Coherent control of biomolecules and imaging using nanodoublers

Abstract

In the quest for the next generation of imaging bio-markers, successful probes have to prove to be non toxic, bright, stable against long term excitation, and able to generate a sharp contrast against background fluorescence. In all these respects, Harmonic Nanoparticles (HNPs, "nanodoublers") are receiving an increasing attention as they also open a series of alternative detection possibilities simply not accessible with the present generation of fluorescent dyes and quantum dots. In the first part of the chapter, we report on this novel labelling method with unprecedented wavelength flexibility, enabled by the non-resonant nature of the second harmonic process. The possibility of employing infrared excitation and the consequent deeper tissue penetration is especially promising for their in vivo applications [1]. The phase-coherent optical response of HNPs can also be exploited to fully characterize the excitation laser pulse in the focal spot of a high-NA objective with nanometric resolution. This proof-of-principle "nano-FROG" experiment [2] sets the ground for further phase-sensitive self-referenced applications, after the recent demonstration of harmonic holography and heterodyne detection with external references. © 2013 Springer Science+Business Media Dordrecht.