Enhanced optical confinement and lasing characteristics of individual urchin-like ZnO microstructures prepared by oxidation of metallic Zn

Abstract

We prepared urchin-like micron-sized ZnO cavities with high optical quality by oxidizing metallic Zn and proposed the mechanism that resulted in the growth of the urchin-like microstructures. The photoluminescence spectra of the ZnO microstructures had a predominant excitonic emission at room temperature. The lasing properties of the urchin-like ZnO microstructures were investigated systematically through excitation power- and size-dependent photoluminescence measurements. The results showed that a low lasing threshold with high quality factors could be achieved because of the high reflectivity of the optical reflectors formed by the tapered nanowires. The unique optical characteristics may facilitate the development of high-efficiency random lasers.

Polycrystalline ZnO nanorods for lasing applications

“…However, the diameter of our nanorods is too small (less than 200 nm) for this to occur especially in its current resonator structure. [33][34][35] The nature of random lasing in polycrystalline ZnO nanorods' mats could be further investigated in future studies, for example, by looking at the spatial extent of lasing modes 10,36 and studying its dependence on sample parameters such as the thickness of the mat, the alignment of the nanorods, and the role of the polycrystalline structure. Our work is a first step toward implementation of chemical bath synthesis as a low-cost scalable technique for producing random laser materials, which could spark new applications such as optical sensors.…”

Lasing from ZnO nanorods on ITO-coated substrates

“…Annealing ZnO has been shown to reduce random lasing threshold and to increase the chance of lasing [7]. However, upon only sample's annealing at a temperature as low as 600 ºC, lasing was observed with a low threshold compared to structures prepared by other simple growth techniques like sol-gel methods that require annealing above 700 ºC to reach the lasing threshold [8]. As annealing reduces point-defects due to O-vacancy, Zn-vacancy, O-interstitial and Zninterstitial, near-band-edge luminescence would increase, which in turn may reduce the threshold condition.…”

Review of Open Cavity Random Lasers as Laser-Based Sensors

“…Current random lasers have been engineered toward reducing the number of lasing modes. Methods include introducing point defects, controlling absorption, and altering the Mie resonances. − …”