Passive mode-locking of p-doped quantum dot semiconductor lasers

Abstract

Quantum dot based monolithic edge-emitting semiconductor lasers at 1.25 µm are ideal sources for the generation of broad optical frequency combs for optical communication applications. In this work, InAs/InGaAs quantum dot lasers with different total laser length to absorber length ratio and with different p-doping concentrations in the GaAs barrier sections are investigated experimentally in dependence on the gain injection current and absorber reverse bias voltage. A smaller mode-locking area is found for the p-doped device in dependence on the laser biasing conditions. For the undoped active region 1.3 ps short pulse widths at a pulse repetition rate of 20 GHz with a pulse-to-pulse timing jitter of 111 fs are reported for an absorber section length of 12% to the total cavity length. For an undoped and p-doped device short pulse emission between 2.5 ps and 5.5 ps is attained and a shorter absorber section length of 8% or 5%.