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Updated: Aug 14, 2026

Characterization of Biological Absorption Spectra Spanning the Visible to the Short-Wave Infrared
Published on: January 10, 2025
Broad-band antireflection coating at near-infrared wavelengths by a breath figure
1Department of Chemical Engineering and Polymer Research Institute, Electric and Computer Engineering Division, Pohang University of Science and Technology, Kyungbuk 790-784, Korea.
Abstract:
We prepared a porous thin film by spin-coating of a cellulose acetate butyrate (CAB) solution in tetrahydrofuran under a humid environment. Due to evaporative cooling during spin-coating, condensed water droplets were formed by a breath figure on the CAB solution, and these developed a porous structure after complete drying. By varying the solution concentration and rotating speeds, two distinct morphologies were generated: top and bottom layers with higher and lower porosities, respectively. We found that the two-layer porous film coated on glass exhibited low reflectance of less than 1% in the near-infrared (NIR) regime corresponding to wavelengths between 900 and 2200 nm. Since the porous structure was very uniform over a large area, the film could be easily employed for broad-band antireflection coating at NIR wavelengths.
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