White-light nanosource with directional emission

Phys Rev Lett. 2002 Jul 15;89(3):035002. doi: 10.1103/PhysRevLett.89.035002. Epub 2002 Jun 26.

Abstract

We report the first observation of white-light emission from femtosecond laser-induced plasma in a water droplet. Such emission is not observed with water in a cell. The microdroplet acts as a lens, focusing the incident light to nanosized regions within itself and directing the emission from these regions primarily back toward the laser source. This focusing increases the intensity so that multiphoton ionization generates plasma and causes it to reach the critical density during the initial part of the pulse, enabling the rest of the pulse to heat the plasma enough to emit in the visible.