Single ZnO nanowires lase

Many ZnO nanowires at a time are grown vertically on a sapphire substrate (see figure). The diameter of the wires ranges between 40 and 150 nm, with their lengths falling between 4 and 10 µm. Some of the nanowires are removed from the sapphire and distributed across a quartz substrate at a density of 10³ wires/mm² so that they can be analyzed individually. The nanowires are pumped with 1-ps pulses of 285-nm laser light focused to a 200-µm spot, with the ends of the nanowire crystals serving as cavity mirrors. The nanowire emission is fed to a NSOM via a chemically etched fiberoptic probe that is held in constant-gap mode. By measuring the shear-force feedback signal, the NSOM can collect topographical information at the same time it is gathering optical information.