Laser-tuned whispering gallery modes in a silica-based microsphere resonator integrated with ethyl-orange-doped polyvinyl alcohol coating

Abstract A laser-tuned whispering gallery modes (WGMs) microsphere resonator integrated with ethyl-orange-(EO-) doped polyvinyl alcohol (PVA) coating has been proposed and experimentally demonstrated. Owing to the photo-induced isomerization feature of the azo-doped coating, the WGM resonance wavelength could be tuned by adjusting the 532 nm excitation laser power density based on a lateral pumping scheme. The WGM tuning principle of the proposed microresonator has been investigated, which is in accordance with our experimental observation results. Experimental results indicate that the proposed functionalized microsphere has a fully linear WGM resonance wavelength tunability up to 0.158 nm/(mW mm −2 ). Further experimental study shows nonlinear WGM resonance wavelength shift respectively dependent on EO weight percentage and pump laser power densities, which is in agreement with our theoretical analysis. Moreover, our proposed microresonator also exhibits good spectral reversibility as well as dynamic temporal response, which ensures its potential applications in optical modulation and future all-optical networking systems.