2.18 μm random laser action based on Cr2+:ZnSe nanocrystalline particles

An approach for fabricating Cr2+:ZnSe nanocrystalline particles by 355 nm nanosceond laser ablation of polycrystalline micron-sized powder in liquid environment is presented. The scanning electron micrscope and X-ray diffraction results reveal that the products are ZnSe cubic sphalerite structured nanocrystalline particles with an average size of 50 nm. Based on the Cr2+:ZnSe nanoparticles, typical random laser emissions centering at 2180 nm with a threshold of 0.35 mJ/pulse are observed for the first time. Compared to the micron-sized powder, it shows a blue-shift of 170 nm. With the pump energy increasing (above the threshold value), the decay time reduces to 30 ns from 1.2 μs. Our experimental results demonstrate that the Cr2+:ZnSe nanoparticles random lasing emission appears in a wide pump wavelength range from 1500 to 1900 nm. The comparsions of the fluorescence, excitation spectra and threshold features between micron-sized particles and nanoparticles are also presented.