Jang Jaewon, Park Minsu, Kang Hyeonjeong, Han Gyu-Won, Cho Hui Jae, Park Yeonsang
Departement of Physics, Chungnam National University, Daejeon, Korea.
Institute of Quantum Systems, Chungnam National University, Deajeon, Korea.
Nanophotonics. 2025 Mar 18;14(8):1291-1300. doi: 10.1515/nanoph-2024-0700. eCollection 2025 Apr.
Metasurfaces, two-dimensional planar optical devices based on subwavelength-scale structures, have garnered significant attention for their potential to replace conventional optical components in various fields. These devices can manipulate the amplitude, phase, and polarization of light in versatile ways, offering complex functionalities within a single, space-efficient device. However, enhancing their functionality remains a challenge, requiring an expansion in the design flexibility of the structural elements, known as meta-atoms. In this study, we revealed that by varying the two independent lengths of the cross-shaped structure at a wavelength of 980 nm, a phase singularity exists in the region of high reflection. In addition, we found that the phase of transmitted light can be modulated from 0 to 2 by encircling this singularity. Based on the identified phase singularity, we designed and fabricated a polarization-independent metalens with varying numerical apertures to experimentally validate the feasibility of high-reflectivity transmissive wavefront engineering metasurfaces. The introduced meta-atoms based on a phase singularity are expected to open new avenues for applications, such as those requiring light attenuation and concentration simultaneously or the development of resonant cavity structures capable of beam modulation.
超表面是基于亚波长尺度结构的二维平面光学器件，因其在各个领域替代传统光学元件的潜力而备受关注。这些器件能够以多种方式操纵光的振幅、相位和偏振，在单个紧凑的器件中提供复杂的功能。然而，增强其功能仍然是一个挑战，需要扩展被称为超原子的结构元件的设计灵活性。在本研究中，我们揭示了在980纳米波长下，通过改变十字形结构的两个独立长度，在高反射区域存在一个相位奇点。此外，我们发现通过环绕这个奇点，透射光的相位可以从0调制到2π。基于所识别的相位奇点，我们设计并制造了具有不同数值孔径的偏振无关金属透镜，以通过实验验证高反射率透射波前工程超表面的可行性。基于相位奇点引入的超原子有望为诸如同时需要光衰减和光集中的应用或能够进行光束调制的谐振腔结构的开发等开辟新的应用途径。
