Front Cover (Phys. Status Solidi A 11/2009)

Is laser cooling of semiconductor quantum dots by phononassisted anti-Stokes photoluminescence possible? The Feature Article by Rakovich and coworkers (p. 2497), featured on the front cover, attempts to answer this question by describing the basic principles of this phenomenon and discussing the progress and future challenges of the field. Recent experimental advancements made it possible that all the requirements for optical cooling using semiconductor nanocrystals are finally met. The appropriate electronic structure, strong electron-phonon interaction, high quantum efficiency of photoluminescence and the efficient thermally-stimulated anti-Stokes photoluminescence in quantum dots are all very favorable conditions for the first observation of optical cooling. The question about the feasibility of anti-Stokes cooling with quantum dots is about “when” rather than “if”.