Lasing by ensemble of spasers*

We study laser action of two or more nanoparticle-based spasers in mutual electromagnetic field. We show that radiative coupling between spasers at subwavelength distance leads to spasers’ synchronization and lowers the system laser threshold relative to that of individual spasers. For spherical composite nanoparticles with metal core and dye-doped dielectric shell, we develop analytical model describing cooperative stimulated emission by a pair of closely-separated spasers.