Design of broadband achromatic far-infrared metalens based on chalcogenide glass using parameterized topology optimization
doi: 10.37188/CO.EN-2025-0003
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摘要:
超透镜技术在小型化、集成化红外成像系统中有着广泛的应用。然而，由于单元结构的色散较高，导致超透镜经常出现色差，使得宽带消色差红外成像难以实现。该文章构建了基于硫系玻璃的6种不同单元结构，并对其相位色散参数进行分析，建立数据库。在此基础上，采用色差补偿和参数化伴随拓扑优化的方法，在远红外波段将这6种单元结构排列组合，设计出数值孔径为0.5的宽带消色差超透镜。仿真结果表明，该超透镜在9~11µm的工作波长范围内实现了近衍射极限聚焦，具有良好的消色差性能，全波长具有为54%~58%的平坦的聚焦效率。
Abstract:Metalens technology has been applied extensively in miniaturized and integrated infrared imaging systems. However, due to the high phase dispersion of unit structures, metalens often exhibits chromatic aberration, making broadband achromatic infrared imaging challenging to achieve. In this paper, six different unit structures based on chalcogenide glass are constructed, and their phase-dispersion parameters are analyzed to establish a database. On this basis, using chromatic aberration compensation and parameterized adjoint topology optimization, a broadband achromatic metalens with a numerical aperture of 0.5 is designed by arranging these six unit structures in the far-infrared band. Simulation results show that the metalens achieves near diffraction-limited focusing within the operating wavelength range of 9−11 µm, demonstrating the good performance of achromatic aberration with flat focusing efficiency of 54%−58% across all wavelengths.
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Key words:
- metalens /
- chalcogenide glass /
- topology optimization /
- high efficiency /
- long wave infrared /
- broadband operation
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Figure 1. (a) Schematic for achromatic metalens. (b) Schematic for phase profile of an achromatic metalens
Figure 3. (a) Phase simulation results of unit structure. (b) Distributions of the phase-dispersion parameters for the solid square column structure, where red cross and blue point represent the phase-dispersion parameters of an actual square column structure and the theoretical structure, respectively. (c) Database of the phase-dispersion parameters for all unit structures. (d) Distributions of the phase-dispersion parameters of the initial structure closest to theoretical structures for each position
Figure 6. (a) Schematic diagram of the unit structures changes. (b) The normalized phase distribution of the metalens after the iteration step of 0 and 40. (c) Variation of focusing efficiency corresponding to different incident wavelengths concerning the step of optimization iterations
Figure 7. (a) Distribution of normalized light intensity on the x-z plane, with the white dashed line indicating the position at 180 µm. (b) Distribution of normalized light intensity at the focal point on the x-y plane
Figure 8. (a) Focal lengths at different wavelengths. (b) FWHM values at different wavelengths, and corresponding FWHM values that meet the diffraction limit
Figure 10. (a) The original image. (b) The simulated image in the wavelength range of 9−11 µm
Table 1. Summary of performances for broadband achromatic metalens
NA Operating wavelength/µm Diameter/µm Average focusing efficiency Polarization Ref. 0.6 0.45−0.75 6 45% Insensitive [11] 0.6 0.63 20 65% Circular [10] 0.11 0.62 112 45% Circular [24] 0.38 3−5 30 46.5% Insensitive [8] 0.56 0.64 10.2 50% Circular [25] 0.82 15.5 50 72% Circular [26] 0.54 8.6−11.4 191.4 38.2% Circular [27] 0.5 9−11 204 56% (54%−58%) Insensitive This paper 
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