Electronic-induced-transparency-like in a single polydimethysiloxane-coated whispering gallery mode microbubble resonator

We fabricated a polydimethylsiloxane (PDMS)-coated silica microbubble cavity with rich whispering gallery modes (WGMs). An electromagnetically induced transparency (EIT) window is realized through experimentally coupling a tapered fiber with the PDMS-coated microbubble resonator (MBR). There is a high-Q mode in the vicinity of a low-Q mode in transmission spectra. The experimental results prove that the high-Q mode performs a small redshift while the low-Q mode performs a large blueshift when the input power increases. This attributes to the negative thermo-optical coefficient (TOC) of PDMS and the positive TOC of silica. An EIT-like window is realized when these two modes are on-resonance with same frequency.