Silicon-based Optical Microcavities And Their Applications

Thanks to the rapid development of silicon photonics and micronano manufacturing technology,silicon based optical microcavities(SOM)are playing an increasingly important role in integrated photonic circuits realm.Extensive applications can be found in lasers,modulators,detectors and sensors owing to their excellent features such as compact size,low loss and strongly localized optical field.It is a feasible idea to utilize optical microcavities to build a lab-on-a-chip platform for versatile applications.We explore the applications in Fiber Bragg Grating(FBG)sensing system,ultrasound sensing and nanoscale particle trapping based on microring resonantor(MRR)and 1D photonic crystal(PhC)cavity.Firstly,we introduce the numerical modeling method and fabrication process of SOM.Frequency domain and time domain based analysis methods are presented and the pros and cons are analyzed.The critical fabrication steps such as lithophotography and etching are elaborated.Secondly,a FBG sensing system based on athermal silicon MRR and photodiode is proposed.The silicon based MRR covered by PMMA polymer is designed,fabricated and tested.Such a FBG sensing system outperforms spectrometer based sensing systems in portability,cheapness and various application scenarios.Thirdly,we design two ultrasound sensors,which are based on a slotted SOI MRR and a 1D PhC cavity,respectively.The radius of the MRR is only 12?m and the feature size of the 1D PhC cavity is merely 0.75 ?m×13.3 ?m,both of which are far smaller than the state-of-the-art polymer based MRR ultrasound sensors.Moreover,the operation of the proposed ultrasound sensors in the telecommunication wavelength band(C band)is superior to the polymer based MRR ultrasound sensors,which using visible light sources.The 3 dB bandwidth of the novel ultrasound sensors is as high as 540 MHz.Fourthly,the Parity-Time(PT)symmetry breaking pheonmenon is studied in the coupled 1D PhC cavities.Utilizing such a concept,unidirectional light propagation with an isolation ratio of 11.63 dB is investigated.In consideration of the compact feature size and easy coupling to photonic waveguides,such a device can be exploited in optical signal processing system in future.Based on the degenerate characteristics at the Exceptional Point(EP),the proposed PT symmetric sensor shows a sensitivity more than two-fold that of traditional 1D PhC cavity based sensors.Fifthly,we studied the performance of slotted 1D PhC cavity in nanoscale particle trapping application.The results show that a polystyrene(PS)particle with a radius of only 2 nm can be firmly trapped by the proposed system.The theoretical trapping stiffness(0.4 pN/(nm· mW))and trapping potential barrier(2000 kBT/mW)are much more larger than that of traditional free space optical manipulation system and previously reported near field optical manipulation techniques.Finally,the thesis contents are summarized and the perspectives about the development of silicon based optical microcavities are given.