%AFan, H.%AZhang, X.%AZhao, J.%ALi, S.%AHua, S.%AZhao, M.%AHu, Y.%AWan, W.%AZhai, Y.%AWen, J.%AJiang, X.%AXiao, M.%BJournal Name: Optics express; Journal Volume: 28; Journal Issue: 6 %D2020%I %JJournal Name: Optics express; Journal Volume: 28; Journal Issue: 6 %K %MOSTI ID: 10157695 %PMedium: X %TControllable coupling between an ultra-high-Q microtoroid cavity and a graphene monolayer for optical filtering and switching applications %XWhispering-gallery-mode optical microresonators have found impactful applications in various areas due to their remarkable properties such as ultra-high quality factor (Q-factor), small mode volume, and strong evanescent field. Among these applications, controllable tuning of the optical Q-factor is vital for on-chip optical modulation and various opto-electronic devices. Here, we report an experimental demonstration with a hybrid structure formed by an ultra-high-Q microtoroid cavity and a graphene monolayer. Thanks to the strong interaction of the evanescent wave with the graphene, the structure allows the Q-factor to be controllably varied in the range of 3.9 × 105 ∼ 6.2 × 107 by engineering optical absorption via changing the gap distance in between. At the same time, a resonant wavelength shift of 32 pm was also observed. Besides, the scheme enables us to approach the critical coupling with a coupling depth of 99.6%. As potential applications in integrated opto-electronic devices, we further use the system to realize a tunable optical filter with tunable bandwidth from 116.5 MHz to 2.2 GHz as well as an optical switch with a maximal extinction ratio of 31 dB and response time of 21 ms. %0Journal Article