Tunable laser with partial reflectors

This paper describes the theory, modelling and design of a simple tunable l aser with a 15-20 run quasi-continuous tuning range, 30 dB side mode suppre ssion ratio, 400 kHz linewidth and low variation in output power. Prototype fabrication has used focussed ion beam etching to modify standard Fabry-Pe rot structures. The laser has four electrically isolated sections separated by reflection/scattering sites with power reflectivity of about 1%. Tuning is achieved by changing the currents to each section and hence altering th e refractive indices.