Abstract

Abstract
The values of measured and calculated spectroscopic quantities of lithium niobate doped with rare earth and transition metal ions, such as polarized emission and absorption cross sections, variation of fluorescence life time with temperature and concentration of the dopant, Judd-Ofelt coefficients, non-radiative transition probabilities and energy levels are presented. Wherever published data is available, comparison with measured or calculated data presented in this work is carried out. The theories utilized in the interpretation of the experimental results, such as Judd-Ofelt theory, Fuchtbauer-Lademburg relation and McCumber theory are summarily presented.

Abstract

Abstract
Modelling of laser oscillation at 0.9 mu m in Ti waveguides in LiNbO3 doped with Nd ions is presented. Laser emission at 0.9 mu m in Ti waveguides in Nd:LiNbO3 crystals was recently demonstrated. However, lasing was reported as unstable and lasting only a few seconds, with parasitic lasing at the higher gain transition at 1.08 mu m shown to be a problem. In this work the possibility of obtaining efficient and stable laser oscillation at 0.9 mu m in Ti:LiNbO3 waveguides, fabricated in substrates doped with Nd ions by thermal diffusion of thin metallic stripes or planar thin films, was theoretically evaluated. It was concluded that emission at 0.9 mu m, with complete suppression of the parasitic emission at 1.08 mu m, should be possible by selective increase of the losses at 1.08 Irm, through optimization of waveguide and laser cavity, spatial localization of the Nd ions and the use of the dependence on polarization of the emission cross sections at 0.9 and 1.08 mu m.

Abstract

Abstract
Dither demodulation of fiber Bragg grating sensors illuminated with multimode light from laser diodes is theoretically and experimentally investigated. Quasi-static temperature and strain sensitivities of 0.09 degrees C/root Hz and 0.6 mu epsilon/root Hz are obtained. We show that it is possible to measure small ac signals that lie outside the feedback loop bandwidth by using a synchronous detection referenced to twice the dither frequency. In this situation, dynamic strain sensitivity of 3.3 n epsilon/root Hz is achieved. (C) 1999 Optical Society of America.