Subwavelength imaging using orbital angular momentum waves generated by metasurfaces.

Using conventional imaging techniques, the maximum obtainable resolution of an object is limited to about half the wavelength of the incident light, a phenomenon known as the diffraction limit. This limitation poses significant challenges in fields requiring high-resolution imaging, such as microscopy and nanotechnology. In this paper, we address this challenge by designing a dielectric metasurface to generate an optical Laguerre-Gaussian (LG) orbital angular momentum (OAM) beam. This innovative approach leverages the unique properties of OAM beams to achieve imaging beyond the diffraction limit. The dielectric metasurface is meticulously engineered to control both the phase and amplitude of the output wave, enabling the generation of high-quality LG OAM beams. Unlike traditional near-field and far-field imaging techniques, our proposed method does not necessitate a restricted distance between the imaging system components, offering greater flexibility and practicality in various applications. To validate the performance of our method, we conducted comprehensive numerical simulations. The results demonstrate that the generated OAM beam can achieve a resolution of 0.29 times the incident wavelength, surpassing the conventional diffraction limit.