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Three-inch InGaAs epilayers are grown by solid source molecular beam epitaxy using the manipulator equipped with dual-zone heaters. The effects of the substrate temperature on the uniformity of material surface morphology, indium composition, photoluminescence, electronic mobility, and background doping are investigated. As the temperature of the outer heater in the range of 625 °C to 655 °C, no dim area is observed on the edge of the material surface. At the same time, the indium composition fluctuation of the high-resolution X-ray diffraction and the photoluminescence wavelength fluctuation are less than ±0.1% for the epilayers grown at the optimum substrate temperatures.

Offshore wind power is a rapidly growing area of electricity in China. In the present paper, interaction mechanisms between the caisson for wind turbines and saturated silt sand are investigated with laboratory tests based on two different installation methods, jacking installation and suction installation. For the jacking installation process, the results indicate that the soil pressures inner and outer the skirt of the caisson vary with a similar feature and the magnitudes of the two are nearly balanced. The tip resistance plays a key role in the total jacking installation resistance. This paper examines the predictive performance of qc method and API approach for jacking installation resistance. It is demonstrated that the qc method provides better predictions. The resistance coefficients are recommended. For the case of suction installation, however, the changes of soil pressures inner and outer the skirt are contrasting. Specifically, the inner pressure and tip resistance fall dramatically, but the outer pressure increases when suction is applied. Seepage effect is found to be an important mechanism for the installation of suction caisson. The reduction ratios of the inner friction and tip resistance follow a power-function with the normalized suction. Based on the test results, a prediction method for the required suction has been developed and evaluated.

Research on the safety of powerhouse in a hydropower station is mostly concentrated on the vibration of machinery structure and concrete structure within a single unit. However, few studies have been focused on the vibration transmission among units. Due to the integrity of the powerhouse and the interaction, it is necessary to study the vibration transmission mechanism of powerhouse structure among units. In this paper, field structural vibration tests are conducted in an underground powerhouse of a hydropower station on Yalong River. Additionally, the simplified mechanical models are established to explain the transmission mechanism theoretically. Moreover, a complementary finite element (FE) model is built to replicate the testing conditions for comprehensive analysis. The field tests results show that: (1) the transmission of lateral-river vibration is greater than those of longitude-river vibration and vertical vibration, (2) the vibration transmission of the vibrations that is caused by the low frequency tail fluctuation is basically equal to that of the vibrations caused by rotation of hydraulic generator. The transmission mechanism is demonstrated by the simplified mechanical models and is verified by the FE results. This study can provide guidance for further research on the vibration of underground powerhouse structure.

A direct correlation pathway has been established between the material defects and dark currents of InGaAs photodetectors, which is significant for demonstrating the focal plane array with large scale and small pixels. The same photodetector chip was characterized by using emission microscopy and dark current-voltage measurements. The chips with defect emissions perfectly match with those chips showing large dark currents. The defect emissions were observed for the chips with large dark currents, while did not for the chips with low dark currents. The measurement result of the transmission electron microscope reveals that those material defects correlated with the device dark currents were mainly originated from the interface of the substrate and InP buffer layer. This work clarifies the direct correlation of defect types and device performances, which indicates the direction of improving the photodetector materials.

High-quality InP is grown by solid source molecular beam epitaxy using white phosphorus source in a three-zone valved cracker cell. The growth temperature, growth rate and substrate desorption process have been adjusted to optimize the structural, electrical and optical properties. The photon and carrier scattering dynamics are investigated by temperature-dependent photoluminescence and electron Hall mobility. The 5-μm-thick sample presents stronger photoluminescence, solo carrier recombination scheme and inferior impurity scattering comparing to the 1-μm-thick sample. The high electron mobility of 137000 cm2/V·s at 77 K has been achieved for the 5-μm-thick InP layer.

Three Schiff bases dissolved in chloroform were investigated to determine their nonlinear optical properties using D4σ Z-scan technique employing 10 ps pulses of Nd:YAG laser at 355 nm. It was found that the highest value of the nonlinear refractive index was obtained for Schiff base with 2-(2-pyridyl)ethylamine. Whereas, a negative nonlinear refractive index was extracted for symmetrical Schiff base with cyclohexanediamine with NO2 group. In addition, the Schiff base thin films were investigated using AFM and SEM/EDX measurements to check their quality and homogeneity, which is necessary in the production of photonic devices.

In this work, we report preliminary results obtained for methacrylic polymers incorporating azobenzene side-group as nonlinear optical (NLO) active molecule. The trans-cis isomerization properties are discussed. The third-order non-resonant nonlinear refractive index (n2) and nonlinear absorption coefficient (β) are measured using the Z-scan technique at 1064 nm in the picosecond regime. The influence of different electron-acceptor groups in azobenzene moieties on the nonlinear properties is investigated.

The newly introduced imaging Dark-field Z-scan (DFZ-scan) technique is applied here to demonstrate its ability to measure the optical third-order nonlinear (NL) index coefficient in the presence of nonlinear absorption (NLA). We present our experimental results for two compounds of Porphyrin molecules, known to have relatively high NLA in the picosecond regime, at 532[Formula: see text]nm, allowing to test both cases of positive and negative nonlinear refraction (NLR). Moreover, we show that, it is possible to increase the sensitivity of the method by introducing a circular aperture in the image plane. Also, limitations are discussed to process optically a pure NL refractive signal, not subject to the influence of the NLA one, at the output of the imaging setup.