The increasing demand for high bit-rate telecommunication links is met by transmitting data at several wavelengths simultaneously through a single optical fiber. To add and separate these different wavelengths, special wavelength selective elements are required. The rapidly increasing demand for highly wavelength selective elements can be met by inducing Bragg gratings directly in the core of optical waveguides using UV light at a wavelength around 248 nm and a diffractive optical element called a phase mask. The goal of this research project is to implement an advanced UV writing facility which can induce almost any given index modulation in a waveguide structure with the aid of highly accurate computer controlled translation stages. The first part of the project including characterization of the index change versus fluence showed very promising results. To control the translation stages and the different UV laser sources an advanced software package is currently being developed. It includes algorithms based on a phenomenological model developed at MIC to translate a desired index profile into a UV light fluence profile. In 1998 we have also carried out a thorough investigation of the nature of the single mode laser output of distributed feedback (DFB) fiber lasers developed earlier in the project. We find that the birefringence of the UV induced phase-shift is responsible for the extremely stable single polarization-mode output of the laser. Progress in the active waveguide program enabled demonstration of planar germanosilicate distributed Bragg reflector (DBR) lasers. In this project the mirrors were UV induced directly in a planar erbium doped waveguide. By shifting the maximum wavelength of reflection between the two gratings in the laser resonator, mode selection was obtained leading to stable single mode laser output.
|Period||01/01/95 → 31/12/99|