ZnO lasing in complex systems with tetrapods

Refractive index dispersion deduced from lasing modes in ZnO microtetrapods

“…8 We suggest that this type of lasing is very probable in small tetrapods similarly to guided modes in small ZnO rods, 22,23 or in bigger tetrapods without well defined end facets of legs. On the other hand, in well faceted tetrapods with long enough legs the formation of Fabry-Pérot cavities is highly probable.…”

“…Several models of resonators have been proposed for ZnO tetrapod lasers including lasing due to longitudinal Fabry-Pérot modes in cavities formed by individual legs, [1][2][3][4] or twinned tetrapod legs, 7 or guided mode lasing due to multiple total internal reflections in twinned tetrapod legs. 8 The mode structure is strongly dependent on the dispersion of the refractive index. The wavelength dependence of the ZnO refractive index has been previously investigated by means of variable-angle spectroscope ellipsometry ͑VASE͒, 13-16 prism-coupled waveguide measurements, 17 or by analyzing the interference fringes of optical spectra.…”

“…[1][2][3][4][5][6][7][8] While the emission mechanism is common for various ZnO nanostructures it being determined by the fundamental properties and the quality of the material, [9][10][11][12] the resonators are specific for different structures. Several models of resonators have been proposed for ZnO tetrapod lasers including lasing due to longitudinal Fabry-Pérot modes in cavities formed by individual legs, [1][2][3][4] or twinned tetrapod legs, 7 or guided mode lasing due to multiple total internal reflections in twinned tetrapod legs.…”

Guided mode lasing in ZnO nanorod structures

“…It has been recently shown that carbothermal growth with vapor transport and condensation in a horizontal furnace with the substrate placed upstream of the argon/oxygen flow with respect to the ZnO/graphite powder source results in the formation of a core-shell wire consisting of a dense core and a crumbly shell formed from ZnO tetrapods [24]. In this structure, the core may play the role of a waveguide, while the shell is suitable for laser action due to guided modes in pairs of tetrapod legs.…”

Quasi-whispering gallery modes in ZnO microtowers

“…Since the ZnO refraction index in the UV radiation region at room temperature is about 2.4, the critical angle of total internal reflection is < 25 • . This fact makes the formation of laser modes highly probable as a result of total internal reflections, as we have mentioned in [1,2] for ZnO rods and tetrapods.…”