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.

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In the last decade, microlasers with biological origin have shown their great potential in biosensing and bioimaging. Several micro-structures have been developed for high quality (Q) factor biolasers including Fabry–Pérot, distributed feedback and whispering gallery mode cavities. However, the fabrication of these lasers is generally complicated and their operation is strongly affected by cavity defects. In this work, we demonstrate random protein-based microlasers fabricated by a simple one-step self-assembled method. The lasing can be achieved from microcracks with random structures. The lasing threshold is around 14 mJ cm−2 and the quality factor of lasing modes can be up to 3 × 10 3 which are comparable with other conventional biolasers. Our work opens a new possibility for the fabrication of high Q factor microlasers from biocompatible materials, with great potential for biosensing and biomedical applications.