Advanced photonic devices for Telecom applications

Anticipating the needs of the Optical Telecom Network evolution, an activity on lasers for Telecom applications is carried out in the III-V Lab. This activity encompasses developments in : Quantum Dots (QD) lasers and amplifiers, mode-locked lasers, Photonic Crystals (PhC) based lasers and amplifiers, and functional semiconductor devices for all-optical signal processing.

During the past few years, self-assembled semiconductor QD lasers have attracted considerable attention, since they are expected to present lower threshold current, lower chirp, higher gain, and higher thermal stability than quantum well devices. For a 310 µm long BRS QD laser in a high reflectivity/cleaved facet configuration, the sensitivity at BER = 10^-10 equals –13.5 dBm and – 9.6 dBm, with extinction ratio of 5.9 dB and 3.2 dB at 25 °C and 75 °C respectively.

Mode-locked QD laser diodes are attracting a great interest as they provide large lasing spectrum and fast carrier dynamics. They are perfectly suited for the generation of short pulses and for all-optical clock recovery. This figure shows the eye diagram of the incoming OTDM signal (top) and the recovered clock (bottom). A high quality clock signal with high extinction ratio (> 13 dB) is observed.

Due to their small size and mass production potential, Semiconductor Optical Amplifier (SOA) can foster the market for low cost optical amplification in metropolitan optical networks. To meet the system requirements, SOA must exhibit an optical fibre to fibre gain greater than 10 dB and a noise figure (NF) lower than 7 dB. New SOA designs have been developed to meet these challenges (figure: SEM view of a 2 µm pnBH SOA stripe after MOCVD regrowth).