Abstract

Recently there has been a renewal of interest in the use of fibers doped with optically active ions, principally rare earths, as active devices in optical fiber communications and sensor systems. This increase in activity has been driven by improved methods for incorporating dopants into telecommunications-grade fiber, the availability of laser pumps, and the requirements of advanced fiber-optic systems. Single-mode silica fiber lasers, optical amplifiers, and superluminescent devices exhibiting exceptional performance have been demonstrated at many laboratories. Results have included laser thresholds of <100 µV, slope efficiencies of >50%, and tuning ranges exceeding 70 nm. Q-switched and single-frequency operation have been achieved, the latter with linewidths of ≤1 MHz. Both Nd³⁺ and Er³⁺ have been pumped by 0.8-µm diode lasers; the all-fiber mirrors and ring lasers have been demonstrated. Optical amplifiers have produced gains of >30 dB at 1.55 µm and appear to have good noise properties, while superluminescent single-mode fibers have generated powers of > 10 mW at 1.06 µm. Major issues limiting performance include excited-state absorption, which Inhibits gain for Nd³⁺ at 1.3 µm and reduces the pumping efficiency for Er³⁺ as well as the peak gain vs optical bandwidth trade-offs.

© 1988 Optical Society of America