Experimentation with obliquely incident light established that all four circular reflectances of a chiral sculptured thin film backed by a metallic mirror contain strong evidence of the circular Bragg phenomenon. When the mirror is removed, strong evidence of that phenomenon is found only in the spectrum of the copolarized and cohanded reflectance.
The excitation of multiple surface-plasmon-polariton (SPP) waves and waveguide modes was experimentally demonstrated in a structure fabricated as a one-dimensional photonic crystal (PC) on top of a two-dimensional metal grating. The PC had two periods, each period comprising nine layers of silicon oxynitrides of different compositions. The individual excitations of the SPP waves and waveguide modes were also theoretically predicted using the Floquet theory, surface-multiplasmonics theory, and the transfer–matrix approach for multilayered waveguides. Both the theoretical and experimental results indicate broadband coupling of incident light of either linear polarization state to the guided waves of both types over a broad range of the angle of incidence.
Structurally chiral materials exhibit the circular Bragg phenomenon (CBP). These materials preferentially reflect
circularly polarized light of the same handedness while transmitting circularly polarized light of the opposite
handedness within a range of wavelengths called the circular Bragg regime. The CBP has been extensively
investigated experimentally for normal incidence, but not for oblique incidence. After fabricating a 20-periodthick
chiral sculptured thin film, we measured all of its circular remittances over a 60◦ range of the angle of
incidence and a 300-nm range of the free-space wavelength. Provided the incidence is not very oblique, the
obtained dependencies of the center wavelength and the bandwidth of the CBP on the angle of incidence match
theoretical estimates.
The Floquet theory and the transfer-matrix approach were used to investigate the excitation of surfaceplasmon-polariton (SPP) waves and waveguide modes in a structure comprising a one-dimensional photonic crystal (1D PC) of finite thickness on top of a planar thick metallic layer. The solutions of the relevant dispersion equations were used to predict the excitation of multiple SPP waves and waveguide modes when the metallic layer is patterned as a two-dimensional (2D) surface-relief grating. The same structure was experimentally fabricated and optically characterized to validate the theoretical approach. Both the theoretical and experimental results show broadband coupling of incident light of either linear polarization state over a broad range of the angle of incidence. This structure has potential applications in planar optical concentrators.
We excited multiple surface-plasmon-polariton (SPP) waves guided by the interface of a metal and a chiral sculptured
thin film (STF). Chiral STFs made by thermally evaporating NaF and either 3, 4, or 5 periods in thickness were
deposited on a metal film by oblique angle deposition accompanied by substrate rotation, each period being 300 nm, for plasmonic investigations in the Turbadar-Kretschmann-Raether (TKR) configuration. Reflectances were measured for a range of incidence angles for both p- and s-polarization states of the incident monochromatic light. Several reflectance minimums independent of the thickness of the chiral STF were obtained, indicating that multiple SPP waves had been excited.
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