Optical Filters And Technologies For Spectral Analysis

Infrared spectral analysis technology has been successfully applied in many fields due to its unique advantages.In view of the many advantages of silicon photonic technology such as high integration,low loss,low cost and compatibility with CMOS processes,optical filters based on different types of silicon structures have been proposed one after another.Compared with traditional coated optical filters,the advantages of small size,light weight and easy tuning make their applications more flexible and reliable,and providing key device technologies for spectral analysis applications.This thesis mainly focuses on the application requirements of spectral analysis,and focuses on the study of silicon-based optical filters and its thermo-optic tuning technologies for spectral analysis.Firstly,we summarized and analyzed the research work of the multi-component infrared gas analyzer project participated during the professional practice.Based on the basic principles of non-dispersive infrared absorption method,including Lambert-Beer law and narrow-band filtering technology,we mainly analyzed the selection and design of optical modules,and set up a test platform for the calibration and performance testing of all gases to be measured.At the same time,a cross-interference compensation algorithm was proposed to compensate the mixed gases,which improved the accuracy of gas concentration measurement.Secondly,starting from the introduction of the basic structures and working principles of the micro-ring resonator,a bent-coupling single-loop filter and a vernier-type cascaded double-ring spectrometer chip were designed,fabricated and tested.Based on the thermo-optic effect and the vernier effect,the cascaded double-ring structure can achieve a wide range of spectral measurements.In the laboratory,we carried out packaging method such as gold wire bonding on the spectral chip,then scanned the wavelength range of 1561-1570nm,and obtained the calibration bias relationship(Vi,V2)that should be loaded on ring#1 and ring#2,and further conducted a spectral analysis verification experiment.In order to improve the heating efficiency,we deeply studied the structure and simulation design of the heating electrode on the silicon substrate.Based on the heat conduction equation,the thermal model of the silicon-based optical waveguide devices was established,and the thermo-optic tuning mechanisms of traditional metal and new-type graphene were analyzed.A new pattern graphene transparent nanoheater was further proposed and studied,and applied to the bent-coupling MZI structure,achieving low loss(0.06dB),high extinction ratio(>20dB),large bandwidth(140nm)silicon-based thermo-optic tuning unit device,with a 4.2?s rising time and a 7.2?s falling time,and respectively,a power consumption of 9.3mW,which provides an important foundation for further realization of high-performance thermal tuning optical filters in the future.