Quantum dot laser dynamics after pulsed optical excitation

Summary form only given. The gain spectrum of semiconductor quantum dots (QDs) is inhomogeneously broadened due to inevitable dot size fluctuations. If the homogeneous broadening is small, only QDs of the same size interact with each other via the photon field and lasing can occur on many wavelengths simultaneously. In this respect, the system QD/barrier material resembles a guest/host-system, much like titanium ions in a sapphire crystal. Therefore, QD lasers might be interesting candidates for mode locking. We investigate the lasing dynamics of an optically pumped gain-switched edge emitting QD laser at room temperature. The laser structure is a Fabry-Perot resonator of length L = 1.6 mm with cleaved uncoated end facets. The active material consists of 7 layers of InAs QDs embedded in GaAs and surrounded by an AlGaAs waveguide The GaAs surrounding the QDs is optically pumped with 100 fs pulses from a regenerative amplifier at an excitation wavelength of 800 nm. Lateral gain guiding is enforced by focussing the beam to a stripe of 100 /spl mu/m width, along the full length of the laser resonator. The emission from the edge of the sample is measured both time-integrated with a germanium diode and time-resolved by upconversion.