Comparison between Double Crystals X-ray Diffraction and Micro-Raman Measurement on Composition Determination of High Ge Content Si_(1-x)Ge_(x) Layer Epitaxied on Si Substrate

It is important to acquire the composition of Si1-xGex layer, especially that with high Ge content, epitaxied on Si substrate. Two nondestructive examination methods, double crystals X-ray diffraction （DCXRD） and micro-Raman measurement, were introduced comparatively to determine x value in Si1-xGex layer, which show that while the two methods are consistent with each other when x is low, the results obtained from double crystals X-ray diffraction are not credible due to the large strain relaxation occurring in Si1-xGex layers when Ge content is higher than about 20%. Micro-Raman measurement is more appropriate for determining high Ge content than DCXRD.

Growth of Yb∶YAB Crystal and Its Laser Performance

Single crystal of Yb x Y 1- x Al 3(BO 3) 4 (Yb∶YAB) was grown by using flux method based on the potassium trimolybdate. 160 mW efficient continuous wave green output was obtained from a fibre coupled 976 nm laser diode. The conversion efficiency is larger than 11 3%, and the electrical input green conversion efficiency is 3 9%. Tunable green output from 513 0 to 545 8 nm is also demonstrated with a quartz birefringent filter. By enhancing the incident pump power, 1 1 W cw green output can be reached.

Nd∶ReCOB晶体的生长、各向异性和最佳相位匹配方向

Red,blue and green visible lasers are more attractive with the development of the science and technology.Self frequency doubling is an important approach to realize visible lasers.For self frequency doubling,the basic requests are high figure of merit(FOM),high damage threshold,good chemical stability and mechanical properties.Perfection and growth characters are also important for a practical SFD crystal. In recent years,the discovery of rare earth calcium oxyborates has resulted in the renewal in the field of SFD crystal.ReCaO(BO 3) 3(ReCOB)is a new type of novel nonlinear optical crystals which is nearly congruently melt and can be grown with Czochralski method.ReCOB crystals possess high nonlinear coefficients and damage thresholds.They are non hydroscopic and easy cutting and polishing.They belong to monoclinic with point group m and space group cm.The strong anisotropy originated from the low symmetry makes the measurement and application of the crystal more complicated.More than half of naturally existed crystals belongs to low symmetry,consequently,the research on the nonlinear and anisotropic laser optical properties are not only important for ReCOB crystal,but also useful for the applications of other low symmetry crystals.

Double Q-switched 946 nm laser with MgO：LN electro-optic crystal and MoSe2 saturable absorber

We report a double Q-switched 946 nm laser with a magnesium-oxide-doped LiNbO3 （MgO：LN） electro-optic （EO） crystal and a monolayer molybdenum diselenide （MoSe2） saturable absorber （SA）. A pulsed laser diode side-pumped long neodymium-doped yttrium aluminum garnet rod （φ3×65 mm） is used as the gain medium. Large pulse energy up to 3.15 mJ and peak power up to 346 kW are generated at the repetition rate of 550 Hz, corresponding to the beam quality factors of Mx^2=3.849, My^2=3.868. Monolayer MoSe2 nanosheets applied in the experiment would be a promising SA for a passive Q-switching operation.

Improved optical performance of GaN grown on pattered sapphire substrate

An improved GaN film with low dislocation density was grown on a C-face patterned sapphire substrate （PSS） by metalorganic chemical vapor deposition （MOCVD）. The vapor phase epitaxy starts from the regions with no etched pits and then spreads laterally to form a continuous GaN film. The properties of the GaN film have been investigated by double crystal X-ray diffraction （DCXRD）, atomic force microscopy （AFM） and photoluminescence （PL）, respectively. The full-width at half-maximum （FWHM） of the X-ray diffraction curves （XRCs） for the GaN film grown on PSS in the （0002） plane and the （1012） plane are as low as 312.80 arcsec and 298.08 acrsec, respectively. The root mean square （RMS） of the GaN film grown on PSS is 0.233 nm and the intensity of the PL peak is comparatively strong.