Design and fabrication of a 100mm-diameter pillar metalens for high performance mid-infrared imaging

Jin, Weilin, Dong, Gaochen, Wang, Zixuan, Kiang, Kian and Yan, Jize (2025) Design and fabrication of a 100mm-diameter pillar metalens for high performance mid-infrared imaging. 51st International Micro and Nano Engineering Conference, National Oceanography Centre, Southampton, United Kingdom. 15 - 18 Sep 2025.

Abstract

As a new class of flat optical devices with submillimeter thickness [1], metalenses enable simultaneous control of light's amplitude, phase, and polarization through precisely designed subwavelength nanostructures. In astronomy and environmental monitoring, increasing lens diameter typically leads to substantial growth in volume and weight [2]. Thinner metalenses, with their ultracompact form factor, offer a lightweight, space saving alternative to bulky traditional optics. However, most high-performance metalenses are limited to millimeter-scale diameters due to data storage and fabrication constraints in defining billions of nanostructures[3]. Although Park et al. demonstrated the feasibility of fabricating a 100 mm-diameter visible metalens using
stitched DUV lithography, limitations remain from nonuniform feature fidelity across stitched fields [1]. Thus, developing a method that reduces data volume and ensures consistent pattern quality across the full aperture is essential for efficient layout handling and improved nanostructure definition.
For our 100mm-diameter metalens, the design includes 4.9 × 108 silicon nanopillars. Conventional methods for generating this size layout would require hours to days and consume approximately 12.5 GB of disk space [3]. Processing such large files at high resolution presents significant challenges for electron-beam lithography(EBL). To address this issue, we implemented a parallel strategy to reduce both the running time and file size. This approach involves dividing the layout into multiple sub-layouts of equal area and assigning them to different computing nodes for parallel generation separately and aggregation. Using this method, we generated the layout within 5 minutes and reduced full file size from 64GB to 293MB in OASIS format. This strategy not only accelerates pattern generation but also reduces data handling overhead during the EBL writing process.
We fabricated mid-infrared metalens with a 100 mm diameter and a thickness of 0.725 mm, achieving NA~0.25 focusing at a wavelength of 10 μm through CMOS-compatible processes. The fabrication workflow(Fig.1) involved uniform hard mask deposition, precision electron-beam lithography with calibrated exposure dose and beam current for pattern uniformity across the full wafer, 80 °C-controlled lift-off, and deep reactive ion etching (DRIE). The DRIE process was iteratively optimized by tuning temperature,
etching duration, and RF power, yielding vertical sidewalls with angles exceeding 89°. Structural fidelity was monitored using optical microscopy, ellipsometry, and SEM. As shown in Fig. 2a and 2b, the metalens consists of a uniform array of silicon nanopillars arranged in a 4 µm-period. Due to varying gap sizes between pillars, the etch depths range from 5 to 6 µm. This geometry enables full 0–2π phase modulation(Fig. 2d).
The imaging experimental setup and results are shown in Fig. 3. The metalens is integrated as the first element in a standard 4f imaging system, where two lenses are placed at a distance equal to the sum of their focal lengths (Fig.3a). In this configuration, the metalens collects and collimates infrared light from a distant object, which is then refocused by a secondary lens onto a thermal camera sensor at the image plane. Using this system, we captured mid-infrared images of a human finger and retrieved accurate temperature distribution. This represents the first demonstration of a 100 mm-class metalens operating at a 10 μm wavelength, marking an important step toward scalable, wafer-level metasurface optics for infrared imaging and sensing applications.

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Contributors

Author: Weilin Jin

Author: Jize Yan

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