Ka Fai Chan

Abstract Orbital angular momentum (OAM) is a fundamental property of light, with widespread applications across various fields, from quantum mechanics to advanced imaging and telecommunications. The inherent orthogonality of OAM beams allows information multiplexing in unique, high-dimensional states.

1 Introduction Near-field focusing (NFF), which confines energy to a size-limited spatial region, has received an explosion of interest for its potential in short-range applications, such as radio frequency identification (RFID) systems,[1] optical imaging,[2, 3] and wireless power transfer (WPT).[4] Passive NFF designs typically concentrate on optimizing a single fixed focal point, which allows the outcome to align with the expected result closely.

1 Introduction Metalenses, which are a specialized type of metasurface, have demonstrated the ability to flexibly control the amplitude, phase and polarization of incident light beams.[1, 2] In recent years, numerous intriguing metalenses have been proposed to achieve aberration correction, diffraction-limited focusing and orbital angular momentum (OAM) generation.[3-7] To enhance the functionality of wavefront control and facilitate compact design, multifunctional metalenses have been...