A LASER AND AN AMPLIFIER

摘要

An 850 nm laser and/or amplifier comprises a single mode fluoro-zirconate optical fibre (20) doped with Er<3+>. CW operation of the normally self-terminating lasing transition <4>S3/2 to <4>I13/2 is achieved by applying excitation energy at 801 nm which both maintains a population inversion between the lasing levels and also populates the upper lasing level by a two-stage process of excitation to the <4>I9/2 level from the <4>I15/2 ground state and then to <2>H9/2 level by ESA.