Comparative analysis of spasers, vertical-cavity surface-emitting lasers and surface-plasmon-emitting diodes

Electrically pumped subwavelength plasmonic lasers (spasers) have attracted significant interest in recent years, but their properties are still not well understood, especially in comparison to the ubiquitous all-dielectric semiconductor microlasers (vertical-cavity surface-emitting lasers, VCSELs). Our theoretical analysis reveals that, from the fundamental physics point of view, a spaser does not differ from a semiconductor laser, as most of the energy is contained in the oscillations of electrons (free versus bound) and not in the electromagnetic field. At the same time, due to large losses in the metal, the technical characteristics of a spaser differ significantly from the VCSEL in that the spaser has at least three orders of magnitude higher threshold current density, four to five orders of magnitude wider linewidth, and a speed that is only a few times higher than in a VCSEL or an incoherent surface-plasmon- emitting diode. These results should assist researchers in making an informed choice of emitters for various particular optoelectronic applications.