In this work, TiN uniform thin films and nanostructured thin films were fabricated in a magnetron sputtering system. Two sets of TiN thin films with and without substrate bias were deposited at a nitrogen flow rate varied from 1.2 sccm to 2.0 sccm. The permittivity spectra of TiN films were measured and compared between different deposition conditions. A glancing angle-deposited TiN nanorod array was deposited with substrate bias. The polarization dependent extinction versus wavelength and angle of incidence was measured to discuss the associated transverse and longitudinal plasmonic modes.
Three-dimensional chiral metamaterials, plasmonic nanohelixes, with chiroptical activity have attracted attention for many potential photonic applications. In previous works, glancing angle deposition (GLAD) has been applied to deposit various Ag nanohelix arrays on smooth substrates and the structure dependent circular dichroism has been measured and analyzed. In this work, two-turn SiO<sub>2</sub> nanohelixes are grown upon Ag nanohelixes to form a SiO<sub>2</sub>-Ag nanohelix array. For the bottom Ag nanohelices, the average pitch length (P) and the radii of curvature (R) are 231nm and 137nm, respectively. P and R are 174nm and 118nm for the top SiO<sub>2</sub> nanohelices, respectively. Under left-handed (righthanded) circularly polarized light illumination, the transmittance, reflectance, and extinctance of the SiO<sub>2</sub>-Ag nanohelix array are measured. The circular dichroism described with g-factor is also presented here as a function of wavelength. According to the measurement, the g-factor exhibits a shift phenomenon as the SiO<sub>2</sub> nanohelixes are capped upon Ag nanohelixes. This phenomenon leads to flexible control over the circular dichroism of SiO<sub>2</sub>-Ag nanohelix arrays with respect to the resonance wavelength and amplitude of g-factor.
A traditional high-reflection optical coating was applied to enhance the directional radiation of nanoantennas. A highly reflective multilayer upon the top lateral side of a horizontally lying silver nanorod enhances the forward scattering when an optical wave is incident on the bare bottom side of the nanorod. Enhanced forward scattering can thus be observed from a glancing deposited silver nanorod array (NRA). An effective method for coupling the energy of incident light into a NRA involves arranging the NRA in a prism coupling. The highly efficient light coupling effect over a broadband and a wide range of angles results in extra-strong forward light scattering.
A slanted silver nanorod array (NRA) deposited with glancing angle of deposition around 89°. By controlling the
deposition angle, SiO2 and Ta2O5 grow on sliver rods in different morphologies. The multilayer designed as high
reflective multilayer by arranging SiO2 and Ta2O5 alternatively on a cylindrical silver rod with diameter of 80 nm and a
length of 200 nm would enhance the local field intensity and scattering when the rod is illuminated by s-polarized and ppolarized
light waves. In this work, the reflective multilayer is designed at wavelengths of 450nm and 750nm that are
associated with transverse plasmonic mode and longitudinal plasmonic mode, respectively. It is demonstrated
experimentally that the intensity of light scattering from the capped NRA is enhanced due to the local field confinement
around silver rod.
Three aluminum (Al)/silicon dioxide (SiO 2 )/aluminum (Al) nanosandwich films (SWFs) of various heights were fabricated using glancing angle deposition. An SWF comprises a 45-nm thick SiO 2 layer sandwiched between two Al nanopillars. The thicknesses of both top and bottom nanopillars were varied from 187.5 to 217.5 nm. The equivalent constitutive and related parameters of each SWF were obtained from the reflection coefficients and transmission coefficients that were measured using a walk-off interferometer. Both the equivalent permittivity and the equivalent permeability of each SWF turned out to be negative real. Exactly how the height of the Al nanopillars of the double negative SWF affects its low reflectance through destructive interference is also examined using the wave tracing method. Moreover, the localized reversed magnetic field in the SiO 2 layer of each SWF was simulated by finite-difference time-domain method to qualitatively interpret the negative real permeability.
In this work, three different aluminum (Al) / silicon-dioxide (SiO<sub>2</sub>) / aluminum (Al) nanosandwich films (SWFs) with different sizes are deposited using glancing angle deposition (GLAD) with continuous azimuthal rotation. The SWF comprises an SiO<sub>2</sub> layer that is sandwiched between Al nanopillars. The thickness of SiO<sub>2</sub> is fixed at 45nm. The thicknesses <i>d</i> of the top and bottom Al nanopillar is varied from 188nm to 233nm. The equivalent electromagnetic parameters of each film are derived from the reflection coefficients and transmission coefficients that are measured by walk-off and polarization interferometers. The equivalent optical parameters revealed that it has a negative real equivalent permittivity and a negative real equivalent permeability. The effect of size of the Al / SiO<sub>2</sub> / Al SWFs on their optical properties is also examined. As the thickness <i>d</i> increases from 188nm to 233nm, the equivalent refractive index is negative and its average magnitude decreases from -1.703 to -1.247. Similarly, the real part of the equivalent permittivity varies from -1.193 to -0.824 as the thickness increased. The SWFs are simulated to analyze the magnetic field in the SiO2 layer by finite-difference time-domain (FDTD) method. The result of the simulation shows that the negative permeability arises from the reversal of the magnetic resonance within the SiO2 layer. The reversed magnetic field becomes weaker as the thickness <i>d</i> increases.
The equivalent electromagnetic parameters of a three-layered system Air/ Ta<sub>2</sub>O<sub>5</sub> NRA (165nm)/ SiO<sub>2</sub> NRA (133nm)/ Ag NRA(130nm) /BK7, fabricated by glancing angle deposition, are derived. The equivalent optical constants are used to estimate the optical performance that is achieved when additional films are deposited upon the NRA. First, the Ag NRA is deposited at a deposition angle of 89deg. An SiO<sub>2</sub> NRA is then deposited at a deposition angle of -89deg. Finally a Ta<sub>2</sub>O<sub>5</sub> NRA is deposited upon the SiO<sub>2</sub> NRA at a deposition angle of 80deg. The reflectance and transmittance of the three-layered system Air/ Ta<sub>2</sub>O<sub>5</sub> NRA (165nm)/ SiO<sub>2</sub> NRA (133nm)/ Ag NRA(130nm) /BK7 glass are measured and compared with the theoretically estimated reflectance. At a wavelength of 568nm, the theoretically estimated p-polarization reflectance is 21.75%, which is close to the measured reflectance of 20.3%. A suitable arrangement of dielectric thin films upon a metamaterial thin film is demonstrated to induce p-polarized transmission.
We propose a design method of an achromatic waveplate that comprises anisotropic thin films as a multi-cell layered system. Each cell is a symmetrical three-layered ABA structure with equivalent refractive indices and phase thicknesses. A merit function defined as the rate of change of the phase retardation with respect to wavelength is introduced to control the variation of phase retardation by selecting proper birefringence and thickness for each film. The allowed thickness of each birefringent film is investigated for different requirement about the uniformity of phase retardation. An achromatic waveplate with a smaller number of cells is demonstrated by arranging the two composed films made of different materials with high contrast of refractive index between them. The arrangement of a matching layer, which is associated with the performance of the achromatic waveplate, is also discussed.
This work presents a wide angle phase retarder by using a single anisotropic Ta<sub>2</sub>O<sub>5</sub> columnar thin film. The single
anisotropic Ta<sub>2</sub>O<sub>5</sub> columnar thin film can provide phase retardation between two tangential eigenvectors to modulate
the polarization state of light reflected from the prism-coupling system (BK7 prism/anisotropic thin film/air). In
experiment, glancing angle deposition technique is used to prepare single layer film of Ta<sub>2</sub>O<sub>5</sub> tilted nanorod array with
thickness 270nm. In this analysis, we use wave tracing based on the Berreman calculus to calculate the variations of
phases of eigen-waves in the anisotropic thin film as the electromagnetic wave is incident to the prism-coupling system.
The uniform phase retardation can be observed in a wide angle range. A linearly polarized incident ray can be reflected
as a specific elliptical polarized ray uniformly over the range. Similarly, the wide angle and broadband polarization
conversion reflectance with high efficiency also exists in the single anisotropic Ta<sub>2</sub>O<sub>5</sub> columnar thin film. The single
anisotropic Ta<sub>2</sub>O<sub>5</sub> columnar thin film can be useful for the further application in optical components design.
In this work, the birefringence of bideposited symmetric nanorod array is investigated. The Ta<sub>2</sub>O<sub>5</sub> nanorod arrays
composed of several subdeposits are fabricated by serial bideposition (SBD) technique. Each nanorod consists of several
identical units and each unit consists of symmetrical sections ABA. From the lateral view of the structure, the nanorod
array is a symmetrical multilayered. The deposition planes for layer A and layer B are perpendicular to each other. For
normal incident ray, the polarization-dependent refractive indices and phase thicknesses of the film are presented as
functions of wavelength and optical constants of each layer. The transmittance spectra of symmetrical sections have a
pass band property as the equivalent refractive indices are real. The principal indices of the Ta<sub>2</sub>O<sub>5</sub> nanorod arrays with
each subideposition thickness of 3 nm associated with the two orthogonal polarizations are measured by ellipsometer
when the deposition angle is changed from 70° to 80°. According to principal indices database, a uniform phase
retardation between the two orthogonal polarization directions can be designed for a specific wavelength range.
This work presents a three-layered thin film system to generate broadband polarization conversion. The enhanced polarization conversion in the prism coupling system is analyzed as a constructive interference effect of polarization coupled states. According to our analysis, an antireflection film that is used to reduce the multireflection in the anisotropic film and a compensation film that is used to reduce dispersion of propagation phase difference are applied on both sides of an anisotropic thin film to cause broadband polarization conversion.
In this work, a simple and high efficient way to change the polarization state is proposed. A broadband polarization
conversion (PC) filter based on a prism coupling system (BK7 prism/anisotropic film/air) is investigated. The anisotropic
SiO<sub>2</sub> thin film prepared by glancing angle deposition is a columnar thin film with near uniaxial property. At a certain
angle range around 51.5. over the critical angle, there exists an enhanced PC reflection when the plane of incidence is
vertical to the deposition plane. The reason of polarization conversion (PC) reflectance in an anisotropic SiO<sub>2</sub> thin film
(n1', n2', n3') = (1.260, 1.216, 1.215) is analyzed and interpreted in the prism-coupling system (prism/ SiO<sub>2</sub> thin film
/air). In order to achieve the broadband PC reflectance spectrum, a three-layered structure (isotropic MgF<sub>2</sub> thin film/
anisotropic SiO<sub>2</sub> thin film/ isotropic MgF<sub>2</sub> thin film) was arranged. The three-layered structure thin film is investigated
optimum ability as broadband polarization device.