Performing optical logic operations by a diffractive neural network

By Chao Qian, Xiao Lin, Xiaobin Lin, Jian Xu, Yang Sun, Erping Li, Baile Zhang, Hongsheng Chen. Light: Science & Applications, 2020

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Optical logic operations lie at the heart of optical computing, and they enable many applications such as ultrahigh-speed information processing. However, the reported optical logic gates rely heavily on the precise control of input light signals, including their phase difference, polarization, and intensity and the size of the incident beams. Due to the complexity and difficulty in these precise controls, the two output optical logic states may suffer from an inherent instability and a low contrast ratio of intensity. Moreover, the miniaturization of optical logic gates becomes difficult if the extra bulky apparatus for these controls is considered. As such, it is desirable to get rid of these complicated controls and to achieve full logic functionality in a compact photonic system. Such a goal remains challenging. Here, we introduce a simple yet universal design strategy, capable of using plane waves as the incident signal, to perform optical logic operations via a diffractive neural network. Physically, the incident plane wave is first spatially encoded by a specific logic operation at the input layer and further decoded through the hidden layers, namely, a compound Huygens’ metasurface. That is, the judiciously designed metasurface scatters the encoded light into one of two small designated areas at the output layer, which provides the information of output logic states. Importantly, after training of the diffractive neural network, all seven basic types of optical logic operations can be realized by the same metasurface. As a conceptual illustration, three logic operations (NOT, OR, and AND) are experimentally demonstrated at microwave frequencies. Carefully-designed diffractive metasurfaces enable accurate logical operations for optical computing. Using photons instead of electrons to convey information could reduce energy consumption and increase computing speed. However, the light properties must be controlled with very high precision in order to clearly distinguish between ‘0’ and ‘1’ logical states, and this is difficult to do without adding extra bulky components. Now, Hongsheng Chen at Zhejiang University in China and co-workers have used diffractive metasurfaces – carefully structured optical components designed from the atomic scale upwards – to realize all seven of the basic logic operations used in computation. Their components, which can be shrunk to the chip scale, clearly direct light into one of two designated areas indicating ‘0’ or ‘1’, even when the properties of the input light have not been optimally controlled.

Subfields: Artificial Intelligence, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/f23772ffe2c18bbcbe96f2641b8c56ec40898f46

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In Artificial Intelligence

  1. Yichen Shen

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