Silicon Nanowire Waveguide Based Microcavities For Optical Multiparameter Sensor

Nowadays,the global society of human beings are in the process of informationization and intellectualization while a new era of "big data" is about to dawn.As one of the three core technologies of modern information industry,the sensing technology,which is also considered as the sense organ of information society,has developed at a rapid pace over the past decade.Different kinds of optical sensors aimed for temperature,refractive index,humidity,molecular concentration,strain,as well as some other physical,chemical and biological parameters have been widely applied in many fields,such as environmental detection,medical diagnosis,security and aerospace.Due to its ultra small foot-print,low-level on chip transmission loss,compatibility with traditional CMOS process and potentiality to achieve mass production at low cost,silicon based integrated photonic device has realized a wide range of applications in the fields of optical interconnection,optical communication and optical sensing,which makes it the most popular research area in integrated optics.The optical sensors generally have a problem of cross influence among different external environment parameters.In this dissertation,we successively proposed and demonstrated integrated multiparameter sensors based on silicon dual polarization microring resonator(MRR)and silicon one-dimenstional photonic crystal(PhC)nanobeam cavity.By applying the devices to the measurement of temperature,refractive index(RI)and humidity,simultaneous sensing of different external environment parameters is realized.Firstly,we introduced the fundamental theory of planar optical waveguide and frequently-used numerical simulation methods,presented the basic characteristics of silicon nanowire waveguide,MRR and PhC nanobeam cavity.Besides,we summarized the major fabrication processes of silicon based integrated photonic device,including spin coating of photoresist,electron beam lithography(EBL)and inductively coupled plasma reactive ion etching(ICP-RIE).Secondly,we proposed a solution to simultaneous sensing of refractive index and temperature by taking advantage of the TE-polarization and TM-polarization of silicon nanowire waveguide.We optimized the width of the silicon nanowire waveguide and the geometry parameters of the coupler to achieve simultaneously efficient excitation for the fundamental modes of both TE and TM.Transmission characterization were carried out to verify the performance of fabricated device with the aqueous solution of NaCl.The measurements show fitted sensitivities of 319±4nm/RIU and 104±3 nm/RIU for RI change while 34.1 ±0.7pm/? and 78.7±0.5 pm/? for temperature change,which demonstrates the feasibility of achieving simultaneous measurement of RI and temperature with the proposed silicon dual polarization MRR.Thirdly,we proposed a solution to simultaneous sensing of refractive index and temperature by utilizing the air mode and dielectric mode of silicon one-dimenstional PhC nanobeam cavity.Cascaded side-coupled PhC nanobeam cavities are designed to realize simultaneous excitation and resonance for both PhC nanobeam cavities.Transmission spectrum were measured to characterize the performance of fabricated device with the aqueous solution of glucose.The results show fitted sensitivities of 254.6±9.2nm/RIU and 105.5±3.1 nm/RIU for RI change while 30.1 ±0.4pm/? and 56.4 ±0.5pm/? for temperature change,which demonstrates the feasibility of achieving simultaneous measurement of RI and temperature with the proposed silicon cascaded side-coupled PhC nanobeam cavities.Finally,the geometry dimensions of the silicon dual polarization MRR were slightly adjusted to apply to temperature and humidity sensing.The experimental process of spin coating polyvinyl alcohol(PVA)film on the surface of SOI was explored and preliminary tests were performed to verify the function of temperature and humidity sensing with the fabricated silicon dual polarization MRR.