A three-dimensional (3-D) imaging configuration with a holographic scanner and two auxiliary reflectors is discussed, which employs a Nd:YAG laser that operates at a wavelength of 1.06 μm. Compared with traditional scanners, holographic scanner has many advantages, such as smaller in size, lighter in weight and simpler in structure. The data collected are stored into a 3-D array of 8-bit intensity values and displayed in two ways, a 2-D intensity image or a 3-D image. The 3-D image is displayed on the screen of a computer according to the perspective transformation technology of coordinates.
Er<sup>3+</sup>/Yb<sup>3+</sup>co-doped tantalum-phosphate glass was prepared. Compared with the conventional phosphate glasses, the tantalum-phosphate glass posses higher glass transition temperature, and then chemical durability. Based on the measured absorption spectra, the absorption and emission cross sections for <sup>4</sup>I<sub>13/2</sub> -> <sup>4</sup>I<sub>15/2</sub> transition and some important radiative properties of Er<sup>3+</sup> were calculated and discussed by using McCumber theory and Judd-Ofelt theory. The results show the peak values and effective bandwidth of emission cross section are larger and wider. These properties make Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped tantalum-phosphate glass much more attractive candidates for microchip lasers and integrated optical amplifiers.
The spectral properties of Er<sup>3+</sup>-doped tellurite glasses whose compositions are 40TeO<sub>2</sub>-40WO<sub>3</sub>-10ZnO-10Na<sub>2</sub>O and 40TeO<sub>2</sub>-40WO<sub>3</sub>-10 PbCl<sub>2</sub>-10Na<sub>2</sub>O were measured and analyzed by using Judd-Ofelt and McCumber theories. Compared with traditional tellurite glasses, these glasses have more stable thermal properties and the emission spectra and emission cross sections at the 1.53 m band are larger and broader. Based on the measured absorption spectra, the spontaneous transition probabilities, the fluorescence branching ratios and the radiative lifetimes of these glasses were also calculated.
The niobate-phosphate glasses with high Er<sup>3+</sup>/Yb<sup>3+</sup> concentration were prepared. The absorption and fluorescence emission spectra were measured. The effect of Er<sup>3+</sup>/Yb<sup>3+</sup> ion concentrations on the spectroscopic properties was researched. The emission cross sections for <sup>4</sup>I<sub>13/2</sub> <sup>4</sup>I<sub>15/2</sub> transition of Er<sup>3+</sup> was calculated by McCumber theory. It was found that the emission cross sections around 1534nm increase and then decrease with the increase of rare earth ion concentrations. The maximum intensity of fluorescence occurs at the concentration of 6wt%. The effective emission cross section bandwidth was also discussed.
In this paper a high accuracy heterodyne interferorneter measuring absolute distance is proposed. The triangular current is applied to the laser diode and frequency shift is performed using Bragg Cell and two-modulation is achieved. A high frequency clock for the phase measurement is employed. The system has high accuracy and high sensitivity.