Search

Terahertz region is the electromagnetic gap between the infrared optoelectronics and the high frequency electronics, which is of broad prospects in applications. The application requirements drive the rapid development in Terahertz technologies including sources, detectors and systems. In the last two decades, quantum cascade laser has made great progress as one of the most promising terahertz sources. In this paper, we present the development of terahertz quantum cascade lasers in our group.

As a system with both profound physics and promising application potentials, the strain-induced self-assembled semiconductor nanostructures have been investigated for decades of years. The optical and electrical properties of this system are mainly determined by the nanostructures, but can be greatly affected by the generally existent two dimensional structures from which the nanostructures evolve, the so called wetting layer (WL). The WL configurations can be varied with different growth conditions, and further influence the nanostructure morphology and properties. This is a reviewing article introducing some recent progresses in investigating the evolution of WLs in InAs/GaAs system with reflectance difference spectroscopy. Different kinds of WL evolution processes in Stranski-Krastanov growth mode are introduced. The segregation and desorption of indium atoms and the effect of growth interruption are mentioned. The existence and the evolution process of wetting layers in droplet epitaxy method are also discussed.

In this paper, thick 4H-SiC epilayers of 147 μm demanded for ultra-high-voltage power devices has been obtained at a high growth rate of 85 µm/h under optimized growth conditions. We have attempted to improve the quality and reduce the surface defect density of thick epilayers. The surface defect density is obviously reduced from 3.46 cm−2 to 0.85 cm−2, owing to the addition of the etching process. The effect of the etching process on the surface defect is discussed based on the measured results. The results demonstrate that the fast epitaxial growth system can grow ultra thick 4H-SiC epilayers with high quality that satisfies the requirement of ultra-high-voltage devices.

HEPS-BPIX3 is a hybrid pixel detector readout chip for X-ray applications for the High Energy Photon Source (HEPS) in China. The readout chip contains an array of 88 × 88 pixels with a pixel size of 55 μm × 55 μm, working in single photon counting mode. Each pixel handles both polarities of positive and negative input charge signals and has a counting depth of 11 bits. Using a clock with a frequency up to 160 MHz, the chip can read out serially with zero dead time. Designed in a 130 nm CMOS technology, the chip has been measured and given the CSA charge gain of 17.6 mV/ke- for electron collection and 13 mV/ke- for hole collection, respectively. Bump-bonded detector modules with a 320-μm-thick silicon sensor were also tested. The test results showed an equivalent input noise of 156 e- and a counting rate up to 2.2 Mcps. Besides, an image using an X-ray tube was demonstrated and a frame rate of 1.8 kHz could be guaranteed. Measured characteristics present the normal functionality of the HEPS-BPIX3 chip and prove that the chip satisfies the HEPS requirements.

The flexible phosphor film consists of green Y3Al5O12: Ce3+ phosphors, red CaAlSiN3: Eu2+ phosphor and common silicone by spin coating method. The phosphor film was aged by xenon lamp ageing, high ...

We developed a novel compact structure, called a Coupled RFQ-SFRFQ (CRS), to accelerate a 0.8 MeV helium beam for a materials irradiation project. A high accelerating efficiency was achieved by replacing the accelerating section of the radio frequency quadrupole (RFQ) with a separated-function radio frequency quadrupole (SFRFQ) structure, in a single cavity. Following the electromagnetic simulations, RF measurement of the CRS cavity was performed, including low RF power and high RF power measurement. Recently, beam experiments on the CRS linac indicated that the maximum accelerated beam current could reach 2 mA with an energy of 0.8 MeV and energy spread (FWHM) of 3.1%. The experimental measurement results showed good consistency with the beam dynamics simulations.

The relative collection efficiency (CE) of 20-inch Photomultiplier Tubes (PMTs) cannot be measured directly, but it can be obtained by the quantum efficiency (QE) of the photocathode and the relative detection efficiency (DE) of the PMTs. The measurements of relative CE and its spherical uniformity of the 20-inch PMTs have been introduced in this manuscript, and the difference in performance between Microchannel-Plate PMT (MCP-PMT) and Dynode-PMT were shown. The CE performance for 20-inch PMTs are given and the batch test results of CE for MCP-PMTs and Dynode-PMTs are compared at the end of this manuscript.

Orthotropic steel decks are vulnerable to fatigue cracking in welded connections and complex geometrical details. A total of three fatigue tests were conducted on segments of orthotropic steel deck to evaluate the fatigue performance of trough-to-crossbeam connections with various cut-out configurations. In the tests, the specimens were subjected to cyclic three-point bending load and the fatigue cracks were more likely to initiate from the cope holes in the crossbeam web rather than the trough-to-crossbeam fillet welds. Three-dimensional finite element models (FEM) of the specimens were built and validated by the measured deflections and stresses. Using the validated FEM, the characteristic stresses based on the theory of critical distances (TCD) were calculated for the stress concentrations along the cope holes. The fatigue crack initiation life, predicted by the TCD-based stress combined with the plain material S–N curve, agreed reasonably with the fatigue test results. The TCD method could further form a basis of fatigue crack propagation analysis using the fracture mechanics approaches.

An experimental set-up has been developed to study the influence of ambient temperature on the performance of 20-inch PMTs. The temperature was adjusted and controlled by a thermostat within a large range of -40 to +40oC. The temperature dependences of typical PMT parameters were measured by registering and analyzing signal waveforms of the PMTs. Two types of 20-inch PMTs with Dynode and MCP multiplier were tested, and their performance was compared at different ambient temperature. It is shown that the signal waveforms of the MCP-PMT prototype are more sensitive to ambient temperature than that of the Dynode-PMT prototype. Ambient temperature has little effect on the time performance of both types of large area PMTs. The dark counting rate of different types of PMTs has a similar trend with the change of temperature, and approximately conforms to the exponential rising law within the examined temperature range. The experimental results show that DCR (dark counting rate) increases by about 15% with 1oC temperature increase in the range of 15 to 30oC.

A high intensity four-vane continue wave (cw) RFQ for the Beijing Isotope Separation On-Line (BISOL) high intensity deuteron driver linac has been designed. This RFQ will accelerate the 25 mA cw deuteron beam the 3.0 MeV with an operating frequency of 162.5 MHz. Three beam dynamics design schemes based on different strategies have been proposed and detailed comparisons, including tolerance study and error analysis, are performed to evaluate them. The final design of RFQ can achieve the requirements with a length of 5.29 m and the transmission of 99.1%. The inter-vane voltage is ramped from 60 kV to 75 kV and the maximum Kilpatrick factor is 1.42, which is very modest and beneficial to cw operation mode. The RFQ electromagnetic design is carried out based on the full-length 3D model, including vane modulation, undercuts, π-mode stabilization rods (PSLs) and tuners. The requirements of correct work frequency and voltage ramp are fulfilled by varying vane width and adjusting undercuts. In addition, the π-mode stabilization rods (PSLs) are inserted and optimized to increase mode separation and enhance voltage stabilization. The rf power loss and effective shunt impendence are 118 kW and 210 kΩ⋅m, respectively. In addition, multi-physics analysis of the cavity, based on the electromagnetic codes CST MWS, HFSS and ANSYS, has been carried out to check the cooling system, the temperature rise and deformation of the cavity, as well as the frequency shift in the cw operation. Finally, the frequency sensitivities to cooling water temperature are studied to obtain water temperature tuning coefficients, which will be used for fine tuning of the RFQ cavity during operation.

The characterization and classification of white blood cells (WBC) is critical for the diagnosis of anemia, leukemia and many other hematologic diseases. We developed WBC-Profiler, an unsupervised feature learning system for quantitative analysis of leukocytes. We demonstrate that WBC-Profiler enables automatic extraction of complex signatures from microscopic images without human-intervention and thereafter effective construction of leukocytes profiles, which decouples large scale complex leukocytes characterization from limitations in both human-based feature engineering/optimization and the end-to-end solutions provided by modern deep neural networks, and therefore has the potential to provide new opportunities towards meaningful studies/applications with scientific and/or clinical impact

From a new viewpoint to improve plate plan view pattern during hot rolling, a plate edging process was proposed to roll back only the plate width spread of conventional rolling in this paper. Using commercial finite element (FE) analysis software DEFORM-3D, a three-dimensional rigid plastic FE model for vertical–horizontal (V–H) hot rolling was developed on the basis of a 5 m wide and heavy plate mill. Three hundred and twenty kinds of different V–H rolling processes were simulated by the FE model. Basing on the simulation results, the formation laws of dog bone shape during the vertical rolling and the width spread behaviours during the horizontal rolling were clarified. A plate edging model predicting the plate edging efficiency was established with the aid of an artificial neural network. The plate edging efficiency predicted by this plate edging model agreed well with those predicted by the existing strip edging models when the slab width/thickness ratio was small, which confirmed the validity...

The cement clinker manufacturing process is a complex process which involves energy conversion and consumption. The objective of this study is to establish the thermal efficiency analytic model of this process. Energy flow models of the whole process and its three process units of raw material preheating & decomposition, clinker calcination, clinker cooling are established in this paper. The thermal efficiency of the whole process is quantitatively described based on the energy consumption fraction of each process unit. Energy consumption fractions of the three process units in a cement plant are 1.15, 0.43 and 0.47 respectively. It shows that the thermal efficiency of the raw material preheating & decomposition process unit has the greatest impact on the thermal efficiency of the whole process, successively followed by the clinker cooling and clinker calcination process units. Methods to improve the thermal efficiency of the whole process are discussed.

// Ye Wang 1, 2, 3 , Jufeng Xia 1, 2, 3 , Zhaoyuan Fang 1, 2, 3 , Fei Li 1, 2, 3 , Duo Li 1, 2, 3 , Zuoyun Wang 1, 2, 3 , Yan Feng 1, 2, 3 , Jian Zhang 1, 2, 3 , Haiquan Chen 6, 7 , Hongbin Ji 1, 2, 3, 5 , Hongyan Liu 1, 2, 3, 4 1 CAS Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, Shanghai, 200031, China 2 CAS Center for Excellence in Molecular Cell Science, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, Shanghai, 200031, China 3 Innovation Center for Cell Signaling Network, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, Shanghai, 200031, China 4 Institute of Basic Medicine, Shandong Academy of Medical Sciences, Jinan, 250062, Shandong, China 5 School of Life Science and Technology, Shanghai Tech University, Shanghai, 200120, China 6 Department of Thoracic Surgery, Fudan University Shanghai Cancer Center, Shanghai, 200032, China 7 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, 200032, China Correspondence to: Hongyan Liu, email: hyliudycui@aliyun.com Hongbin Ji, email: hbji@sibcb.ac.cn Keywords: lung adenocarcinomas, BMXΔN, cell proliferation, migration, skipping variant Received: January 12, 2017 Accepted: March 22, 2017 Published: April 03, 2017 ABSTRACT The non-receptor tyrosine kinase BMX has been reported in several solid tumors. However, the alternative splicing of BMX and its clinical relevance in lung cancer remain to be elucidated. Exon1.0 array was used to identify a novel alternative splicing of BMX, BMXΔN , which was confirmed by rapid amplification of cDNA ends and reverse transcription-polymerase chain reaction. BMXΔN , resulting from exon skipping with excluding exon 1 to exon 8 of BMX gene, was found in 12% human lung adenocarcinoma specimens. BMXΔN is not found in paired pathologically normal lungs and positively correlated with EGFR mutation in lung adenocarcinomas. Moreover, BMXΔN increases cell proliferation, neoplastic transformation, and migratory property of human non-small cell lung cancer cells. The function of BMXΔN in lung cancer might be presumably due to enhanced ERK signaling.

A sticker breakout is a significant occurrence which not only disturbs steady state casting but also reduces plant productivity and efficiency. Optimising the casting parameters and increasing the accuracy rate of breakout prediction systems are two effective measures for reducing breakouts. In the present paper, plant data were collected and the influence of casting parameters such as slab dimension, casting speed and mould level on sticker breakouts were analysed, especially the effect of heat flux. In addition, sticker propagation behaviour characteristics, including vertical velocity, horizontal velocity and propagation angle, were investigated by measuring the temperature of the mould copper plates. These results provide a reference for optimising the casting parameters and enhancing the accuracy of breakout prevention systems.

The sources of elemental (EC) and organic carbon (OC) aerosols in Asian outflow were investigated in the spring of 2015 in terms of radiocarbon (14C) and molecular marker analyses. The contribution of fossil fuel (FF) sources to carbonaceous aerosols (TC) significantly increased in polluted air masses with enhancements in the concentrations of carbon monoxide. For EC, FF sources dominated in the polluted air masses. For OC, the contributions of non-FF sources other than biomass burning (BB) were found to be significant (comparable to or higher than those of FF sources), especially in air masses with higher values of the water-soluble fraction of OC (fWSOC) and 14C concentrations (F14C). Positive correlations between fWSOC and F14C indicate that the origins of TC (mainly OC) have great impacts on the water solubility variability and the subsequent cloud formation processes of OC during transport. We found the importance of natural sources as possible origins of OC in non-polluted (i.e., background) air. This study raises the need to further investigate the source apportionment of OC, especially its natural origins, for more accurately assessing the climatic impacts of EC and OC in East Asia.

Room-temperature pulsed and continuous-wave (cw) operation of a tunable external cavity (EC) quantum cascade laser (QCL) at an emitting wavelength of $$4.7\,\upmu \hbox {m}$$ was presented. The effect of different external cavity lengths and grating angles of the EC–QCL system were analyzed numerically. A wide tuning range greater than $$131\,\hbox {cm}^{-1}$$ was obtained in pulsed mode at room temperature. Without the anti-reflection coating procedure, single-mode cw operation with a side-mode suppression ratio (SMSR) above 20 dB and a wide tuning range greater than $$116\, \hbox {cm}^{-1}$$ were achieved. Near the center region, SMSR about 30 dB was also realized through designing the external cavity length. Strain-compensation combined with two-phonon resonance in an active region design and the high-reflection coating promised low threshold current density. A record low threshold current density of $$0.901\,\hbox {kA/cm}^{2}$$ for an EC–QCL operated in cw mode was realized.

Photoluminescence properties of porous InP are found to be strongly affected by infilling ferroelectric polymers. Based on the temperature- and excitation-power-dependent photoluminescence, the intensity suppression and blue shift of the near-band-edge emission are supposed to result from the passivation of surface states by introducing ferroelectric polymers. On the other hand, the significant enhancement of deep-level emission is caused by the increased concentration of phosphorus vacancies due to ion exchange when infilling the ferroelectric polymers into porous InP. The surface passivation of porous InP by ferroelectric polymers is useful for improving the performances of InP-based electronic and optoelectronic devices.

In this study, hydrogenated amorphous silicon (a-Si:H) single junction and amorphous/microcrystalline silicon tandem (a-Si:H/µc-Si:H) solar cells with different back-reflectors (BRs) are systematically investigated. A novel white polyvinyl butyral (PVB) foil was used as BR. In addition, the specular aluminum (Al) films and rough Al films were deposited on back float glasses as BRs as well, which were integrated onto the front glass covered with solar cells by laminating with a transparent PVB encapsulation foil. It is found that both types of solar cells (a-Si:H and a-Si:H/µc-Si:H) with white PVB foil BRs show a higher short circuit current density (Jsc) compared to the cells with a specular Al BR. It is mainly due to a high light scattering of white PVB foils. Moreover, the cell with a rough Al film BR shows a low Jsc close to that of cell without any BRs. The great light losses inside the solar cell may be mainly caused by the plasmonic absorption on the rough Al film surface. An a-Si:H solar cell of 8.3% and an a-Si:H/µc-Si:H tandem solar cell of 10.1% were obtained, in which the white PVB foils were used as BRs.

The degradation behaviors of hydrogenated amorphous/microcrystalline silicon (a-Si:H/µc-Si:H) tandem solar cells are systematically investigated. It is found that the degradation of the tandem solar cells takes place not only under the light soaking but also after dark storage. The degradation in the efficiency of tandem solar cells is mainly due to a reduction of fill factor (FF) in our study. Different from light-induced degradation (LID) behaviors for the tandem solar cells, the degradation behaviors under dark storage, i.e., the dark degradation could be mainly caused by the cracks or voids formed in the bottom µc-Si:H cell. These defects could lead to an oxidization of internal silicon surfaces by the oxygen atoms. The stabilities of the top a-Si:H cells and the ZnO:B electrodes are also investigated. Furthermore, adjusting the crystallinity of intrinsic µc-Si:H material and inserting an intermediate light reflective (ILR) layer between the top cell and bottom cell can improve the performances of the novel structure tandem solar cells. A gain of 0.7% in efficiency is achieved, and meanwhile no dark degradation is observed for the novel tandem solar cells.

Introduction A national survey on critical values in hematology of China laboratories was conducted to determine the current practice and assess the quality indicators so as to obtain a quality improvement. Methods Laboratories participating were asked to submit the general information, the practice of critical value reporting, and the status of timeliness of critical value reporting. Results A total of 862 laboratories submitted the results. The majority of participants have included white blood cell count, blood platelet count, hemoglobin, prothrombin time, and activated partial thromboplastin time in their critical value lists. Many sources are used for establishing a critical value policy, and some of the laboratories consult with clinicians. The unreported critical value rate, late critical value reporting rate, and clinically unacknowledged rate in China are relatively low, and the median of critical value reporting time is 8-9 minutes. Conclusion There exists a wide variety for critical value reporting in hematology in China. Laboratories should establish a policy of critical value reporting suited for their own situations and consult with clinicians to set critical value lists. Critical values are generally reported in a timely manner in China, but some measures should be taken to further improve the timeliness of critical value reporting.

We demonstrate room-temperature operation of broad-area edge-emitting photonic-crystal distributed-feedback quantum cascade lasers at λ ∼ 4.6 μm. The lasers use a weak-index perturbed third-order photonic-crystal lattice to control the optical mode in the wafer plane. Utilizing this coupling mechanism, the near-diffraction-limited beam quality with a far-field profile normal to the facet can be obtained. Single-mode operation with a signal-to-noise ratio of about 20 dB is achieved in the temperature range of 85–290 K. The single-facet output power is above 1 W for a 55 μm × 2.5 mm laser bar at 85 K in pulsed mode.

Boron doped zinc oxide (ZnO:B) films with different thicknesses were prepared with low pressure chemical vapor deposition (LPCVD) technique and implemented in thin film silicon solar cells as front and back electrodes. It is found that thick back ZnO:B film electrode in thin film silicon solar cells leads to a high fill factors (FF), which is attributed to an improvement of the electrical properties of the thick ZnO:B films, and in the meanwhile a slightly low short circuit currents ( J sc ) due to a high light absorption in the thick back ZnO:B films. Differently, the thicker front ZnO:B film electrodes result in a high J sc but a low FF of solar cells compared to the thinner ones. The low FF of the solar cells may be caused by the local shunt originated from the pinholes or by the cracks (zones of non-dense material) formed in particular in microcrystalline silicon materials deposited on rough front ZnO:B films. As to the high J sc , it is expected to be due to a good light trapping effect inside solar cells grown on rough front ZnO:B films. Moreover, the application of high reflective polyvinyl butyral (PVB) foils effectively enhances the utilization of incident light in solar cells. By optimizing deposition process of the ZnO:B films, high efficiencies of 8.8% and 10% for single junction thin film amorphous silicon solar cells (a-Si:H, intrinsic layer thickness

We report the difference-frequency generation (DFG) of ultrafast mid-infrared laser radiation around 3 μm between two picosecond laser pulses with the center wavelengths of 800 nm and 1064 nm in a MgO:PPLN crystal at room temperature. The two laser pulses were generated from the actively synchronized picoseconds Ti:sapphire and Nd:YVO4 oscillators. We measured the DFG wavelengths tunable from 3.19–3.29 μm and the output power is potential to be several mW. This experiment proves a possible roadmap for ultrafast mid- and far-infrared laser radiation generation and even for the THz radiation.

Postgrowth rapid thermal annealing (RTA) was used to modify the optical properties of self-assembled InAs quantum dots (QDs) embedded in a photonic crystal nanocavity. Compared with the reference QDs in the unpatterned regions, it was found that the effect of RTA on the luminescence blueshift of QDs embedded in the nanocavities is similar to that from the unpatterned regions. However, InAs QDs in nanocavities exhibit an anomalous variation of luminescent linewidth during the course of RTA. This could be attributed to the deterioration of InAs QDs at the edge of photonic crystal air holes at high annealing temperatures. The stable position of cavity modes during the RTA temperatures shows the RTA technique could be applied to tune the spectral coupling of QDs/cavities when the QD spectra are on the red side of a cavity mode.

This paper mainly investigates the multiple confined modes of GaAs L 3 photonic crystal two-dimensional (2-D) structure using single layers of InAs quantum dots as active internal light sources. Theoretical calculations for the wavelength, quality ( Q ) factors and polarization of modes are compared to experimental data for L 3 photonic crystal nanocavities with end-hole displacements for s = 0 a and s = 0.15 a . It is found that a L 3 photonic crystal nanocavity includes five resonant modes and an end-hole displacement not only improves the Q factor of the fundamental mode but also strongly redshifts those modes which have large end-hole-field overlaps, thus reordering the modes. This understanding of the high-order modes should be particularly useful for the selective excitation of emitters that are strongly coupled to the cavity.

Random fatigue limits are experimentally studied on China grade B cast steel wheel. Test data were obtained by employing a so-called small sampling up-and-down test method. Results reveal that fatigue cracks of the present material were commonly initiated from the casting flaw of shrinkage cavities and grew with typical fatigue river-like flowers and striations. To address the scattered test data, randomness of fatigue limits are comparably measured by the existent four approaches, i.e. conventional, Dixon-Mood, Zhang-Kececioglu, and Zhao-Yang approaches. It is verified that Zhao-Yang approach is appropriately applied for the present assessment on random fatigue limits of China grade B cast steel wheel.

We demonstrate a high-power diode side-pumped Nd:YAG laser on the low gain three lines near 1.1 μm. By tuning the tilting angle of a solid etalon in the cavity, the laser can be selectively operated at 1112, 1116 and 1123 nm either in continuous-wave (CW) mode or in actively Q-switched (QS) mode, respectively. The highest average CW output powers were 75, 47 and 71 W at 1112, 1116 and 1123 nm, respectively. The transmittances of the etalon were calculated to analyze the performance of the laser at the three lines. Furthermore, a computational model of a three-wavelength laser based on rate equations was employed to examine the line selectivity of the three lines near 1.1 μm at different tilting angles of the etalon.

We report a high-power, narrow linewidth and tunable quasi-continuous-wave (QCW) yellow laser system at 589.159 nm. The system is of a design employing single-pass sum-frequency generation (SFG) in a LBO crystal by mixing the 1064 nm with 1319 nm lines from a two diode-side-pumped Nd:YAG master oscillator-power amplifier (MOPA) laser system. With the pump power of 35 W at 1064 nm and 25 W at 1319 nm, a 7.5 W QCW output of the SFG yellow laser at 589.159 nm, which is the vacuum wavelength of a general sodium D2 line, is obtained with a linewidth less than 0.7 GHz and a beam-quality factor M 2=1.2. The wavelength of the laser can be precisely step-tuned from 589.148 to 589.167 nm with an increment of 0.13 pm by means of a temperature-controlled etalon.

The authors developed a fast simultaneous method in detecting multi-gases using quantum cascade laser (QCL) based photoacoustic (PA) spectroscopy. We demonstrated the simultaneous measurement of CO and SO2 concentrations using two QCLs working at 4.56 and 7.38 μm, corresponding to the absorption bands of CO and SO2, respectively. The modulation frequencies of the two QCLs were 234 and 244 Hz. The response time was 0.6 seconds. A computer sound card was used to process the PA signals. Fast Fourier transform was an essential step to get the amplitudes of the PA signals at different frequencies. The concentration of each gas can be obtained from the PA signal amplitude at the corresponding modulation frequency.

In this work, we have adopted photoluminescence (PL) to study the evolution of self-assembled InAs/GaAs quantum dots (QDs) as a function of InAs deposition amount. With increasing InAs amount, the QDs transfer from unimodal to bimodal size distribution. Moreover, the PL peak of small-size QDs gradually deviates from the well-known anomalous temperature dependency of QDs, and follows the InAs intrinsic bandgap redshift at large deposition amount, whereas the PL peak of large-size QDs demonstrates the anomalous temperature dependency within the investigated deposition range. This indicates the small-size QDs are progressively detached from WL. The observations are interpreted with respect to different growth mechanisms of the two QDs families: the large-size QDs locate on the terraces and expand their sizes at the expense of the floating indium atoms, and the small-size QDs are at the step edges and grow by eroding WL.

Both In2O3 and ZnO are potential oxide semiconductor materials for optoelectronics devices. Semi-polar (101) plane wurtzite ( w -)ZnO films were grown on bcc-In2O3(111) by metal organic chemical vapor deposition and the epitaxial relation is w -ZnO(101) ∥ b c c - In 2 O 3 ( 111 ) . We have measured the valence band offset (VBO) of w -ZnO(101)/bcc-In2O3(111) heterojunction to settle the question of the band line-up of the ZnO/ In2O3 heterojunction. Our result shows that the valence band maximum (VBM) of ZnO (101) lies ∼ 0.49 eV below the VBM of bcc- In2O3(111), and the conduction band maximum (CBM) of w -ZnO(101) is about 0.05 eV lower than the CBM of bcc-In2O3(111), which shows that their CBMs are nearly at the same level.

This paper describes the design and fabrication process of a two-dimensional GaAs-based photonic crystal nanocavity and analyzes the optical characterization of cavity modes at room temperature. Single InAs/InGaAs quantum dots (QDs) layer was embedded in a GaAs waveguide layer grown on an Al"0"."7Ga"0"."3As layer and GaAs substrate. The patterning of the structure and the membrane release were achieved by using electron-beam lithography, reaction ion etching, inductively coupled plasma etching and selective wet etching. The micro-luminescence spectrum is recorded from the fabricated nanocavities, and it is found that some high-order cavity modes are clearly observed besides the lowest-order resonant mode is exhibited in spite of much high rate of nonradiative recombination. The variance of resonant modes is also discussed as a function of r/a ratio and will be used in techniques aimed to improve the probability of achieving spectral coupling of a single QD to a cavity mode.

Micro Pattern Gas Detector (MPGD) coupled to an optical imaging system is a good candidate for detecting polarization of X-ray, dark matter, neutron, etc. In this paper, a MicroMegas detector is designed for detecting the photoelectron track of X-ray, which working gas compose of an Ar+CF4 mixture and optical signal readout with an ICCD. The correlation of scintillation light intensity and electrical current is obtained in the varying strength of the electric field at avalanche region, and the position resolution is 385 mu m. The clear track images of the Am-241 alpha source and 5.9 KeV X-ray are obtained, and the X-ray imaging is achieved in the experiment.

In order to meet the increasing demand for high-quality miniature parts made of a wide variety of materials, the electronics, biomedical and optical industries are moving towards micro/nano-machining. Currently, mechanical micromachining can only be performed under very low feed rates and small depth of cut, which makes it very difficult to reach reasonable productivity. To cope with the low-productivity problem for micro/nano-machining of high-precision molds or miniature parts, a highly accurate and productive machining center has been designed and developed in this paper. The developed machine tool is equipped with counter balance axes, and each axis is driven at its center of gravity to achieve high acceleration/deceleration without causing any vibration. This paper describes the theoretical and practical background of the design of the machine tool and its control and measurement system. Then, experiments are carried out to evaluate the machining performance of this designed machine tool.

X-ray photoelectron spectroscopy has been used to measure the valence band offset of the ZnO/BaTiO3 heterojunction grown by metal-organic chemical vapor deposition. The valence band offset (VBO) is determined to be 0.48±0.09 eV, and the conduction band offset (CBO) is deduced to be about 0.75 eV using the band gap of 3.1 eV for bulk BaTiO3. It indicates that a type-II band alignment forms at the interface, in which the valence and conduction bands of ZnO are concomitantly higher than those of BaTiO3. The accurate determination of VBO and CBO is important for use of semiconductor/ferroelectric heterojunction multifunctional devices.

InN films with electron concentration ranging from n similar to 10(17) to 10(20) cm(-3) grown by metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were investigated by variable-temperature photoluminescence and absorption measurements. The energy positions of absorption edge as well as photoluminescence peak of these InN samples with electron concentration above 10(18) cm(-3) show a distinct S-shape temperature dependence. With a model of potential fluctuations caused by electron-impurity interactions, the behavior can be quantitatively explained in terms of exciton freeze-out in local potential minima at sufficiently low temperatures, followed by thermal redistribution of the localized excitons when the band gap shrinks with increasing temperature. The exciton localization energy sigma (loc) is found to follow the n (5/12) power relation, which testifies to the observed strong localization effects in InN with high electron concentrations.

In order to create a higher torque spindle system for productive milling operations, rotational speed stability against the torque disturbance has been studied with respect to the spindle mechanical design parameters, actuator types and spindle control algorithms. The study showed a remarkable difference in the spindle rotational speed stability against torque disturbance between a spindle system equipped with an induction servo motor and a permanent magnet synchronous servo motor. The results of this study have been obtained by theoretical analysis, numerical simulation and physical experiments, and the experimental study showed that the hybrid actuation spindle achieves longer tool life.

We have presented theoretical and experimental investigations of nanosecond (ns) deep-ultraviolet (DUV) 177.3 nm radiation by means of second harmonic generation (SHG) from a frequency-tripled Nd:YAG laser (355 nm, 49 ns and 10 kHz) in KBe2BO3F2 (KBBF) nonlinear crystal for the first time. A DUV KBBF-SHG numerical model, accounting for linear absorption, pump depletion, beam spatial birefringent walk-off and diffraction, is performed in the Gaussian approximation of spatial and temporal profiles. In the experiment, a maximum average output power of 14.1 mW at 177.3 nm was obtained. The dependence of 177.3 nm output power on the 355 nm pump power was simulated. The calculated results are in good agreement with the measured data. We used the model further to investigate the optical conversion efficiency, pulse width, beam spatial intensity profile and beam quality factor of the generated 177.3 nm light, in particular the effect of beam birefringent walk-off.

Mn-including InAs quantum dots (QDs) were fabricated by Mn-ion implantation and subsequent annealing. The optical, compositional, and structural properties of the treated samples were analyzed by photoluminescence (PL) and microscopy. Energy dispersive X-ray (EDX) results indicate that Mn ions diffused from the bulk GaAs into the InAs QDs during annealing, and the diffusion appears to be driven by the strain in the InAs QDs. The temperature dependence of the PL of Mn-including InAs QD samples exhibits QDs PL characteristics. At the same time, the heavy Mn-including InAs QD samples have ferromagnetic properties and high T-c. (c) 2008 Elsevier B.V. All rights reserved.

The circular photogalvanic effect (CPGE) is observed in InN at inter-band excitation. The function of the CPGE induced current on laser helicity is experimentally demonstrated and illustrated with the microscopic model. A spin-dependent current obtained in InN is one order larger than in the AlGaN/GaN heterostructures at inter-band excitation. The dependence of CPGE current amplitude on light power and incident angle can be well evaluated with phenomenological theory. This sizeable spin-dependent current not only provides an opportunity to realize spin polarized current at room temperature, but also can be utilized as a reliable tool of spin splitting investigation in semiconductors. (c) 2007 Published by Elsevier Ltd.

In this review, the potential of mode-locked lasers based on advanced quantum-dot (QD) active media to generate short optical pulses is analysed. A comprehensive review of experimental and theoretical work on related aspects is provided, including monolithic-cavity mode-locked QD lasers and external-cavity mode-locked QD lasers, as well as mode-locked solid-state and fibre lasers based on QD semiconductor saturable absorber mirrors. Performance comparisons are made for state-of-the-art experiments. Various methods for improving important characteristics of mode-locked pulses such as pulse duration, repetition rate, pulse power, and timing jitter through optimization of device design parameters or mode-locking methods are addressed. In addition, gain switching and self-pulsation of QD lasers are also briefly reviewed, concluding with the summary and prospects.