  In 2003 Bergman and Stockman introduced the spaser, a quantum amplifier of
surface plasmons by stimulated emission of radiation [1]. They argued that, by
exploiting a metal/dielectric composite medium, it should be possible to
construct a nano-device, where a strong coherent field is built up in a spatial
region much smaller than the wavelength [1,2]. V-shaped metallic inclusion,
combined with a collection of semiconductor quantum dots were discussed as a
possible realization of the spaser [1]. Here we introduce a further development
of the spaser concept. We show that by combining the metamaterial and spaser
ideas one can create a narrow-diversion coherent source of electromagnetic
radiation that is fuelled by plasmonic oscillations. We argue that
two-dimensional arrays of a certain class of plasmonic resonators supporting
high-Q coherent current excitations provide an intriguing opportunity to create
spatially and temporally coherent laser source, the Lasing Spaser.
