Semiconductor nanolasers

Semiconductor nanolasers represent the current frontier of research in the confluencing area of nanotechnology (or nanophotonics) and semiconductor lasers. In this paper, we review some of the most exciting progress made recently in the area. We will focus on nanoscale lasers made of semiconductor nanowires grown in a bottom-up fashion or nanopillars that are produced through a top-down wafer etching. Special features of these nanolasers will be reviewed. In particular, recent results on metal-semiconductor plasmonic lasers will be presented which represents the smallest lasers by taking advantages of surface plasmonic effects. Due to the small size and strong confinement in these nanolasers, certain familiar concepts in semiconductor-laser physics need to be re-examined to determine their validity or implication at nanoscale. These include the concept of modal gain and confinement factor (CF). The seemly abnormal behavior of CF in dielectric and plasmonic nanolasers will be explained from a unified point of view. Throughout this tutorial, we attempt to address the question of how small a laser can be made or whether there exists an ultimate size limit for a laser. Laser intensity profile along a nanowire laser. The nanowire laser is confined to the left by the substrate and surrounded by air from all other sides.