SCIENCE SPIN-OFFS

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Inner structure of ZnO microspheres fabricated via laser ablation in superfluid helium

Yosuke Minowa, Yuya Oguni, Masaaki Ashida
(Submitted on 1 Mar 2017)

ZnO microspheres fabricated via laser ablation in superfluid helium were found to have bubble-like voids. Even a microsphere demonstrating clear whispering gallery mode resonances in the luminescence had voids. Our analysis confirmed that the voids are located away from the surface and have negligible or little effect on the whispering gallery mode resonances since the electromagnetic energy localizes near the surface of these microspheres. The existence of the voids indicates that helium gas or any evaporated target material was present within the molten microparticles during the microsphere formation.

https://arxiv.org/abs/1703.01178

1. Introduction Dielectricmicrosphereshavetheabilitytocon?nelighttoasmallvolumewithahighquality factor through internal total re?ection forming the electromagnetic eigen modes known as whisperinggallerymodes(WGMs)[1].Thestrongcouplingbetweenlightandmattero?ersa varietyofapplicationssuchasmicrolasers[2],enhancednonlinearopticaldevices[3],andcavity quantumelectrodynamics’platform[1].Thelight-mattercouplingcanbenaturallyresultedby fabricatingmicrospheresfrommaterialshavinglargeoscillatorstrength.Excitonsindirectband gapsemiconductorshavelargeoscillatorstrengths[4]andhighluminescencequantumyields, whichmakethemsuitabletobecoupledwiththemicrocavityopticalmodes