Abstract: We investigate the angular distribution of high harmonic generation (HHG) from impulsively aligned CO2 molecules driving by the femtosecond laser. We first observe the HHG spectra under the different aligning angles and the different laser intensities. The angular distribution is found to be sensitive to both the harmonic order and the intensity of the driving laser pulse. At last, we theoretically and experimentally demonstrate the angular distribution with the different harmonic orders and the different laser intensities.
Abstract: The random lasing emission from granular-surface PS:PMMA:Alq3:DCJTB blend films was investigated. By micro-phase separation of PS:PMMA:Alq3:DCJTB blend in spin-coating and solvent evaporation process, we obtained a granular-surface waveguide film with gain on glass substrates, whose period is about 200~500nm, and fluctuation is about 20nm. Pumped by THG YAG laser, a significant random laser emission was observed. Compared with the samples of glass/PMMA:Alq3:DCJTB and glass/ PS:Alq3:DCJTB prepared under the same conditions, the laser threshold decreased about 5 times, the line width at half (FWHM) reduced to 1.7nm from more than ten nm, and the quality factor of laser peak increased 7-9 times.
Abstract: For the purpose of stray light suppression, black anodized and sandblasted aluminum alloy is widespread used in spaceborne cameras. Base on the relative measuring method, in the white light irradiation, measure relative backscatter intensity and BRDF of two black anodized and sandblasted sample surfaces. Contrast these surfaces scattering characteristics. Finally BRDF curves have been drawn with measurement data. In the curves, the BRDF of sandblasted aluminum surface is nearly linear relation. Anodized surface curve, it’s pulse pattern that BRDF sharply increases among the region of critical angles. It is indicate that in critical angle range, anodized aluminum surface specularity is visible and can be treated as specular reflection which harm for stray light suppression. This experiment research can provide objective reference of these two material’s scattering characteristics in specific optical system design.
Abstract: Hybrid photovoltaic concepts based on a nanoscale combination of organic and inorganic semiconductors are promising way to enhance the cost efficiency of solar cells through a better use of the solar spectrum, a higher ratio of interface-to-volume, and the flexible processability of polymers. In this work, two types of thin film solar cells have been developed. In both types of solar cells, poly-N-vinylcarbazole (PVK) is used as electron donor, cadmium sulfide (CdS) and titanium dioxide (TiO2) nanocrystals are used as electron acceptors, respectively. Since TiO2 has a wide band gap and can only absorb UV light, in the second type of solar cell, ruthenium dye is used as photo-sensitizer. The preliminary results of photoconductive and photovoltaic characteristics of these two inorganic-organic composites are presented.
Abstract: The yellow luminescence (YL) band in unintentional doped n-GaN irradiated by 10 MeV electrons has been investigated by means of photoluminescence (PL) spectroscopy. The YL intensity increased after electron irradiation and thermal annealing, indicating that the deep level defects are created by electron irradiation and thermal annealing. These deep level point defect complexes arising from the irradiation introduced Ga vacancies and oxygen donor impurities are responsible for the YL.
Abstract: The nano Y2O2S:Eu 3+0.01 were prepared with solvohtermal method. Using ethylenediamine as solvent, at 220°C for 12h , we get the best sample. The effect of various reaction times, surfactant in reaction on nano-particle size of the products were investigated in detail. Using the Laser granularity cryoscopy（rise 2008）to display the products size, the result shows that the sample size about 45nm, and the SEM shows that the morphology are nano wires. The emission spectrum shows that the strongest peak is located at 625nm, which attributed toEu 3+ ions’5D0-7 F2 transition.
Abstract: We present the design and fabrication of metamaterials, and investigated the power transmission properties of the metamaterials in the frequency ranging from 1.04THz to 4.25THz. The measured results reveal a global maximum transmission peak at 2.52THz. We compared measured power transmission performances of four types of metamaterials microstructures, and analyzed their transmission differences.
Abstract: Complicated microwave cavity loaded with ceramics is first investigated by mode matching method in rubidium frequency standard. In order to study main factors influencing resonant characteristics, resonant frequencies of TE011 mode are calculated and compared with commercial software (CST) results. The results show good agreement between theoretical computations and CST simulations. This work is of great significance for cavity design and theory perfection in atomic frequency standard.
Abstract: In this work, the preferential chemical etching of dislocations on (0001) sapphire surface was investigated. The sapphire was etched by fused KOH etchant at fixed temperature for different time. The differences in the morphology of the etch pits on c-plane sapphire were observed by the optical microscope and atomic force microscopy. The results show that the optimal condition for dislocation displaying was etching 15 min or 25 min with fused KOH at 290 °C.The morphologies of the etch pits were changed from the triangle to the polygon and three kinds of increscent mechanisms about the etch pits are put forward and discussed in the paper.
Abstract: In this paper, the influence of reactor pressure on the quality of GaN epilayer grown by Hydride vapor phase epitaxy (HVPE) is reported. A series of sample was fabricated at 0.2, 0.5, 0.7 and 1 atm. There were several samples at certain pressure in order to avoid the random affection. And the root mean square (RMS) is introduced to determine the repeatability. The rocking curve and photoluminescence spectrum are used to evaluate the quality of the grown epilayer. The reactor pressure has affection on the quality of GaN epilayer. Low reactor pressure is helpful to improving the quality of crystal structure.