Silicon Micro/NanoPhotonics Group, Carleton University, Ottawa, ON K1S 5B6, Canada.
Sensors (Basel). 2023 Apr 20;23(8):4137. doi: 10.3390/s23084137.
Metalenses are planar optical components that have demonstrated immense potential for integrated optics. In particular, they are capable of high-efficiency subwavelength focusing without the bulkiness of traditional lenses. Dielectric metalenses operating in the C-band typically employ relatively tall, amorphous silicon structures arranged in a periodic array. Phase control spanning from 0 to 2π is accessed by varying the geometry of these scattering structures. The full 2π phase range is necessary to impose a hyperbolic focusing phase profile, but this is difficult to achieve without custom fabrication practices. In this work, we propose a binary phase Fresnel zone plate metalens designed for the standard 500 nm silicon-on-insulator platform. Our design uses subwavelength gratings with trapezoidal segmentation to form concentric rings. The effective index of the grating is set with the duty cycle using a single full-etch step to form the binary phase profile of the zone plate. The metalens design can be easily tuned to achieve longer focal lengths at different wavelengths. It offers a simple platform for high-throughput wavelength-scale focusing elements in free-space optics, including for microscopy and medical imaging.
超构透镜是一种平面光学元件，在集成光学领域具有巨大的应用潜力。特别是，它们能够在不使用传统透镜的情况下实现高效的亚波长聚焦。在 C 波段工作的介电超构透镜通常采用相对较高的非晶态硅结构，这些结构排列在周期性的阵列中。通过改变这些散射结构的几何形状，可以实现从 0 到 2π 的相位控制。要施加双曲聚焦相位分布，需要全 2π 相位范围，但如果没有定制的制造工艺，这很难实现。在这项工作中，我们提出了一种用于标准 500nm 硅衬底上的二进制相位菲涅耳波带片超构透镜。我们的设计使用具有梯形分段的亚波长光栅形成同心环。通过使用单个全刻蚀步骤来设置光栅的有效折射率和占空比，从而形成菲涅耳波带片的二进制相位分布。该超构透镜设计可以轻松地进行调整，以在不同波长下实现更长的焦距。它为自由空间光学中的高吞吐量波长级聚焦元件提供了一个简单的平台，包括显微镜和医学成像。
