Tunable twin-guide laser diodes for wide wavelength tuning at 1.55 ´m

Widely tunable lasers are generally considered as key components of future optical communication networks. However, practically all widely tunable lasers that have been fabricated so far suffer from drawbacks, like elaborate calibration procedures that are required for each specific device, low output powers, and limited direct modulation capabilities. To overcome the aforementioned issues, the sampled or superstructure grating tunable twin-guide or (S)SG-TTG laser diode has been suggested recently. In this paper we will focus on the operation principle, the fabrication, and performance of the first widely tunable twin-guide laser diodes. The devices operate at ~ 1.55 µm wavelength. By means of Vernier effect tuning, the continuous tuning range of ~ 2 nm is extended to an overall tuning range of 28 nm. Within this tuning range, five supermodes are useable and can be continuously tuned without any mode hops. The side-mode suppression ratio remains between 25 and 37 dB over the whole tuning range. Without any tuning currents applied, a maximum output power of 12 mW has been achieved.