Research On Goos-Hanchen Shift Enhancement Characteristics And Sensor Design Of Waveguide-grating Composite Structur

The Goos-H?nchen shift(GH shift)is a transverse shift of the incident beam in the plane of incidence when it undergoes total reflection on two media,which is unlike the behavior in geometric optics.It was first observed experimentally in 1947.Due to the ultra-sensitive dependence of GH shift on wavelength and incident angle,the GH shift shows promising applications in sensors,optical information storage,optical switches and polarization beam splitters,etc.Therefore,how to realize the enhancement of GH shift has been a hot research topic in this direction.In this thesis,a composite waveguide grating structure is proposed based on a three-layer flat waveguide structure(also called thin-film waveguide structure).By adjusting the excitation of the guide mode in a compound grating waveguide structure,we achieved the transition between the bound states in the continuum(BICs)and the quasi-bound states in the continuum(QBICs).Then based on the selective excitation of the forward and backward propagating resonant guided modes,we achieved dual BICs for both TE and TM modes.By using the high Q resonance of the QBICs,the GH shift can be enhanced to more than 10~3 orders of the incident light wavelength.Moreover,we investigated the infulences of material and structural parameters on GH shift and designed an optical refractive index sensor with a sensitivity up to about 1140μm/RIU based on the GH shift in the composite structure.In the composite structure,the double quasi-BIC-assisted positive and negative GH displacements have 100%reflectivity which are more convenient in detection and application.This work will provide a useful reference for designing high-performance sensors,wavelength division multiplexers and optical storage devices based on the GH shift.