Lasing of ZnO micro / nanocrystals by ultraviolet laser excitation and atmospheric alignment with laser-induced motions and electrical field

Lasing characteristics and an alignment method of ZnO micro / nanocrystals were investigated for an application to ultraviolet (UV) laser diode (LD). A single ZnO microsheet synthesized by carbothermal chemical vapor deposition method was examined by spectra observation with a third-harmonic Nd:YAG laser (λ = 355 nm, τ = 5 ns) as an excitation laser light. The observed emission spectra showed the lasing characteristics having mode structure and a threshold for lasing at 49 kW/cm². In addition, laser-induced motions (LIM) of ZnO micro / nanocrystals at high excitation intensity beyond the lasing threshold were observed when those were excited by the UV laser beam at a repetition rate of 20 Hz. The mechanism of the LIM was discussed, and an alignment method of ZnO micro / nanocrystals using the LIM and electrical fields was demonstrated.