Abstract: The transmission properties of electromagnetic wave (EMW) can be modulated by the periodic structure of photonic crystal (PhC) to bring many novel optical effects. The special distributions of equal frequency contours (EFCs) can be used to control the wavefront state and transmission direction of propagating wave in PhC with some special effects, such as non-handed refraction. Based on the intricate undulation of one single band or the overlap of different bands, the phenomena of dual-negative refraction, symmetrical positive-negative refraction and triple refraction have been achieved in the higher band regions. These unique features will provide us with more understanding of electromagnetic wave propagation in PhCs and give important guideline for the design of new type optical devices.
Abstract: SnS2/SnO2 nanocomposite was synthesized by a simple in situ hydrothermal oxidation route, and characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy and UV-vis diffuse reflectance spectrum. The as-synthesized SnS2/SnO2 nanocomposite displayed much superior photocatalytic activity to SnS2 and SnO2 nanoparticles in the reduction of aqueous Cr(VI) under visible light (λ > 420 nm) irradiation.
Abstract: Raman, resonant Raman and photoluminescence (PL) properties of ZnO nanorods that produced by simple solution chemical process are reported in this paper. The transmission electron microscopy measurements show that the obtained ZnO nanorods have well-proportioned distribution with diameters about 30 nm, and the maximal lengths up to more than 2.2 μm. The micro-Raman and resonant Raman spectrum of nanorods show the obvious differences from that of the commercial bulk phase ZnO samples. The PL with intense UV emission indicates the good quality of the obtained ZnO nanorods.
Abstract: In this thesis, ZnO nanostructures with different morphologies were synthesized on silicon substrates by chemical solution growth method from Zinc acetate and methenamine aqueous solution at 70°C for 4 hours. Its morphologies by SEM and its crystal structures by XRD were studied．Its photoluminescence spectrum was also measured．And possible mechanisms of the growth and the photoluminescence of ZnO were proposed to explain the experimental result．
Abstract: Trivalent Eu and Dy ions co-doped amorphous strontium aluminate oxide (SrAl2O4:Eu3+Dy3+) were synthesized through solution combustion route. The phase of the synthesized compound was examined with the X-ray diffractometry. The photoluminescence spectra of the amorphous SrAl2O4:Eu3+Dy3+ has shown that the sharp blue emission of Dy3+ at 483 nm, the sharp yellow emission of Dy3+ at 570 nm and the sharp red emission of Eu3+ at 615 nm can be integrated into the broad blue background emission of the amorphous host. The results indicate that the amorphous SrAl2O4 host can provide good environment to tune the emission color for the SrAl2O4:Eu3+Dy3+.
Abstract: The thermal stability of polypropylene (PP) based cellular electromechanical films was improved by compounding PP with thermally more durable cyclo olefin copolymer (COC) and polyhedral oligomeric silsesquioxane (POSS) nanochemical. The cast films were biaxially oriented in laboratory scale and then expanded by a gas diffusion expansion method, which increased the pore size inside the cellular film structure and the thickness of the film. The cellular films were then electrostatically charged by a contact charging method and metallized by gold sputtering. The samples were aged at 85°C showing that the d33 signal decreased from the original value, but remained at high level; more than 120 pC/N even after two weeks of ageing.
Abstract: ZrO2 sols were prepared with hydrothermal synthesis method. The ZrO2 films were characterized or examined by many kinds of instruments. With different content of zirconium oxychloride octahydrate, the particle sizes of ZrO2 sols are different from 3nm to 25nm. And 1-on-1 laser-induced damage threshold tests on ZrO2 films were carried out with a Q–switched Nd-YAG high power laser at 1064 nm. The experimental results showed that the ZrO2 sols is suitable for preparing ZrO2 thin film and the refractive index and thickness of this thin films achieve our requirement.
Abstract: A new chromophore containing azo group, 3,3'-dichloro-4,4'–di-(4-amino-azo-phenyl) -diphenylmethane (CAAPM), was synthesized based on 3,3'-dichloro-4,4'-diamino– diphenylmethane, sodium nitrite and benzenamine via diazo-coupling reaction. Azobenzene polyurethane (PU) containing chiral unit was obtained from CAAPM, chiral reagent L(-)-tartaric acid and isophorone diisocyanate (IPDI). The chemical structures of CAAPM and PU were characterized by FT-IR and UV-Vis spectroscopy. The measurements of refractive index (n) and thermo-optic coefficient (dn/dT) of polyurethane were demonstrated at complex light. The values of n and dn/dT were used to calculate the dielectric constant (ε) and its variation with temperature (dε/dT). The dn/dT is 4.2000～-3.7000×10-4°C-1. The conclusion has a little significance to develop new the digital optical switch (DOS).
Abstract: Some deviant breakdown-quenching characteristics of silicon photomultipliers are demonstrated and their physical mechanisms are explored. “Twice breakdown” phenomenon, “flat-topped” avalanche pulses are analyzed. These characteristics are explained in terms of avalanche threshold current based on the Haitz’s equivalent circuit model. The results show that the maximum over-voltage for a normal operating silicon photomultiplier equals the product of the avalanche threshold current and the quenching resistor of the avalanche photo-diode (APD) pixel, approximately.
Abstract: In this research, p-type porous silicon was successfully fabricated with a typical electrochemical etching method. The mixed solution of HF and absolute ethyl alcohol with different volume ratio was used as the electrolyte in this experiment. The anodic current density was 20 mA/cm2～60 mA/cm2. The luminous intensity of the PS samples increased with the increasing of the current density, the peaks of PL first red shift (from 692.1nm to 727.9nm) then blue shift (from 727.9nm to719.6nm). With the increasing of the concentration of HF, PS luminous intensity gradually decreases, and the peaks of PL gradually occurs red shift. And possible mechanisms of the growth and the photoluminescence of porous silicon were proposed to explain the experimental result．