Non-conventional white light emission of Al$_{2}$O$_{3}$ induced by laser diode excitation

We discovered broadband yellowish white light emission from commercially obtained nominally un-doped $\gamma $-Al$_{2}$O$_{3}$ nano-powders with a crystalline size of less than 50 nm. This emission was obtained under 975 nm laser diode excitation. We measured the spectrum, decay time, and rise time of this white light under a variety of conditions, such as various environment pressures, temperatures, pumping powers and pumping wavelengths. We also studied the decay- and rise times of various wavelengths within the emission spectrum. The white light spectrum was ranged from 450 to 950 nm. Its intensity was not dependent on the temperature of the samples, but was strongly dependent on pressure, with higher values at low pressure. It was also dependent on pumping laser power.