Mode-locked operation of a figure-of-eight erbium-doped fiber laser based on a 3-/spl times/-3 non-linear loop mirror

Abstract

Summary form only given. The non-linear amplifying loop mirror (NALM) has many varied applications and one of the key ones is that of a saturable absorber. In fact NALMs have been used to induce short pulse formation from a range of fiber lasers with different rare earth dopants. The most common format for the non-linear loop mirror is based on a 2-x-2 coupler, with a symmetric coupling ratio, and an optical amplifier, which is placed asymmetrically, in the loop. We describe a novel variation of the NALM structure whereby the 2-x-2 coupler is replaced by a 3-x-3 coupler. We present the results from numerical modelling that describe the switching characteristics of the 3-x-3 NALM and compare them to those of a standard 2-x-2 NALM. We also describe the data from experimental studies, which show that it is possible to mode-lock an erbium-doped fiber laser with the 3-x-3 NALM. We compare and contrast the mode-locked performance of a 3-x-3 system with that of the 2-x-2 system and explain the origin of the differences in behaviour between the two systems.