Low-power fault-tolerant laser-to-fiber coupling with photorefractive BaTiO(3).

A novel device for low-power fault-tolerant laser-to-fiber coupling is described; it makes use of self-pumped phase conjugation in photorefractive BaTiO(3). We found the degree of fault tolerance to improve by 2 orders of magnitude to 0.02 dB per 100-mum displacement within the determined displacement range at intensities incident on the crystal as low as 2 mW, compared with the losses without the BaTiO(3) present.

Effects of process errors on the diffraction characteristics of binary dielectric gratings.

The effects of fabrication errors on the predicted performance of surface-relief phase gratings are analyzed with a rigorous vector diffraction technique. For binary elements, errors in the dimensions of the profile [depth, linewidth (fill factor), and grating period], as well as errors in the shape of the profile, are investigated. It is shown that the dimension errors do not have a significant effect on grating performance when the grating is designed for either maximum or minimum diffraction efficiency. A trapezoid is used to model the shape error of the profile. For the first time, design rules that significantly reduce the effects of any shape error are presented.