Abstract

Abstract
A neodymium-doped glass waveguide laser based on a new structure employing two core layers is reported. This double-layer structure allows a photosensitive layer to be integrated with an efficient gain layer. Singlemode operation was obtained with a lasing threshold of 93 mW and an efficiency of 0.6%.

Abstract
Hybrid materials produced by the hydrolytic sol-gel process reveal strong absorption in the spectral region of 1550 nm, mainly due to the high concentration of OH groups. This characteristic constitutes an obstacle to the application of these materials, in particular to telecom integrated optical devices. A simple thermal treatment applied to the device does not contribute to increase the transparency. The real-time influence of temperature and environment humidity on the optical transmission properties of sot-gel organic-inorganic raised channel waveguides is analyzed in order to achieve an understanding of the OH group's behaviour in the materials. We demonstrate that the level of the optical losses at 1550 nm can significantly be decreased at high temperature. Cooling the sample in dry atmosphere makes it possible to reach a better transparency, which can be useful to improve the performance of hybrid sol-gel optical devices.

Abstract
A comparative analysis on the performance of different scanning regimes in time domain optical coherence tomography is presented in terms of image size. Safety thresholds due to the different continuous irradiation time per transverse pixel in different scanning regimes are also considered. We present the maximum exposure level for a variety of scanning procedures, employing either A scanning (depth priority) or T scanning (transverse priority) when generating cross section images, en face images or collecting 3D volumes. We present a comparison between such B-scan images, and different criteria to allow the user to choose the right mode of operation. Mainly, two criteria are detailed, a scanning criterion and a safety criterion. The scanning criterion depends on the number of pixels along the lateral and axial directions. The analysis shows that en-face scanning allows wider images while the longitudinal scanning is more suitable to deep cross sections. The safety criterion refers to safety levels to be observed in each scanning mode. We show that the flying spot OCT imaging has different safety limits for T- and A- based imaging modes. The analysis leads to maximum permissible optical power levels that favors T-scan imaging of wide objects. We then apply the analysis considering as object the eye.

Abstract
We present the time variant second order statistics of the depth-scan photocurrent in timedomain optical coherence tomography (TD-OCT) systems using polarized thermal light sources. Our results are prerequisite for future development of statistical image processing techniques for TD-OCT. © 2007 Optical Society of America.

Abstract