Xiaoyu Ma

2-ps passively mode-locked Nd:YVO4 laser using an output-coupling-type semiconductor saturable absorber mirror

We have demonstrated stable self-starting passive mode-locking in a diode-end-pumped Nd: YVO4 laser using a semiconductor saturable absorber mirror (SESAM). An ln(0.25)Ga(0.75)As single quantum-well SESAM, which was grown by the metalorganic chemical-vapor deposition technique at low temperature, acts as a passive mode-locking device and an output coupler at the same time. Continuous-wave mode-locked transform-limited pulses were obtained at 1064 nm with a pulse duration of 2.1 ps and an average output power of 1.28 W at a repetition rate of 96.5 MHz. (c) 2005 American Institute of Physics.

Diode-End-Pumped Passively CW Mode-Locked Nd:YLF Laser by the LT-In

We have demonstrated a self-staring passively continuous-wave mode-locked diode end-pumped Nd:YLF laser with a semiconductor saturable absorber mirror of single-quantum-well (In0.25Ga0.75 As) grown by metal-organic chemical-vapor deposition technique at low temperature. The saturable absorber was used as nonlinear absorber and output coupler simultaneously. Stable pulse duration of 3 ps has been achieved at the repetition rate of 98 MHz. The average output power was 530 mW at 1053 nm under the incident pump power of 10 W, corresponding to the peak power of 1.8 kW and pulse energy of 5.4 nJ

_0.25

Tunnel-regenerated multiple-active-region (TRMAR) light-emitting diodes (LEDs) with high quantum efficiency and high brightness have been proposed and fabricated. We have proved experimentally that the efficiency of the electrical luminescence and the on-axis luminous intensity of such TRMAR LEDs scaled linearly approximately with the number of the active regions. The on-axis luminous intensity of such TRMAR LEDs with only 3 mum GaP current spreading layer have exceeded 5 cd at 20 mA dc operation under 15 degrees package. The high-quantum-efficiency and high-brightness LEDs under the low injection level were realized

Ga

The growth and magnetism of Fe thin films on the GaN(0001) surface are studied by scanning tunneling microscopy and surface magneto-optic Kerr effect. It is found that Fe grows in a layer-by-layer mode on the pseudo-1×1 surface at room temperature, and the film develops magnetism at 1.2 ML and shows perpendicular magnetic anisotropy below 6 ML. On the bulk-terminated 1×1 surface, Fe grows in a three-dimensional mode, and ferromagnetization with in-plane anisotropy is observed only above 4.3 ML. Fe-induced √7×√7 reconstruction on the pseudo-1×1 surface plays the key role in reducing the interface reaction and promoting the two-dimensional growth.

_0.75

Surface structure of the Sn islands 5 ML high, prepared on Si(111)-(2 root 3X2 root 3)-Sn substrate, is investigated by low temperature scanning tunneling microscopy/spectroscopy. Due to the elastic strain relaxation in the islands, the in-plane unit cell structure distorts and the apparent height of the surface atoms varies regularly to form an overall modulated strip structure. The quantum well states are observed to depend on the relative position within this structure, which implies the change of the surface chemical potential induced by the elastic strain relaxation as well.

As Absorber

The problem of conventional light emitting diodes (LEDs) was analyzed. A novel tunnel-regenerated multiple-active-region light-emitting diode with high quantum efficiency and high brightness has been proposed and fabricated. We have proved theoretically that the efficiency of the electrical luminescence and the on-axis luminous intensity of such novel LEDs scaled linearly approximately with the number of the active regions. The on-axis luminous intensity of such novel LED with only 3 /spl mu/m GaP current spreading layer has exceeded 5cd at 20 mA DC operation under 15/spl deg/ package. The ultrahigh quantum efficiency and ultrahigh brightness LED under the low injection level was realized.