Discretely Tunable Semiconductor Lasers Suitable for Photonic Integration

A sequence of partially reflective slots etched into an active ridge waveguide of a 1.5 mum laser structure is found to provide sufficient reflection for lasing. Mirrors based on these reflectors have strong spectral dependence. Two such active mirrors together with an active central section are combined in a Vernier configuration to demonstrate a tunable laser exhibiting 11 discrete modes over a 30 nm tuning range with mode spacing around 400 GHz and side-mode suppression ratio larger than 30 dB. The individual modes can be continuously tuned by up to 1.1 nm by carrier injection and by over 2 nm using thermal effects. These mirrors are suitable as a platform for integration of other optical functions with the laser. This is demonstrated by monolithically integrating a semiconductor optical amplifier with the laser resulting in a maximum channel power of 14.2 dBm from the discrete modes.