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An Fe–19Cr–0.6Al–12Mn duplex stainless steel with an optimized alloy composition of Ni replaced by Mn and Cr partially replaced by Al was developed to avoid the edge cracking, which is a common defect in the hot rolling of traditional two-phase stainless steels. The newly developed duplex stainless steel could be hot-rolled in the single-phase ferrite (α) region by controlling rolling temperature and the single-phase ferrite microstructure was retained on water cooling. To obtain the two-phase stainless steel product with ferrite and austenite (γ) microstructure, cold rolling and annealing were carried out, and appropriate cold rolling reduction and annealing process parameters were determined. The significant impact of annealing on microstructure, mechanical properties and pitting resistance of the experimental steel was studied. It was observed that with the increase in cold rolling reduction, the number of γ nucleation points was dramatically increased leading to the precipitation of more γ at α grain boundaries after annealing. During annealing at 800 °C and with the increase in annealing time, the austenite fraction was increased with a lower rate and remained almost constant when the annealing time was greater than 4 h. With the increase in annealing temperature, the austenite fraction decreased gradually in the temperature range of 750–860 °C. Good combination of strength, ductility and excellent pitting resistance was obtained by cold rolling to 80% reduction and annealing at 800 °C for 4 h. Grain refinement and the existence of Σ3 boundaries played a vital role in improving the pitting resistance of the experimental steel. With good combination of strength, ductility and corrosion resistance, the newly developed duplex stainless steel is expected to be a new resource-saving dual-phase stainless steel.

The sacrificed-QD-layer method can well control the indium deposition amount to grow InAs quantum dots (QDs) with isotropic geometry. Individual Si dopant above an (001)-based InAs QD proves a new method to build a local electric field to reduce fine structure splitting (FSS = X1−X2) and show D3h symmetric excitons. The lowest FSS obtained is 3.9 μeV with the lowest energy X state (LX) anticlockwise rotate from [1–10] (i.e., zero FSS will be crossed in a proper field). The lateral field projection induces a large eh separation and various FSS, LX, and emission intensity polarization. The lateral field along [1–10] breaks the X1–X2 wavefunction degeneracy for independent HH and VV cascade emissions with robust polarization correlation. With FSS ~4 μeV and T1 ~0.3 ns fastened in a distributed Bragg reflector cavity, polarization-resolved XX–X cross-correlations show fidelity ~0.55 to a maximal entangled state |HH> + |VV>. A higher fidelity and zero FSS will be obtained in the hybrid QD structure with a junction field integrated to tune the FSS and a sub-bandgap excitation to avoid influences from electrons in the barrier.

In the local droplet etching (LDE) method, the fine split structure (FSS) of quantum dots (QDs) is directly related to the shape of the nanopores formed after annealing. The formation of highly symmetrical nanoporous is the key to the preparation of GaAs/AlGaAs QDs with small FSS. The measurement and characterization of the nano pore shape before and after annealing showed that the density of the nano pore contours is different in different directions, indicating that the slope of the sidewall of the nano pore is different. Therefore, the QDs formed by LDE still have FSS. It has also been observed in experiments that one of the reasons for the asymmetry of the nanoporous is that the etching points covered by the Al droplets on the AlGaAs surface are not in the center of the droplets, which is caused by the supersaturation and maturation of Al atoms during the formation of the droplets. The asymmetry of the annular wall of the nano pore will cause the increase of the FSS of the QDs in the shallow nano pore. When the nano pore is deep enough, the influence of the annular wall of the nano pore on the QDs can be completely ignored, which greatly simplifies the preparation of nano pore. It has certain guiding significance of the preparation of nanoporous required for the growth of QDs with small FSS.

Uniform arrays of three shapes (gauss, hat, and peak) of GaAs microlenses (MLs) by wet-etching are demonstrated, ∼200 nm spatial isolation of epitaxial single QDs embedded (λ: 890–990 nm) and broadband (Δλ∼80 nm) enhancement of their quantum light extraction are obtained, which is also suitable for telecom-band epitaxial QDs. Combined with the bottom distributed Bragg reflector, the hat-shaped ML forms a cavity and achieves the best enhancement: extraction efficiency of 26%, Purcell factor of 2 and single-photon count rate of 7×106 counts per second at the first lens; while the gauss-shaped ML shows a broader band (e.g., longer λ) enhancement. In the MLs, single QDs with featured exciton emissions are observed, whose time correlations prove single-photon emission with multi-photon probability g(2)(0)=0.02; some QDs show both biexciton XX and exciton X emissions and exhibit a perfect cascade feature. This work could pave a step towards a scalable array of QD single-photon sources and the application of QD photon-pair emission for entanglement experiments.

We report on successful fabrication of GaSb-based type-I quantum well distributed Bragg reflector (DBR) lasers emitting around 2.3μm. Second-order Bragg gratings of chromium were patterned by electron beam lithography. For 1.5-mm-long laser diode, single mode continuous-wave operation with output power of 10mW is obtained. The devices show a stable single mode operation with high side mode suppression ratio.

We proposed a precise calibration process of Al 0.9Ga0.1As/GaAs DBR micropillar cavity to match the single InAs/GaAs quantum dot (QD) exciton emission and achieve cavity mode resonance and a great enhancement of QD photoluminescence (PL) intensity. Light-matter interaction of single QD in DBR micropillar cavity (Q ∼ 3800) under weak coupling regime was investigated by temperature-tuned PL spectra; a pronounced enhancement (14.6-fold) of QD exciton emission was observed on resonance. The second-order autocorrelation measurement shows g(2)(0)=0.070, and the estimated net count rate before the first objective lens reaches 1.6×107 counts/s under continuous wave excitation, indicating highly pure single-photon emission at high count rates.

Here we report the growth method of InGa/GaAs quantum dot (QD) with differnet QD density by manipulating InAs deposition rate from 0.065 ML/s to 0.1 ML/s. Chose the highest density QD as the active region and grow multilayer InAs/GaAs QD with high uniform. Then fabricate a narrow ridge waveguide laser by semiconductor process. The rigid waveguide is 1.8 um high and 5 um wide, and the cavity length is 1mm. The output power of this narrow-rigid laser is 164 mW and central wavelength is 1204.6 nm when the injection current is 0.5 A at 15°C. The threshold current is as low as 35 mA, and threshold current density is 1939 A/cm2.

Here we report the solid source molecular beam epitaxy (MBE) growth of high quality of InGaAs/ GaAs quantum dot (QD) structures. A laser device is fabricated by the semiconductor process, including Lithography, Inductively Coupled Plasma (ICP), Plasma Enhanced Chemical Vapor Deposition (PECVD) and Reactive Ion Etching (RIE). The rigid is 100μm wide and cavity is 2000um long. Room temperature continuous-wave (CW) operation with emission wavelength around 1.31μm is presented. Threshold current (Ith) and threshold current density (Jth) is 0.3A and 150A/cm2 at 15°, and output power at Ith=7A reached as high as 1.079W. We also observe that the spectrum shift from 1315nm to 1333nm when the injection currents increase from 1.5A to 3.5A, and the shift speed is 8.72 nm/A.

Fe–Mn–Si bearing shape memory alloys are used as structural and functional materials, and have the potential for application in industrial and architectural fields. Fe–Mn–Si–Cr–Ni based shape memory alloys were selected to elucidate the impact of C and Si content on shape memory effect, where Si was replaced by Co. In this regard, Fe–15Mn–5Si–8Cr–5Ni, Fe–15Mn–5Si–8Cr–5Ni-0.1C, and Fe–15Mn–3Si–8Cr–5Ni-0.1C–2Co alloys were designed to simultaneously elucidate the shape memory effect (SME) and mechanical properties in relation to the microstructure. The study indicated that the addition of 0.1 wt% C significantly improved the SME of Fe–Mn–Si–Cr–Ni alloy, and the shape recovery rate of Fe–15Mn–5Si–8Cr–5Ni-0.1C alloy aged at 750 °C for 4 h was maximum at 55.45%. The content of thermally-induced martensite was reduced, which led to decrease in the probability of α′-martensite formation, and promoted inverse transformation of stress-induced martensite and enhanced the shape memory effect. In addition, the strength of the parent phase was enhanced by segregation of elements during aging. Furthermore, the plastic deformation involving slip during stress-induced martensitic transformation was reduced. The reduced content of α′-martensite promoted reversal of stress-induced martensite. On the other hand, Co increased the stacking fault energy and reduced nucleation of stress-induced martensite, such that the number density of stacking faults decreased the shape memory effect of the experimental steel.

Edge cracking phenomenon occurs in ‘Mn + N′ duplex stainless steels because of inferior thermoplasticity that is mainly induced by the non-uniform deformation between ferrite and austenite phase with different strength during hot rolling, limiting its application. To address this problem, a Fe–19Cr-0.6Al–1Ni–12Mn duplex stainless steel with an optimized alloy composition was trial-prepared, where Ni is substituted by Mn and Cr is partially substituted by Al. This enabled a high content ferrite to be present during hot rolling to reduce the adverse effect of austenite on thermoplasticity. Thus, the edge cracking of hot rolled plates was solved. Furthermore, the formation of austenite was governed by annealing after cold rolling. In view of this, it is significant to study phase transformation and precipitation in duplex stainless steel during annealing. A large number of experimental results indicated that there were two types of transformation during the annealing process: the transformation of ferrite to austenite and recovery and recrystallization of ferrite. After annealing at lower temperature, the austenite was characterized by the banded structure at the grain boundaries of ferrite. Besides, the formation of austenite restricted recrystallization of ferrite. With the increase of annealing temperature, the growth of austenite grain would be enhanced, and the banded austenite evolved into bamboo morphology or island morphology. When the annealing temperature was greater than 900 °C, recrystallization of ferrite was promoted, and transformation of ferrite to austenite was inhibited. However, the precipitation of σ phase increased with the decrease of annealing temperature below 800 °C, reducing plasticity and pitting resistance for the investigated steel.

The device characteristics of semiconductor quantum dot lasers have been improved with progress in active layer structures. Self-assembly formed InAs quantum dots grown on GaAs had been intensively promoted in order to achieve quantum dot lasers with superior device performances. In the process of growing high-density InAs/GaAs quantum dots, bimodal size occurs due to large mismatch and other factors. The bimodal size in the InAs/GaAs quantum dot system is eliminated by the method of high-temperature annealing and optimized the in situ annealing temperature. The annealing temperature is taken as the key optimization parameters, and the optimal annealing temperature of 680 °C was obtained. In this process, quantum dot growth temperature, InAs deposition, and arsenic (As) pressure are optimized to improve quantum dot quality and emission wavelength. A 1.3-μm high-performance F-P quantum dot laser with a threshold current density of 110 A/cm2 was demonstrated.