Surface plasmon-polariton amplifiers

Propagation of surface plasmons at metal surfaces is receiving much interest nowadays because of its broad range of potential applications, like subwavelength photonics or biosensing. Although plasmonic devices achieve unique properties, surface plasmons suffer from high attenuation because of the absorption losses in the metal. This limitation can be overcome by providing the material adjacent to the metal with optical gain. Under these conditions, absorption losses are compensated and the propagation length of the plasmon is significantly increased. In this work, a review of plasmonic amplifiers is presented. To this end, the state of the art of such devices and the propagation characteristics of surface plasmons under amplification are described. Finally, a novel material based on the incorporation of colloidal quantum dots in a polymer matrix is proposed as a gain medium. This kind of nanocomposite (polymer+quantum dots) is important because it combines the novel properties of colloidal quantum dots (temperature independent emission and color tuning with the base material) with the technological feasibility of polymers. Wavelength tunability of the device (from 400 nm to more than 2 μm) is achieved by changing the material of the dots and their size. Furthermore, electrical injection is possible in the future.