Quantum-dot based distributed feedback lasers and electro-absorption modulators for datacom applications

The unique properties of quantum dots (QDs) as gain material for semiconductor lasers result in advantageous characteristics like high temperature stability, low noise, low feedback sensitivity and low chirp. Their low internal losses make QD based devices suitable for high-speed telecommunication applications. Increase of data transmission rate by wavelength division multiplexing techniques requires temperature stable longitudinal single-mode transmitters. We present 1.3 μm index-coupled QD distributed feedback (DFB) lasers with p-doped active region showing wide temperature independent operation, high side-mode suppression ratio (> 55 dB) and quantum efficiencies up to 40%. The data rate achieved by direct modulation is exceeded by using QD electro-absorption modulators (EAMs) based on the Quantum-Confined Stark Effect. Presently we achieve a 3 dB-bandwidth of 17 GHz and extinction ratios of 18 dB. Monolithic integration of both, DFB and EAM, into a single two-section device provides an inexpensive transmitter unit suitable for metropolitan area network applications.