Spaser is an acronym for surface plasmon amplification by stimulated emission of ra-diation. A spaser is effectively a nanoscale laser with subwavelength dimensions and a low-Q plasmonic resonator, which sustains its oscillations using stimulated emission of surface plasmons. The concept of stimulated emission to sustain plasmonic oscillations in a resonator was first described by David Bergman and Mark Stockman in 2003. Using a unified notation, we provide an up-to-date literature review of the major developments and latest advances in spaser theory and carry out a systematic exposition of some of the key results useful to understand the operation of spasers. Our presentation covers both semiclassical and quantum-mechanical formulations of spaser models as well as various designs and technologies demonstrated/suggested to illustrate key aspects of this tech-nology. Even though many advances have already been made in spaser technology, there are many hurdles that need to be overcome to bring this technology up to the level of modern laser technology. We take especially great care to highlight the main challenges facing various spaser designs and the limitations of widely used methods and materials. This review is written for both specialists in the field and a general engineering-physics-chemistry readership.
- (140.3460) Lasers
- (240.6680) Surface plasmons
- (250.5403) Plasmonics
- (260.2110) Electromagnetic optics