Nanofocusing: reaching out

Nanofocusing, the term coined by Mark Stockman, has been observed in many different tapered waveguide configurations, demonstrating the possibility for optical modes to be efficiently delivered to and concentrated into nanoscale regions far beyond the diffraction limit in dielectric media. Strong and broadband local field enhancement and slowdown effects associated with the nanofocusing have been exploited for enhancing linear and nonlinear optical phenomena and reaching out to a broad spectrum of diverse applications, from electron generation to water vaporization. Starting with the historical background, we carefully elaborate on the basic concepts and mechanisms involved. We then provide examples of the latest developments in this exciting quest for bringing the fundamental physical phenomenon of nanofocusing into the realm of practical applications in modern nanotechnology.