Optical image addition and subtraction based on electromagnetically induced transparency effect

Abstract

The electromagnetically induced transparency (EIT) effect is a quantum coherence effect between different atomic transition channels. The absorption of the atomic ensemble is significantly reduced or even close to zero, and at the same time, this effect is accompanied by strong spectral dispersion near the resonant frequency of atoms, which is widely used in group velocity control, light pulse storage, and coherent manipulation on the light field. In the light pulse storage based on the EIT effect, the retrieval field is determined by the signal, coupling, and readout fields, enabling the retrieval field to be dynamically controlled by manipulating the spatial frequency components of the interacting light fields. In this paper, according to the EIT effect, we achieve experimentally the optical image addition and subtraction in the imaging plane of a 4<inline-formula><tex-math id="M2">\begin{document}$f$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20221560_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20221560_M2.png"/></alternatives></inline-formula> system through the coherent manipulation of the retrieval field via the interacting signal, coupling, and readout fields. Specifically, we first store the spatial frequency spectrum of a double-slit mask in the praseodymium-doped yttrium silicate crystal located in the confocal plane of the 4<inline-formula><tex-math id="M3">\begin{document}$f$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20221560_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20221560_M3.png"/></alternatives></inline-formula> system based on the EIT effect. Then, we utilize a specially designed mask containing the target objects and perform spatial filtering by using the spatial frequency spectrum of the double-slit mask through the retrieval of stored light pulse. By moving the double-slit mask, the addition and subtraction between the images of target objects can be achieved in the imaging plane of the 4<inline-formula><tex-math id="M4">\begin{document}$f$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20221560_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20221560_M4.png"/></alternatives></inline-formula> system. We present a theoretical model to describe the addition and subtraction between the target images through the EIT-based light pulse storage technique. The experimental results accord well with the theoretical prediction. Compared with the traditional scheme with a cosine grating filtering the spatial frequency spectrum, our method does not require the preparation of a spatial frequency filter, and only produces the first-order positive and negative diffraction images without the influence of the zeroth-order diffraction image. The optical image addition and subtraction based on the EIT effect provide a new approach to optical image processing. This approach is not limited to image addition or subtraction, and it can be extended to achieve more complex operations such as differentiation, enhancement, encryption, and decryption with rational design. Therefore, it can be widely used in areas such as coherent manipulation of light fields and dynamic optical image processing.