Random Lasing from a Layer of ZnO Powder Painted on Glass Substrate under Excitation of Nanosecond and Picosecond Laser Pulses

Abstract

The ZnO powder which consists of monodisperse colloidal spheres with average diameter of 100-300 nm was synthesized by hydrolysis of Zinc acetate dehydrate. The random lasing around 380 nm was produced from a layer of the ZnO powder painted on a glass substrate and optically pumped at 355 nm. Our experimental results show that random laser action of a layer of ZnO spherical nanoparticles and the characteristics of these random lasers under excitation of nanosecond and picosecond laser pulses.

Structural instability and dynamic emission fluctuations in zinc oxide random lasers

“…As others before us, 4,5,7,[11][12][13] we find strong spectral fluctuations in the lasing output when nanosecond pulses are used for pumping, while picosecond pumping generates very reproducible lasing spectra. From the results presented here, it appears unlikely that the shot-to-shot spectral fluctuations in nanosecond pumping are caused by structural damage.…”

“…For the case of long excitation pulses, i.e., pulse durations of several nanoseconds, we find a very low degree of reproducibility in the emission spectra, similar to what has been observed by others. 4,5,7,[11][12][13] This stochastic behavior contrasts to the high reproducibility 4-7 observed with picosecond excitation pulses. While one might suspect the stochastic behavior also to be caused by material damage, our results indicate that this is not the case.…”

“…Also, the observation of much higher reproducibility in picosecond pumping at pulse fluences well above the damage threshold indicates that damage is not the cause for stochastic lasing behavior. Alternative causes have been discussed in several publications [4][5][6][7][11][12][13] which point to the shorter recombination lifetimes in the ZnO nanoparticles as compared to bulk ZnO: Essentially, when the recombination lifetimes are substantially shorter than pump pulse times, temporal sequences of un-coupled lasing events can occur within a single pump pulse, and the dynamic evolution of these sequential lasing events is suggested to produce the large shot-to-shot variations in nanosecond pumping.…”

“…[1][2][3] Efficient excitonic emission from ZnO nanoparticles and comparably long exciton lifetimes make the material an interesting candidate for ultraviolet optically pumped random lasing. 1,[4][5][6][7][8][9][10][11][12][13] Ease of fabrication, small mode volumes, and a variety of spectral characteristics lend themselves to three basic applications for ZnO random lasers: (A) The possibility of speckle-free lasing originating from a non-resonant amplification or the superposition of a large number of optically independent lasing events, (B) the possibility of generating unique spectral distributions from the combinations of just a few random lasing spots, and (C) the possibility of preparing coherent nanoscale lasing sources in simple thin film arrangements. These applications utilize coherent and incoherent lasing regimes, and both of these regimes are accessible in random lasers.…”