Compressively Strained InGaAs/InGaAsP Quantum Well Distributed Feedback Laser at 1.74μm

The compressively strained InGaAs/InGaAsP quantum well distributed feedback laser with ridge-wave- guide is fabricated at 1.74μm. It is grown by low-pressure metal organic chemical vapor deposition（MOCVD）. A strain buffer layer is used to avoid indium segregation. The threshold current of the device uncoated with length of 300μm is 11.5mA. The maximum output power is 14mW at 100mA. A side mode suppression ratio of 35.5dB is obtained.

Simulation and prediction in laser bending of silicon sheet

The laser bending of single-crystal silicon sheet （0.2 mm in thickness） was investigated with JK701 Nd：YAG laser. The models were developed to describe the beam characteristics of pulsed laser. In order to simulate the process of laser bending, the FEM software ANSYS was used to predict the heat temperature and stress-strain fields. The periodic transformation of temperature field and stress-strain distribution was analyzed during pulsed laser scanning silicon sheet. The results indicate that the mechanism of pulsed laser bending silicon is a hybrid mechanism in silicon bending, rather than a simple mechanism of TGM or BM. This work also gets silicon sheet bent after scanning 6 times with pulsed laser, and its bending angle is up to 6.5°. The simulation and prediction results reach well agreement with the verifying experiments.

Comparison of stress distribution of thoracolumbar vertebrae under forces with CT value

To provide a new method to estimate the effectiveness of thoracolumbar vertebral finite element model. Methods: A mechanical model of human thoracolumbar vertebrae motion segment was made using three-dimensional finite element method and the stress distribution of vertically compressed thoracolumbar vertebrae was analyzed, meanwhile, 20 patients with burst fracture of thoracolumbar vertebrae were tested by CT to calculated average CT value at ascertained different points of thoracolumbar vertebrae. The calculated results and effective stress at the same position were analyzed with straight line correlation. Results: The stress level of different position of thoracolumbar vertebrae under vertical compressive force was positively correlated with the correlative CT value, and the regressive style, Y= 214.028 + 45.268 X, r= 0.7386 , P< 0.05 (n=8) showed a statistical significance.Conclusions: To study mechanism of thoracolumbar vertebrae injuries under different forces has clinical significance.

Formation and strain distribution of Ni/NiO core/shell magnetic nanoparticles fabricated by pulsed laser deposition

Nucleation and growth lead to substantial strain in nanoparticles embedded in a host matrix. The distribution of strain field plays an important role in the physical properties of nanoparticles. Magnetic Ni/NiO core/shell nanoparticles embedded in the amorphous Al2O3 matrix were fabricated by pulsed laser deposition. The results from a high-resolution transmission electron microscope also revealed that the core/shell nanoparticles consist of a single crystal Ni core with a faced-centered cubic struc- ture （Space Group FM-3M） and polycrystalline Nit shell with a trigonal/rhombohedral structure （Space Group R-3mH）. The growth strain of Ni/NiO core/shell nanoparticles embedded in the Al2O3 matrix was investigated. Finite element calculations clearly indicate that the Nit shell incurs large compressive strain. The compressive strain existing at the Nit shell area ena- bles the shell material at the interface to adapt to the lattice parameters of Ni core. This process results in a relatively good crystallinity near the interface, which may be associated with the higher exchange coupling between the ferromagnetic Ni core and antiferromagnetic Nit shell.