Browsing by Author "Ku, Zahyun"

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    Fabry-Perot cavity resonance enabling highly polarization-sensitive double-layer gold grating
    (Springer Nature, 2018-10-03) Hwang, Jehwan; Oh, Boram; Kim, Yeongho; Silva, Sinhara; Kim, Jun Oh; Czaplewski, David A.; Ryu, Jong Eun; Kim, Eun Kyu; Urbas, Augustine; Zhou, Jiangfeng; Ku, Zahyun; Lee, Sang Jun; Mechanical and Energy Engineering, School of Engineering and Technology
    We present experimental and theoretical investigations on the polarization properties of a single- and a double-layer gold (Au) grating, serving as a wire grid polarizer. Two layers of Au gratings form a cavity that effectively modulates the transmission and reflection of linearly polarized light. Theoretical calculations based on a transfer matrix method reveals that the double-layer Au grating structure creates an optical cavity exhibiting Fabry-Perot (FP) resonance modes. As compared to a single-layer grating, the FP cavity resonance modes of the double-layer grating significantly enhance the transmission of the transverse magnetic (TM) mode, while suppressing the transmission of the transverse electric (TE) mode. As a result, the extinction ratio of TM to TE transmission for the double-layer grating structure is improved by a factor of approximately 8 in the mid-wave infrared region of 3.4-6 μm. Furthermore, excellent infrared imagery is obtained with over a 600% increase in the ratio of the TM-output voltage (Vθ = 0°) to TE-output voltage (Vθ = 90°). This double-layer Au grating structure has great potential for use in polarimetric imaging applications due to its superior ability to resolve linear polarization signatures.
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    Poly(sulfur-random-(1,3-diisopropenylbenzene)) Based Mid-Wavelength Infrared Polarizer: Optical Property Experimental and Theoretical Analysis
    (Elsevier, 2019-08) Berndt, Aaron J.; Hwang, Jehwan; Islam, Md Didarul; Sihn, Amy; Urbas, Augustine M.; Ku, Zahyun; Lee, Sang J.; Czaplewski, David A.; Dong, Mengyao; Shao, Qian; Wu, Shide; Guo, Zhanhu; Ryu, Jong E.; Mechanical and Energy Engineering, School of Engineering and Technology
    Development of polymer based mid-wavelength infrared (MWIR) optics has been limited mainly due to high optical loss of organic polymers used in general optical components. In this study, a MWIR polarization grating based on a sulfuric polymer poly(sulfur-random-(1,3-diisopropenylbenzene)) with a low loss in the MWIR range was fabricated using a simple two-step process: imprint and metal deposition. Fourier-transform infrared (FTIR) spectroscopy measurement showed that this polymeric MWIR polarizer selectively transmitted the polarized IR in transverse magnetic (TM) mode over the transverse electric (TE) mode at normal incidence. The measured extinction ratios (  = The ratio of transmissions in TM and TE) were 208, 176, and 212 at the wavelength of 3, 4, and 5 μm, respectively. The computational simulation and analytical model confirmed that the enhanced TM transmission efficiency and followed a Fabry-Pérot (FP) resonance mode within the created sulfuric polymer film. This polymeric MWIR polarizer demonstrated a great potential for broader applications in IR photonics to realize low-cost and durable optical components.