Among different anti-Stokes emissions, where emitted photons have larger energy than the absorbed photons, photon avalanche (PA) phenomenon is unique. It originates from a very non-linear incr...

Förster Resonant Energy transfer (FRET) is a generic method to study interaction between two fluorescent maieties - the donor (D) and the acceptor (A). Energy absorbed by the donor may be tran...

Use of upconverting nanoparticles (UCNPs) as donors comes with some complications. Donor ions are characterized by their long lifetimes (hundreds of microseconds) and outnumber the acceptor dy...