DESIGN OF WIDELY TUNABLE SEMICONDUCTOR-LASERS USING GRATING-ASSISTED CODIRECTIONAL-COUPLER FILTERS

The analysis and design of widely tunable semiconductor lasers using g rating-assisted codirectional-coupler filtering in a vertical twin-gui de structure are considered. An orthogonal coupled mode formalism is a pplied to obtain the important design parameters for the filter. It is shown that there is a tradeoff between tuning range and spectral puri ty when using this type of filter as an intracavity mode selector. Pra ctical laser structures are presented and design considerations and li mitations are discussed with examples in both GaAs and InP material sy stems having lasing wavelengths around 0.98 and 1.55 mum, respectively .