Liquid Crystal Integrated Metalens for Versatile Color Focus
Arthur T Knackerbracket has found the following story:
Among metadevices, the metalens has attracted widespread attention for practical applications in imaging and spectroscopy, as it provides multifunctional wavefront manipulations for improved focus.
Metalenses are plagued by failure to focus all colors to the same point, which is known as chromatic aberration. Overcoming chromatic aberration is a vital concern for improved resolution in full-color and hyperspectral imaging. On the contrary, for spectrographic analysis and tomographic applications, chromatic dispersion helps to separate focal spots for different frequencies to avoid crosstalk.
[...] A research team from Nanjing University recently demonstrated active manipulation of chromatic dispersion, achieving achromatic focusing within a designated broadband. As reported in the peer-reviewed, open-access journal Advanced Photonics, the team integrated a photo-patterned liquid crystal into a dielectric metasurface. In their design, the metasurface generates a linear-resonant phase dispersion, which means that the phase front of the transmitted wave is delayed linearly by the dielectric metasurface. The liquid crystal (LC) is responsible for generating frequency-independent geometric phase modulation.
The team verified the chromatic aberration control of the combined lens and demonstrated a significant dynamic broadband imaging contrast effect. The design can be extended to other active metadevices; as an example, the team presented a beam deflector with controllable dispersion. "Combining the flexibility of metadevices with the broadband electro-optical characteristics of liquid crystals makes the design competent for wavefront control from the visible wavelengths to the THz and microwaves," remarked senior author Prof. Yanqing Lu, of the College of Engineering and Applied Sciences at Nanjing University.
Journal Reference:
Zhixiong Shen, Shenghang Zhou, Xinan Li, et al. Liquid crystal integrated metalens with tunable chromatic aberration [open], Advanced Photonics (DOI: 10.1117/1.AP.2.3.036002)
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