Surface plasmon-polariton amplifiers and lasers

Amplifiers and lasers based on surface plasmon-polaritons (SPPs) have been studied for around three decades. Research in this area has experienced particularly significant growth over the past decade, resulting in the achievement of several important milestones. Convincing demonstrations of SPP amplification and lasing have been reported for various systems involving single-interface, long-range, short-range and resonant SPPs. Diverse metallic structures such as planes, films, stripes, wires and particles (some on the nanoscale) have been integrated with gain materials. Although the prospects for SPP amplifiers and lasers are bright, the field is embryonic, and much remains to be explored and improved. This Review discusses this rapidly progressing area and summarizes the most important progress achieved so far. Research directions that warrant further investigation are also suggested.