong light interference in other directions and capturing the subject clearly. In the aspect of anti-jamming of vehicles, if the vehicle windshield front window is made of a material that can select the light-wave transmission direction, it can effectively shield the strong light interference of the oncoming vehicles and reduce the incidence of traffic accidents. At present, the U.S. military is also discussing with scholars of MIT the possibility of applying direction-selective filters to fighter pilots against laser interference.

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