We experimentally demonstrate critical coupling of whispering gallery mode (WGM) disk resonators implemented on a Bloch surface wave platform using scanning near-field optical microscopy. The studied structure is a 60 nm thick TiO 2 TiO2 WGM disk cavity (radius of 100 μm) operating within the C-band telecommunication wavelength. An extinction ratio of 26 dB and a quality factor of 2200 are measured. Such a high extinction ratio verifies the critical coupling of the WGM resonator. This result paves the way to planar optical signal processing devices based on the proposed geometry, for which a critical coupling condition is a guarantee of optimum performance.
Tobias Kippenberg, Guanhao Huang, Mikhail Churaev, Zihan Li, Di Zhu
Arne Seitz, Andrea Bassi, Antje Keppler
Véronique Michaud, Damiano Salvatori, Baris Çaglar, Robin Samuel Trigueira, Colin Gomez