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Vertical cavity surface emitting lasers (VCSELs) have lots of excellent properties, such as circular beam, low threshold, single longitudinal mode, high speed modulation and monolithic array fabrication capability. The VCSELs have been widely used in data communication and short-distance optical interconnection. In the fields of distance detection and automatic driving, high accuracy lidars have become an indispensable component. In practical applications, 905 nm laser exhibits little absorption by the water vapor in the air. In addition, the 905 nm laser can match with both inexpensive Si detector and high response avalanche photodiode (APD). Therefore, the 905 nm semiconductor laser has become a key light source of lidar. This paper presents the design and fabrication of 905 nm VCSEL with high power conversion efficiency. First, the main factors influencing the power conversion efficiency (PCE) of VCSEL are analyzed theoretically. It is concluded that the slope efficiency contributes to the PCE most. In order to achieve a high slope efficiency, strained InGaAs is used as a quantum well material. Due to the wavelength redshift caused by the thermal effect, the lasing peak wavelength of the multiple quantum well (MQW) is designed to be about 892 nm by optimizing the In composition. The active region consists of three pairs of In0.123Ga0.88As/Al0.3Ga0.7 MQWs. The N-distributed Bragg reflectors (DBRs) are designed to have 40 pairs of Al0.9Ga0.1As/Al0.12Ga0.88As, and the P-DBRs are designed to have 20 pairs of Al0.9Ga0.1As/Al0.12Ga0.88As. The epitaxial structure is designed and grown by metal organic chemical vapor deposition (MOCVD). The cavity mode of the epitaxial wafer is around 903.7 nm. The photoluminescence (PL) spectrum is also measured. The peak wavelength is approximately 893.7 nm, and the full width at half maximum is 21.6 nm. Then, the 905 nm VCSELs with different apertures (6–18 μm) are fabricated via semiconductor technologies such as photolithography, evaporation, inductively coupled plasma (ICP), wet oxidation, electroplating, etc. Finally, the L-I-V characteristics and spectra of VCSELs with different apertures are tested. The obtained maximum slope efficiency and PCE of the devices are 1.12 W/A and 44.8%, respectively. In addition, the influences of aperture size on the far-field profiles and spectra of the devices are investigated. These 905 nm VCSELs with high PCE are potential for the miniaturization and lowing the cost of LiDAR.

The procedure of simulating convergent beam electron diffraction (CBED) pattern of quasicrystals by dynamical theory is described. The simulated patterns are generally coincide with the experimental patterns. The variations of intensity distribution in CBED pattern with the amplitude and phase of the structure factor of quasicrystal are calculated with dynamical theory. The sensitivity of intensity distribution to the structure factor is investigated.

TiO2 anatase thin films on quartz substrates were prepared with sol-gel method. The dry gel films, made by spin coating 10 times, were calcined at various temperatures. From X-ray diffraction analyses, it is found that the anatase to rutile phase transformation temperature of the films is higher than 850°C, the films are preferentially oriented on (0 0 1) plane, i. e.c-axis oriented. The thickness, refractive indexes, absorption coefficients and extinction coefficients of the films were determined from UV-Vis transmission spectra of the films using a UV-Vis spectrophotometer. The thickness of the films is about 570 nm. The refractive indexes, absorption coefficients and the extinction coefficients of the present films are larger than the values of anatase films prepared by sputtering. This indicates that the films made with sol-gel method are very dense.

We report measurements of the neutral and charged particle fractions produced by running beams of Li−, C−, O−, and Si− at energies up to 7 MeV through gas cells of N2, Ar, or CO2. We discuss the implications of these measurements for the design of neutralizers to produce high‐energy light atom beams for heating or current drive in tokamaks.

The impact-parameter dependence of the quasimolecular $K$ x rays emitted in collisions of 10-MeV ${\mathrm{Cl}}^{16+}$ with Ar has been measured. The coincidence spectra show a clear impact-parameter-dependent structure. The results are in good agreement with dynamical calculations which take into account the interference between the $1s\ensuremath{\sigma}$ decay amplitudes in the incoming and the outgoing halves of the trajectory.

The present status of the production of low-energy highly ionized beams by the 4-stage tandem accel-decel method is surveyed, and their use in three atomic physics experiments is summarized. The experiments are: the measurement of the charge state dependence of K-X-ray production in S+q-Ar collisions at 10 MeV, the impact-parameter dependence of quasimolecular X-rays in S+15-Ar collisions again at 10 MeV, and the determination of charge transfer cross section in S+q + Ar, He collisions. The results of the three experiments give evidence that the 4-stage accel-decel ion production technique is extremely powerful and useful.

K-x-ray production cross sections have been measured in (nearly symmetric) $_{16}$S${+\mathrm{}}_{18}$Ar and (very asymmetric) $_{16}$S${+\mathrm{}}_{2}$He collisions as a function of the projectile charge state q (q=3--16) at low incident energies of 10 and 20 MeV. The charge-state dependence is very similar in the two cases, confirming results obtained at higher incident energies. The sensitivity of such studies to different K-vacancy-production mechanisms is discussed.