Design Of High-q Silicon Microdisk Sensor Based On End-fire Injection Mechanism

Optical active and passive devices made of silicon semiconductor material technology can effectively realize high integration and bring hope to break the bottleneck of optical devices.In addition to optical communication systems and optical information processing,silicon-based optical microcavities have received extensive attention in such fields as environmental monitoring,early prevention of major diseases and biochemical safety,due to their small mode size and high quality factor.However,commonly used micro / nano optical coupling mechanisms have disadvantages of harsh coupling conditions,high process accuracy,poor structural stability,high preparation cost or low coupling efficiency,which limit the commercialization of optical whispering gallery resonators in biomedical and biosensing applications.the advantages of the optical whispering gallery resonant cavity in biomedical and biochemical.In view of the above problems,we prove the feasibility of the direct coupling mechanism of end-fire injection from the aspects of simulation modeling calculation and experiment.Based on this mechanism,a series of temperature and refractive index sensing experiments were carried out.The main work is as follows:Based on the optical whispering gallery microcavity theory,a number of micro-disk sensor parameters including resonant wavelength,quality factor,mode volume and loss mechanism are given.The basic working principle and per formance of on-chip micro disk sensor are also discussed.Aiming at the two kinds of two-dimensional uniform grating couplers with the top silicon thickness of 220 nm and 340 nm,the finite difference beam propagation method is used to simulate the optimization and experimental verification of the parameters.Aiming at the working efficiency of the incident coupling mechanism,the finite difference method(FDTD)is used in this paper to simulate the coupling efficiency,which basically meets the need of a more efficient coupling.The fabrication process of micro / nano optical structure based on SOI material and the preparation scheme of PDMS microfluidic channel for guiding and orientation sensing were explored,and the microchannels and the effective encapsulation of the wafer were realized.Based on the above-mentioned end-fire injection coupling mechanism,an on-chip optical structure including circular microdisks was prepared.A series of temperature and solution refractive index sensing experiments were performed using the mode of high quality factor in the structure reflection spectrum.Based on the experimental results collected,the sensitivity and detection limits of the sensing system were analyzed,and the verification experiments were carried out.The direct coupling mechanism based on the end-fire injection can stimulate many modes with high quality factor in the micro-disk resonator on the basis of ensuring the high coupling efficiency.At the same time,it has the advantages of simpler and more mature preparation process,less restriction of coupling conditions and more stable structures.Therefore it is expected to exert great potential in the field of biochemical sensing and environmental monitoring.