Laser resonators formed by two nanoparticles

摘要

We demonstrate lasing in a cavity formed by two Mie scatterers in a dye colloidal solution. Like a Fabry-Perot cavity, the feedback mechanism for lasing is based on back scattering from each particle. Strong light amplification in between the scatterer pair not only compensate its large diffraction loss, but also help to choose the particular pair out of many scatterers in the suspension to form the laser cavity. Such cavity selection is facilitated by a careful designed cone shaped excitation geometry. Detailed experimental studies on the threshold behavior, spectral characteristic of lasing emission, and output directionality are presented. A simple theoretical model provides qualitative explanation for this lasing phenomenon.