研究目的
To demonstrate a miniature aberration-corrected spectrometer with nanometer spectral resolution across the visible spectrum using a single planar off-axis focusing metalens.
研究成果
The study demonstrates an aberration-corrected off-axis metalens that enables a highly compact spectrometer with nanometer resolution across 200 nm in the visible spectrum. This approach can correct for chromatically induced astigmatism and field curvature in metalens spectrometers and essentially engineer the focal length to be an arbitrary function of frequency.
研究不足
The efficiency of the metalens is generally low (<15%), partly due to the lack of degrees of freedom in the coupled nano-fin elements to independently optimize for efficiency. Additionally, the metalens works only for one helicity of circularly polarized light, limiting its application in scenarios requiring polarization insensitivity.
1：Experimental Design and Method Selection
The study employs a single planar off-axis focusing metalens consisting of subwavelength TiO2 nanofins. The design involves dispersion engineering to tailor the phase, group delay (GD), and GD dispersion of the metalens.
2：Sample Selection and Data Sources
The metalens was fabricated via electron-beam lithography and atomic layer deposition of titanium oxide. Its performance was characterized using a collimated supercontinuum laser source and a CMOS camera.
3：List of Experimental Equipment and Materials
Electron-beam lithography system, atomic layer deposition system, collimated supercontinuum laser source (SuperK Varia, NKT Photonics), CMOS camera (Thorlabs DCC 1545M).
4：Experimental Procedures and Operational Workflow
The metalens was illuminated with collimated monochromatic laser light at various wavelengths, and the resulting focal spots were captured with a CMOS camera. The dispersion and efficiency of the metalens were measured across the visible spectrum.
5：Data Analysis Methods
The spectral resolution was calculated based on the focal spot size and the reciprocal linear dispersion. The efficiency was defined as the power contained in the focal spot normalized to the incident power.
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