All-optical diode effect of a nonlinear photonic crystal with a defect

An all-optical diode behavior that uses a nonlinear one-dimensional photonic crystal (NPC) with a defect Kerr medium is numerically simulated by the use of a nonlinear finite-difference time-domain (NFDTD) method.The numerical results show that for an incident pulse with appropriate intensity and temporal width,the transmittance can be several times greater in one direction of NPC than in the opposite direction at the pulse carrier frequency. This behaves like an all-optical diode and has promising applications in some areas such as optical isolation and all-optical processing.The ways to obtain low threshold of pulse field strength to realize an all-optical diode are also analyzed in detail.

Differentiation of storage time of wheat seed based on near infrared hyperspectral imaging

Seed aging during storage is one of the main factors that influence the quality of wheat seed.Current detection methods based on NIR spectra were mostly for group seeds,they had poor stability for single seed detection because of sample uniformity.In this study,the characteristic changes of single wheat seed during storage procedure were measured through hyperspectral imaging technology.Firstly,hyperspectral imaging data of wheat grain including six years from 2007 to 2012 had been collected.The original spectra showed clear difference in the band of 1400-1600 nm,which may be caused by the decreasing of moisture and protein content during storage;principal component analysis(PCA)was applied to analyze the spectral data of wheat grain including six years,the clustering chart of the principal components indicated that the grain between same or similar year have an clustering characteristic,and the characteristic difference would become obviously with the increasing of storage time;soft independent modeling of class analogy(SIMCA)was applied to classify the grain of different years,results showed that the classification accuracy of the dichotomy between adjacent years could reach 97.05%,and the accuracy of the mixed classification of six years could also reach 82.5%.These results indicated that hyperspectral imaging technology could be used to differentiate the quality change of wheat seed during different storage time,which could provide support for the intelligent monitoring of stored wheat seeds.

Photochromic effect of HoPO_4:Li^+ powder

Li^＋-doped HoPO4 powders with a pure tetragonal phase are successfully synthesized by the co-precipitation method. It exhibits an obvious color change under sunlight and tri-phosphor fluorescent light illumination. The introduction of Li^＋ ions into HoPO4 can further enhance its photochromic property effectively. The doped Li^＋ ions induce changes in the crystal structure. The spectral characteristics and thus photochromic properties of HoPO4 are explored. The improved HoPO4 powder, when used as a photochromic material, has wide-ranging prospects in security, decoration, and other applications.

Analytical drain current model for amorphous IGZO thin-film transistors in above-threshold regime

An analytical drain current model is presented for amorphous In-Ga-Zn-oxide thin-film transistors in the above-threshold regime,assuming an exponential trap states density within the bandgap.Using a charge sheet approximation,the trapped and free charge expressions are calculated,then the surface potential based drain current expression is developed.Moreover,threshold voltage based drain current expressions are presented using the Taylor expansion to the surface potential based drain current expression.The calculated results of the surface potential based and threshold voltage based drain current expressions are compared with experimental data and good agreements are achieved.