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The optical properties of amorphous PbZr0.52Ti0.48O3 thin films on vitreous silica and sapphire substrates by the RF magnetron sputtering method have been investigated by transmittance measurements. For a single-layer thin film on the transparent substrate, the inverse synthesis or fitting method with the six fitting parameters was given and used to calculate the optical constants such as the refractive index n, the extinction coefficient k, and the absorption coefficient α. The film thickness d, which was one of the fitting parameters, is simultaneously obtained. According to Tauc''s law, the optical transition in amorphous PbZr0.52Ti0.48O3 thin films is direct in nature. The direct band gaps of amorphous PbZr0.52Ti0.48O3 thin films on vitreous silica and sapphire substrates were found to be 3.36 and 3.25 eV, respectively. The dispersions of the refractive index in films were studied by considering a single-oscillator model. [Copyright &y& Elsevier]

Here we report that a simple chiral metasurface with twisted metallic cut-wire arrays enables highly efficient and continuously tunable chiral absorption over a broad spectral range by scanning the incidence angle over a few degrees. The angle-selective chiral absorption results from the surface plasmon resonance (SPR) excited by diffractive effects of the metasurface. The diffraction-assisted chiral metasurface provides a straightforward strategy for achieving dynamically tunable chiral devices and offers intriguing possibilities for various applications in on-chip chiral detectors/emitters, chiral spectrometers, chiral lasers, and so on.

Spin-selective absorption in a two-dimensional (2D) chiral plasmonic grating is observed by excitation of chiral-dependent plasmonic cavity resonance. For the proposed structures, the incident right-handed circularly polarized light is absorbed with nearly 100% efficiency, whereas the incident left-handed circularly polarized light is reflected with same handedness. Moreover, we show that the location of spin-selective absorption can be controlled flexibly by tuning the plasmonic cavity dimension. The intensity of spin-selective absorption can be enhanced as well as suppressed based on Fabry-Perot interference phase relation. Such 2D chiral plasmonic gratings could find many potential applications in novel photon-spin selective devices, such as circularly polarized light detectors/emitters, chiral sensors, chiral cavities, and spin lasers.

Spectral responses in compound waveguide grating structures composed of two ridges with identical widths in each period are presented. For the proposed structures, we show that the spectral width of the guided-mode resonance (GMR) can be tailored in an independent way without modifying the spectral lineshapes and sideband levels. The method described in this Letter offers a very simple and efficient way to control spectral responses in GMR structures.

We report that a narrow guided-mode resonance (GMR) filter with high-index substrate can be achieved by introducing an added layer on the substrate. For this type of GMR filter, the refractive index and thickness of the added layer are the critical parameters for the GMR effect to occur. We demonstrate that this filter has good fabrication tolerances for the grating thickness and fill factor. Our design may promote the application of GMR filters in practice.

A shallow grating triple-layer guided-mode resonance (GMR) filter and its properties are presented. For this type of GMR filter, the grating layer has the equal refractive index to the waveguide layer. It is shown that the GMR filter with shallow grating has good characteristics of narrow bandwidth, symmetrical line shape, and low-reflection sideband. The spectral FWHM of the GMR filter can be controlled by varying the grating thickness. The desired FWHM at the same resonance wavelength with symmetrical line shape and low-reflection sideband can be obtained by adjusting the grating thickness and the grating period with the total thickness of the grating and waveguide layers kept unchanged.