Measuring the optical properties of a trapped ZnO tetrapod

We report the onset of lasing from an electrodynamically trapped ZnO tetrapod. Each of the four legs of such an isolated tetrapod behaves as a single nanowire, where light is guided along the length of the wire and the necessary resonant feedback for lasing is provided at the two end facets. A diluted solution of ZnO tetrapods in methanol was sprayed in the form of a charged mist into a chamber containing the electrodynamic endcap trap. The quick evaporation of methanol assisted in trapping a single charged ZnO tetrapod. The trapped tetrapod is optically pumped with pulses from a Q-switched laser at a wavelength of 355 nm and emits light at 390 nm. For increasing pump fluences above 15 mJ/cm², a superlinear increase in intensity and a narrowing in the spectral width of the photoluminescence were observed, indicating lasing.