Frequency Tuning Of Whispering-gallery Microcavities And Its Application On State Transfer

The interaction between light and matter has always been the focus of scientists.The high quality factor whispering-gallery mode(WGM)microcavities have gradually become an important platform in this research field,and have been widely applied in optical rout-ing,light storage,microlaser,sensor and quantum information processing.Usually,the WGM microcavities are coupled with other systems,such NV center and atoms,so as to take its advantages to develop a richer applications.This thesis will focus on the fre-quency tuning problem,which need to be solved in the practical application of WGM microcavities,and its application on state transfer.The schedule is shown as below:1.We improved our experimental platform.Based on the actual demand,we built a WGM microcavities coupling system at room temperature.After vacuuming the device,the coupling system in the chamber can run for a long time without being polluted by the small particles in the environment.Participated in the construction of the dilution refriger-ation system,and independently built a set of coupling system of the WGM microcavities at ultra-low temperature.With the long focal microscope,we can observe the coupling situation in the cryogenic chamber in real time.2.A high precision arbitrary function tuning scheme of frequency of WGM mi-crocavities is proposed and implemented.In this scheme,the dimension of microsphere cavity is changed by mechanical compression of piezoelectric ceramics to achieve the pur-pose of controlling the resonance frequency.When selecting the appropriate parameters,this scheme can realize the accurate resonance frequency tuning of k Hz order and keep the quality factor of WGM in the same order.By controlling the voltage of piezoelectric ceramics,this scheme can tune the resonant frequency periodically in the form of any function,and the asymmetry is always low.3.A method of adjusting the resonance frequency of the auxiliary cavity is proposed to realize state transfer between WGMs that cannot be directly coupled.When adjusting the resonance frequency,the auxiliary cavity will be coupled with the other two WGMs,and can achieve the state transfer efficiency of more than 99%under linear and periodic control.This scheme also use the gradient optimization algorithm to optimize the state transfer process,which greatly improves the transfer speed.Using this scheme,the transfer process also shows strong non-reciprocity.In addition,a micro-cavity network structure based on this scheme is proposed in this paper,which has certain guiding significance for the construction of on-chip quantum network.4.Through numerical calculation and simulation,a phonon crystal mechanical os-cillator based on Si₃N₄thin film is designed.Because the resonant frequency of the me-chanical oscillator is designed in the band gap of the phonon crystal,the energy of the mechanical oscillator is difficult to be propagated out,thus improving the quality factor of the mechanical mode.The mechanical oscillator was fabricated by micro-nano machining,and a mechanical model with a quality factor of 10⁵around 21MHz was obtained.This study laid the experimental foundation for the subsequent study of cavity optomechanics.