Single-mode behaviour of a multimode 1.55 μm laser with a fibre grating external cavity

Abstract

A 1.55 μm DCPBH multimode laser has been made to oscillate in a single longitudinal mode by feedback from a fibre grating which acts as an external cavity for line narrowing and as a frequency-selective component to give single-mode behaviour. Linewidths of less than 10kHz and side-mode rejection ratios of 320 have been achieved.