Efficient operation and characterization of distributed feedback Er/sup 3+/-doped fiber lasers via the 520-nm transition band

Abstract

Single-frequency distributed feedback (DFB) and distributed Bragg reflector (DBR) Er/sup 3+/-fiber lasers are attractive for applications in optical communications and sensor systems. However, as the cavity lengths need to be short (a few cm) for robust single-mode operation, pump absorption is low, limiting laser output powers to <1 mW. Higher laser output powers are desirable. We show that efficient laser operation and high output powers are achievable simply by pumping in the 520-nm transition instead of 980 nm. While 980 nm pumping is conventionally considered to be an excellent choice for erbium-doped fiber amplifiers (EDFAs), this is less clear for erbium-doped fiber lasers (EDFLs). For short-cavity single-frequency EDFLs, the very large absorption cross-section of the 520-nm transition is attractive, as it should enable considerable improvements in the efficiency and output power to be achieved with lasers fabricated in conventional erbium-doped fibers. With compact diode-pumped all-solid-state green sources (e.g., microchip lasers) now commercially available, and rapid progress being made in the field of green laser diodes, this approach to pumping single-frequency DFB and DBR fiber lasers appears promising.