UV radiation of powdered ZnO pumped by nanosecond pulses

摘要

Since the intrinsic lifetime of spontaneous recombination UV radiation in zinc oxide is shorter than ～200 ps, it is of interest to obtain stimulated UV radiation of powdered ZnO with pumping pulses of nanosecond duration. This will clarify the possibility of quasi-continuous laser radiation in disordered media. At the same time, this effect can open the way for the developing of a cathodoluminescent screen with narrow spectrum and short persistence time. Investigations of UV radiation spectra of powdered zinc oxide and some disordered films were conducted. The samples were pumped by the 3-rd harmonics of the two-stage Nd:YAG-laser (λ=355 nm) with the pulse duration ～10 ns. Maximum energy density of the pumping pulses was about 160 mJ/cm~2. Spectra of spontaneous emission were recordered at 300K and 77K. In some of our powdered samples we achieved lasing at 300K. The threshold values of pumping energy density appeared to be approximately two orders of magnitude higher than those under picosecond pumping. Peculiarities of lasing in different samples are demonstrated and discussed. In the spectra of ZnO films investigated at 300K, the UV band maximum is situated at ～382 nm, while in powders of ZnO this maximum is located at ～389 nm. Besides, in the films the long-wavelength part of the UV band broadens with increase of pumping power.