Nanowires with metallic or dielectric materials have received considerable interest in many research fields for optical and optoelectronic devices. Metal nanowires have been extensively studied due to the high optical and electrical properties and dielectric nanowires are also investigated owing to the multiple scattering of light. In this research, we report optical meta-films of alumina nanowire arrays with nanometer scale diameters by fabrication method of self-aggregate process. The aluminum oxide nanowires are transparent from ultraviolet to near infrared wavelength regions and array structures have strong diffusive light scattering. We integrate those optical properties from the material and structure, and produce efficient an optical haze meta-film which has high transparency and transmission haze at the same time. The film enhances efficiencies of optical devices by applying on complete products, such as organic solar cells and LEDs, because of an expanded optical path length and light trapping in active layers maintaining high transparency. On the other hands, the meta-film also produces solar steam by sputtering metal on the aluminum oxide nanowire arrays. The nanowire array film with metal coating exhibits ultrabroadband light absorption from ultraviolet to mid-infrared range which is caused by nanofocusing of plasmons. The meta-film efficiently produces water steam under the solar light by metal-coated alumina arrays which have high light-to-heat conversion efficiency. The design, fabrication, and evaluation of our light management platforms and their applications of the meta-films will be introduced.
We demonstrate a convenient method to improve the surface Plasmon resonance sensitivity by manipulating the
permittivity of active medium using metal-dielectric (Ag-SiO<sub>2</sub>) composite monolayer. We demonstrate the successful
permittivity engineering of SPR active medium in both theory and experiments. Based on the basic theory of SPR and
Bruggeman effective medium theory (EMT), we theoretically confirm that the angular sensitivity enhances using
manipulated permittivity of metal-dielectric composite layer.
We design the THz lens made of slit-groove-based metamaterials with tunable far-field focal length as well as
subwavelength resolution, based on surface plasmons(SP) diffraction theory into spoof SP of THz region. In THz
regime, the curved depth profile of grooves from both sides of metal slit produce directional beaming and mimic SP at
the same time. By arranging the depth of grooves in traced profile, it is possible to optimize the focal position in THz
region without changing the size of structure. It is performed numerical simulation of a designed structure through finite-difference
time-domain (FDTD) method and shows the subwavelength imaging of the designed position. In addition, the
change of focal length and the relative E<sub>x</sub> phase are observed in the simulation and help to comprehend a subwavelength
1D slit-groove-based metamaterials in THz regime.
In the manufacturing process of stainless steel, it is essential to pickle the oxide layer of steel surface for high corrosion
resistance and fine surface quality. Pickling liquor of stainless steel is commonly composed of mixed hydrofluoric and
nitric acid. Real time monitoring of concentrations of each acid is crucial to optimize pickling process. It also reduces
cost of production and decreases the generation of waste acid. We used non-contact near infrared spectroscopy
technique and rapid analysis method, for the quantification of each acid in an on-line manner. Multivariate calibration
such as partial least square regression method is employed for the better prediction results.
Mixed acid, which consist of HF and HNO<sub>3</sub>, is used as a good etchant for silicon dioxide in the wet etching and pickling
process of stainless steel. The optical detection of concentration for such mixed acids is crucial to optimize and cut costs
in the manufacturing process. Optical detection in the IR regime has been utilized to measure the concentration of the
mixed acid for HF and HNO<sub>3</sub>, because that has several strong absorption peaks, which is contributed by vibrational mode
of each acid molecular in this spectrum. In this research, we observed the concentrations of mixed acid to consist of HF
and HNO<sub>3</sub>, as we measured the absorption intensity of OH- stretch and NO<sub>3</sub>
- stretch band by optical spectroscopy. The
concentration range of HF over 1.5-3 wt% and that of HNO3 over 2-10 wt% were studied in room temperature.