Controlled intermixing of multiple quantum wells for broadly tunable integrated lasers

A broadly tunable MQW laser utilizing a combined impurity-free vacancy disordering and beam steering techniques is proposed and investigated experimentally. The device consists of a beam-steering section and an optical amplifier section fabricated on a GaAs/AlGaAs MQW p-i-n hetrostructure substrate. The beam steering section forms a reconfigurable single mode waveguide that can be positioned laterally by applying electrical currents to two parallel contact stripes. The active core of the gain section contains a GaAs/AlGaAs MQW that is progressively disordered such that an optical beam steered through the selected region experience a peak in the gain spectrum that is determined by the degree of disordering of the MQWs. Furthermore the MQW in the beam-steering section is disordered to the largest extent to minimize optical beam attenuation. The MQW structure was intermixed using an impurity-free vacancy induced disordering technique. The MQW sample is encapsulated with a SiO₂ film grown by plasma enhanced chemical vapor deposition (PECVD). The beam steering region is coated with a 400nm thick SiO₂ film whereas in the gain section, the SiO₂ film is selectively etched such that the thickness grades linearly ranging from 0 to 325nm. The disordering of the entire slab region is then induced by a single rapid thermal annealing step at 975°C for a 20s. Experimental results showed a controllable 10 to 60 nm wavelength blue shift of the peak of the photoluminescence spectrum corresponding to the change in SiO₂ caps thickness and a lateral beam steering range up to 20 μm over the slab region.