Abstract

Single-frequency erbium fiber lasers are potentially very attractive, particularly in the telecommunications area, e.g., in dense wavelength-division multiplexed systems where there is a need for large numbers of narrow linewidth sources with accurately determined wavelengths. In this regard, fiber grating-based lasers, such as distributed Bragg reflector¹ (DBR) or distributed feedback^2,3 (DFB) fiber lasers, are especially attractive, as fiber gratings can be made to quite demanding specifications. However, these lasers typically have very short cavities, in order to maintain single-mode operation for the case of DBR lasers, while difficulties in making very long high-quality gratings chiefly constrains the length of DFB lasers, Such short fiber lengths typically lead to inadequate pump power absorption and low laser output powers of ~100 μW.^1,4 One solution put forward to address this problem is the use of phos- phosilicate Er/Yb co-doped fibers, which has been successful in demonstrating efficient DBR laser operation.⁵ However, the low photosensitivity of these fibers makes, it difficult to. write high-quality gratings directly in them, which is essential for DFB fiber laser operation. In this work, we propose and demonstrate another solution to improving the output power/efficiency of short-cavity DBR/ DFB Er³⁺-fiber lasers, which is by intra-cavity pumping in an Yb³⁺ fiber laser cavity.

© 1996 Optical Society of America