Research On The Key Devices For Silicon Integrated Optical Gyroscope

Gyroscope is a kind of angular velocity sensor,and it is a key component in the inertial navigation system of large vehicles,such as satellites,missiles,and air planes.Optical gyroscopes employ the principle of Sagnac effect to measure the rotation.At present,largevolume high-end optical gyroscopes have good performance,and have a large market share due to the advantages of high precision,no moving parts,and high impact resistance.In the era of informatization and intelligence,the demands for the applications of gyroscopes in automobiles,small aircraft,and mobile phones continue to increase.The researches on optical gyroscopes gradually develop towards miniaturization and chip scale.Among various integrated optical technologies,the silicon photonics technology is immensely competitive and promising due to the advantages of high integration density,capability for mass production,and compatibility with complementary metal-oxide-semiconductor(CMOS)techniques.In recent years,the researches on silicon integrated optical devices emerge worldwide.With the improvement of the performance of silicon integrated optical devices and the micro-nano manufacturing techniques,silicon integrated optical gyroscopes have great advantages and research values in the current technical background.However,the reports on silicon optical gyroscopes are still quite few,and many key issues,such as the optimization of waveguide structure and the phase bias problem,need to be solved.The thesis studies the key devices for silicon integrated interferometric optical gyroscopes,including the sensing waveguides and the coupling devices.Based on the theoretical basis of optical gyroscope and focusing on the optimization of the sensitivity,this thesis proposes a waveguide coil structure and corresponding solutions to the phase bias problem as well as the passive noise problem for silicon interferometric optical gyroscopes.The main contents of this thesis can be summarized as below:(1)Based on the principle of optical gyroscopes for angular velocity measurement,the Sagnac effect in vacuum and in a dielectric medium is theoretically derived.The basic structure of the interferometric optical gyroscope and the implementation of the phase bias are presented.Based on the theory of optical waveguides,the modal characteristics and the coupling characteristics of silicon optical waveguides are discussed in detail by using the full vector finite difference algorithm and the finite difference time domain method.The manufacturing flow of silicon optical waveguides and the experiment platform of silicon optical chips are introduced.(2)A silicon integrated interferometric optical gyroscope is proposed.The integration and sensitivity of the gyroscope are optimized by designing a waveguide coil structure.The influences of the involved active and passive components on the sensitivity are analyzed.Through the static experimental results,it is found that the shot noise limited sensitivity of the gyroscope can reach 16.4 deg/s.Further,when the waveguide propagation loss reduces to 0.4 d B/cm and the sensing waveguide area is increased,the shot noise limited sensitivity can reach 0.014 deg/s,meeting the application requirement for consumers.(3)The optical spatial modes in silicon waveguides are studied.Based on the waveguide coil structure,a mode-assisted integrated interferometric optical gyroscope is proposed.By using the effective refractive index difference of different modes,the phase difference introduced in the propagation is skillfully used as the phase bias of the gyroscope.It solves the phase bias problem and avoids the integration of high-speed phase modulators.The phase bias introduced by two modes is verified by the static experiment.Meanwhile,for the crossing problem in this scheme,a novel waveguide crossing supporting two modes is proposed,and the device is characterized by the simulated and experimental results.(4)The silicon multiport-coupling devices are studied.Two kinds of interferometric optical gyroscopes with dual Sagnac loops based on the 4×4 couplers are proposed,including the 4×4 multimode interference(MMI)coupler and the 4×4 reconfigurable multiport coupler.Compared with the traditional gyroscopes based on a 2×2 coupler,these schemes utilize the phase relationship between the ports of the 4×4 couplers and two Sagnac waveguide loops to achieve highly sensitive phase bias.The 4×4 reconfigurable multiport coupler is dynamically adjustable,and it can reduce the passive noises in the waveguides.The operating principles of the devices are introduced in detail,and the relative sensitivity can theoretically reach 0.5.