Laser cooling in semiconductors

The recent advances in the development and fabrication of semiconductor lasers have stimulated growing interest in semiconductors as candidates for optical cooling. The essential difference between semiconductors and rare-earth (RE) doped materials is in their cooling cycles. In the case of RE-doped glasses or crystals, the cooling transition occurs in localized donor ions within the host. In the case of semiconductors, the cooling cycle involves transition between extended valence and conduction bands of a direct band gap semiconductor (Fig.1). Laser photons with energy hνp create a cold distribution of electron-hole carriers. As a result of subsequent thermalization, electrons and holes become redistributed among the system’s excited states by interacting with the phonons. The charge carriers then recombine by luminescent. Indistinguishable