PbS quantum dot lasers: towards high quality tuneable emission across the short-wave infrared

Lead sulfide (PbS) colloidal quantum dots (CQDs) are a novel infrared gain medium, which can exhibit tunable gain across the short-wave infrared (SWIR); lasing in this material however, remained undemonstrated until recent. Here we present a random-like laser emission from PbS CQDs at 1607 nm using a silica based distributed-feedback structure. We determined this random lasing behavior to arise via heating of the CQDs from the intense pulsed laser source, causing a drift in gain. The effects of the thermal conductivity of the substrate were then explored and were seen to be a critical factor in forming stable DFB lasing. By using an alumina based grating, DFB lasing was demonstrated between 1.55 μm – 1.65 μm with linewidths as low as ~0.9 meV.