CdS(x)Se(1-x)/ZnS semiconductor nanocrystal laser with sub 10kW/cm(2) threshold and 40nJ emission output at 600 nm.

A colloidal quantum dot laser emitting at 600 nm with a sub 10kW/cm(2) threshold at 5ns pulse pumping is reported. The device has a second order distributed feedback cavity for vertical emission and incorporates a bilayer planar waveguide structure based on a film of yellow-orange alloyed-core/shell CdS(x)Se(1-x)/ZnS quantum dots over-coated with polyvinyl alcohol. A study of the amplified spontaneous regime indicates that the quantum dot gain region behaves like a quasi-three level system and that the bilayer structure design increases the modal gain compared to a single layer of quantum dots. An output of 40nJ per pulse is measured for a total pump-to-signal efficiency above threshold of 3%.