Tuning characteristics of an external cavity semiconductor laser

Tuning properties of a 1.3 μm external AR-coated semiconductor laser (ECL) with grating feedback and a cavity length of approximately 40 mm have been investigated. The measured threshold current, Lorentzian linewidth and output power have been compared with theoretical simulations based on an optical transmission line model, which is capable of handling strong and frequency selective optical feedback in semiconductor lasers. An analysis technique to determine the Lorentzian linewidth in the presence of Gaussian linewidth broadening is presented. The Lorentzian linewidth can consistently be determined within 10% independent of the length of the delay fibre