Yi-Jun Jen

Multiple trains of same-color surface plasmon-polaritons guided by the planar interface of a metal and a sculptured nematic thin film. Part III: Experimental evidence

The absorbance, reflectance, and transmittance of a linearly polarized, obliquely incident plane wave were calculated for the planar interface of a metal and a sculptured nematic thin film (SNTF) in the Kretschmann configuration, the wave vector of that plane wave being arbitrarily oriented with respect to the morphologically significant plane of the SNTF. The permittivity profile of the chosen SNTF was supposed to have been sculptured during physical vapor deposition by varying the vapor incidence angle sinusoidally about a mean value. Regardless of the orientation of the wave vector, multiple surface-plasmon-polariton (SPP) trains or waves of the same color but different phase speeds and guided by the metal/SNTF interface can be excited.

Vapor-deposited thin films with negative real refractive index in the visible regime

A thin film comprising parallel tilted nanorods was deposited by directing silver vapor obliquely towards a plane substrate. The reflection and transmission coefficients of the thin film were measured at three wavelengths in the visible regime for normal-illumination conditions, using ellipsometry and walk-off interferometry. The thin film was found to display a negative real refractive index. Since vapor deposition is a well-established industrial technique to deposit thin films, this finding is promising for large-scale production of negatively refracting metamaterials.

Multilayered structures for p- and s-polarized long-range surface-plasmon-polariton propagation

A normalized admittance diagram assists in describing and designing multilayered structures to excite long-range surface-plasmon-polariton (LRSPP) waves of either the p- or the s-polarization state. These structures comprise symmetric periodic multilayers on one or both sides of a metal thin film in either the Kretschmann or the Sarid configuration. The normalized admittance diagram even assists in designing structures that can be used to excite LRSPP waves of both polarization states simultaneously.

Optical constant determination of an anisotropic thin film via polarization conversion

This study presents a simple method for determining the optical constants of an anisotropic thin film. The sensitivity of enhanced polarization conversion reflectance to optical constants is also calculated and analyzed. Based on the sensitivity calculation, the principal indices and columnar tilt angle can be derived from the polarization conversion reflectance angular spectrum.

Biologically inspired achromatic waveplates for visible light

Waveplates are planar devices used in optics and optoelectronics to change the polarization state of light. Made of anisotropic dielectric materials such as crystals and thin films, waveplates are not known to exhibit achromatic performance over the visible regime. Inspired by the microvillar structure of R8 cells functioning as polarization converters in the eyes of stomatopod crustaceans, we conceived, designed, fabricated and tested periodically multilayered structures comprising two different types of arrays of nanorods. Morphologically analogous to the ocular cells, here we show that the periodically multilayered structures can function as achromatic waveplates over the visible regime.

Giant optical anisotropy of oblique-aligned ZnO nanowire arrays

A combined method of modified oblique-angle deposition and hydrothermal growth was adopted to grow an optically anisotropic nanomaterial based on single crystalline ZnO nanowire arrays (NWAs) with highly oblique angles (75°-85°), exhibiting giant in-plane birefringence and optical polarization degree in emission. The in-plane birefringence of oblique-aligned ZnO NWAs is almost one order of magnitude higher than that of natural quartz. The strong optical anisotropy in emission due to the optical confinement was observed. The oblique-aligned NWAs not only allow important technological applications in passive photonic components but also benefit the development of the optoelectronic devices in polarized light sensing and emission.

Deposited metamaterial thin film with negative refractive index and permeability in the visible regime.

Thin films are fabricated from arrays of silver nanorods with thicknesses of 160 nm and 200 nm, to function as a metamaterial. The negative refractive index and negative permeability are retrieved from measured reflection and transmission coefficients using walk-off interferometer in the visible regime. A negative-index-material thin film with negative permittivity or (and) permeability can be produced by glancing angle deposition.

Anisotropic optical thin films finely sculptured by substrate sweep technology

In this paper, we have fabricated for the first time films with different orientations of principal axes but similar principal indices and also films with different principal refractive indices but the same orientations of principal axes. During deposition, the deposition angle and the substrate sweep angle are varied to control separately the porosity (refractive principal indices) and column tilt angle (orientations of principal axes) of a birefringent thin film.

Metal/dielectric/metal sandwich film for broadband reflection reduction.

A film comprising randomly distributed metal/dielectric/metal sandwich nanopillars with a distribution of cross-sectional diameters, displayed extremely low reflectance over the blue-to-red regime, when coated on glass and illuminated normally. When it is illuminated by normally incident light, this sandwich film (SWF) has a low extinction coefficient, its phase thickness is close to a negative wavelength in the blue-to-red spectral regime, and it provides weakly dispersive forward and backward impedances, so that reflected waves from the two faces of the SWF interfere destructively. Broadband reflection-reduction, over a wide range of incidence angles and regardless of the polarization state of the incident light, was observed when the SWF was deposited on polished silicon.

Surface plasmon resonance via polarization conversion in a weak anisotropic thin film

A columnar structured thin film with weak anisotropy is applied to trigger the electromagnetic wave with forbidden polarization state to excite surface plasmon. The precursory work is done here for the conventional Kretschmann configuration [D. Sarid, Phys. Rev. Lett. 47, 1927 (1981)] by arranging an anisotropic thin film in the configuration as a three-layered system (prism/anisotropic dielectric film/metal film/isotropic thin film/air). It enables both p-polarized and s-polarized incident waves simultaneously to excite surface plasmon.