Abstract

Recently, diode laser-pumped operation of the 1.5-µm transition in Er³⁺-doped silica fibers has been reported.^1,2 The limited pump power available from the single stripe sources used in those experiments restricted the maximum output powers to below 200 µW and slope efficiencies to a few percent. Using a diode array pump source, we achieved output powers in excess of 5 mW at 15 % slope efficiency. A Spectra Diode Laboratories SDL 2432 ten-element diode array was placed in an external cavity to improve spatial coherence of the array output and allow efficient coupling into the fibers used here. Typical launched powers were 50-70 mW at 806 nm for an array drive current of 500 mA. At these pump levels, a small-signal absorption of ~15 dB at the pump wavelength, and ~50% output coupling, is found experimentally to yield maximum efficiencies at a lasing wavelength near 1.56 μm. This is consistent with a numerical model of a longitudinally pumped three-level laser, which includes excited state absorption.

© 1988 Optical Society of America