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Three-dimensional topological insulators are a new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface. By investigating the surface state of [Bi.sub.2][Te.sub.3] with angle-resolved photoemission spectroscopy, we demonstrate that the surface state consists of a single nondegenerate Dirac cone. Furthermore, with appropriate hole doping, the Fermi level can be tuned to intersect only the surface states, indicating a full energy gap for the bulk states. Our results establish that [Bi.sub.2][Te.sub.3] is a simple model system for the three-dimensional topological insulator with a single Dirac cone on the surface. The large bulk gap of [Bi.sub.2][Te.sub.3] also points to promising potential for high-temperature spintronics applications.

Measurements for photorefractive dynamic properties under polarized light with different luminous intensity and wavelength at 650 nm were performed in calcium-doped strontium barium niobate crystals as a function of the time. Experimental results further validated that the different input luminous intensities influence only the saturated time and photorefractive velocity of the photorefractive crystals. Birefringence experiments suggest that an input luminous intensity oscillatory threshold should exist between 64 mW/[cm.sup.2] and 13 mW/[cm.sup.2]. The dynamic change of refractive index from self-focusing to asymmetric self-defocusing was also measured and regarded as the mutual results of the nonuniform-intensity incidence and positive thermal lens effect, which was validated by a further experiment based on the Michelson interference. Also, oscillation accompanying change in the dynamic indices was analyzed and attributed to the high dielectric effect as well as asymmetric self-defocusing in this investigation. OCIS codes: 160.5320, 260.1440, 190.0190.

A diode-pumped Yb:YCOB laser at 1086 nm is passively Q switched by using InGaAs quantum wells as saturable absorbers and utilizing the Bragg mirror structure as an output coupler. With an absorbed pump power of 9.2 W the laser produces pulses of 100 ms duration with average pulse energy of as much as 165 [micro]J at a pulse repetition rate of 7 kHz. OCIS codes: 140.0140, 140.3540, 140.3580.

Vortices shed from the tip of a rectangular half-span wing model (NACA 0012) have been investigated with particle image velocimetry at a chord Reynolds number between 3.4 x [10.sup.4] and 26.6 x [10.sup.4] and angles of attack [alpha] = 8 and 16 deg over 0.2 ~ 5 chord lengths downstream of the model. It has been found that the measured wing-tip vortex shows little dependence in the circumferential velocity [v.sub.[theta]] and vorticity [OMEGA], when normalized by their local maximum, on [alpha], Reynolds number, and downstream distance from the wing. Furthermore, the radial distributions of [v.sub.[theta]] and [OMEGA] coincide quite well with the exponential vortex solution, with only a slight departure outside the core region.

A modified Czochralski technique was used to grow Nd-doped yttrium orthovanadate crystals.

Several studies are conducted to explain the synthesis, as well as the thermal properties of the disordered Nd-doped SrGd[Ga.sub.3][O.sub.7] laser crystal grown by the Czochralski method. The crystal is shown to demonstrate a glasslike behavior, as an increase in the temperature is shown to lead to a significant enhancement in its thermal conductivity.

Several studies are conducted to explain the preparation, as well as the different electromechanical and electro-optic properties of the tungsten bronze [([Ca.sub.0.28][Ba.sub.0.72]).sub.0.25][([Sr.sub.0.6][Ba.sub.0.4]).sub.0.75][Nb.sub.2][O.sub.6] single crystal.

A Czochralski method was used to fabricate and characterize Nd-doped calcium barium niobate (Nd:CBN-28) single crystal. The results obtained helped to calculate the thermal conductivity of the crystal and estimated the phonon mean free path along the a- and c-axes of Nd:CBN-28 crystal.

Cubic potassium tantalite niobate [K[Ta.sub.1-x][Nb.sub.x][O.sub.3] (KTN)] crystals of large size, good quality and varying Nb concentration are grown by the Czochralski method and their thermal properties are studied. The results have shown that crystalline KTN is a very good material for optical applications.

The synthesis, characterization, and the thermal properties of the mixed Nd:[Lu.sub.x][Gd.sub.1-x]V[O.sub.4] laser crystals are discussed. The observed mixed crystals are found to act as excellent laser materials and hence can be used in the Q-switched laser operation.

The stimulated emission cross section is given based on the quantum electrodynamics and by using Einstein's coefficient and Planck's energy density. The measured absorption of 0.5 at. percent Nd-doped Nd:GdVO4 crystal was compared to the Judd-Ofelt (JO) theory.