Arbitrary function resonance tuner of the optical microcavity with sub-MHz resolution

Tuning the resonance frequency of an optical whispering gallery mode microcavity is extremely important in its various applications. Here we report the design and implementation of a function resonance tuner of an optical microcavity with a resolution of about 650 kHz (7 pm at 1450 nm band). A piezoelectric nano-positioner is used to mechanically compress the microsphere in its axial direction. Furthermore, the resonance can be periodically tuned as an arbitrary function, such as the sine and sigmoid functions, with over 99% fitting accuracy. This Letter greatly expands the application of ultrahigh quality factor micro-resonators in a multi-mode coupling system or time-floquet system. (C) 2019 Optical Society of America