Here we propose a novel broadband absorber with high efficiency by depositing nanometer iridium (Ir) film onto porous anodic alumina (PAA) template so as to increase the optical path length of the incident light for its great absorption property. Distinguished from the narrow band absorber using sub-wavelength resonant dielectric nanostructures and excitation of the propagating surface plasmon (PSP), PAA with nanometer Ir film can present broadband absorption with high efficiency as a result of the superposition of many different plasmon-enhanced absorption peaks by utilizing light funneling. The average absorption is able to achieve as high as 93.4% for 400-1100nm wavelength band and 96.8% for improved structure of quadrangular frustum pyramid array. And not only the hexagonal latticed structures of PAA template but also many similar structures based on grating or holes with square latticed or other latticed mode are able to achieve the broadband absorption with high efficiency. The absorption caused by the Ir metal layer deposited on the bottom of PAA and the funneled light into the alumina absorbed within the Ir film covering the inner sidewalls, both contribute the broadband absorption of the proposed absorber. This novel absorber can be implemented in fields of solar cell, light harvesting, imaging and so forth.
The design, fabrication and characterization of the dispersive multilayers are presented in this paper. Two kinds of
dispersive mirror (High dispersion and 700-900nm Gires-Tournois mirrors) are designed by employing Particle Swarm
Optimization method which demonstrates fast convergence speed and less dependence on the initial parameters. The
mirrors are experimentally fabricated by home-made dual ion beam sputtering system with stable deposition rate and high
density. A white light interferometry is built for precisely measuring the dispersion properties. A novel wavelet-based
differentiation approach is introduced with considerable resistance to measurement error. The good agreement between
the measured and designed results verifies the accuracy of both the fabrication and characterization method. Finally, two
applications of Yb-doped photonic crystal fiber laser and Ti:Sapphire crystal oscillation cavity, which use our fabricated
mirrors for dispersion compensation, are presented. Good output characteristics of both the two ultrafast laser systems
Due to the gradient of the phase shift as the wavelength in the reflection and transmission, the optical thin films
coatings will present the spatial dispersion effect. The new kinds of super-prism thin film devices can be realized by well
design interference effect inside of multilayer films to get the super-dispersion. The positive and negative spatial
dispersion are existed in side of coatings, and is very sensitive to the angle of incident and wavelength. The analysis
methods and the different kinds of spatial dispersion thin film filter devices and tunable spatial dispersion filter devices
are presented in the paper.
ZnO were deposited on sapphire and silicon substrates by RF magnetron sputtering from a metallic zinc target. The structural and optical propertied of ZnO films were studied by X-ray diffraction, and UV-VIS-NIR scanning spectrophotometer. XRD measurements show ZnO films had a preferential orientation along the c-axis. Only one peak, (002) phase, appears on the diffraction spectra. The transmittance spectra indicate that ZnO films possessed a transmittance of about 80% in the visible region and a sharp absorption edge at wavelength of about 390nm. The refractive index n and the extinction coefficient k are all sensitive to the oxygen partial pressure and the substrate temperature. Furthermore, based on the ideal five layers symmetrical waveguide films, the relationships of the loss and the thickness of the waveguide layer and the buffer layer were analyzed using ZnO as waveguide layer and SiO2 as buffer layer.
Graded refractive index Silicon Oxy-nitride thin films were deposited by RF magnetron reactive sputtering at different N2/O2 flow ratio. The effects of gas flow ratio on the refractive index, extinction coefficient and composition were studied using UV-VIS spectrophotometer, XPS and FTIR characterization methods. A simple and accurate method is presented for determination of the optical constants and physical thickness of thin films. Which was consisted in fitting the experimental transmission curve with the help of the physical model. The relationship between composition and optical gap and dispersion energy was analyzed using Wemple DiDomenico single-oscillator model. As a result, the samples’ refractive index can be controlled from 1.92 to 1.46 by adjusting the gas flow ratio, and the optical gap lies between 5eV~6.5eV.
The tunable optical filter used for WDM system was fabricated by employed the birefringence of liquid crystal. When the driver voltage changed, the refractive index of the liquid crystal was altered, which inverted to change the effective thickness of the cavity of the filter based on the Fabry-Perot etalon, so the peak of the transmittance was shifted and the filter achieved the tunable performance. The experiment result of the device was achieved to the tunable range from 1534.5nm to 1562.5nm and the full width of the half maximum is nearly 0.8nm and was in agreement with the design one.