Diffraction Control Based On Subwavelength Optical Materials And Its Application In Optical Interaction

Owing to the development of(micro-)nano-fabrication technology,optical devices are becoming thinner,more compact and cheaper.Compared with the traditional optical components,optical devices based on subwavelength materials have the advantages of flexible design,high efficiency and easy integration.Subwavelength optical materials are gradually used in optical communication,flat panel display,optical stealth and other fields.By reasonable design,subwavelength structural optical devices are able to modulate light amplitude and phase,which brings about a variety of novel devices with special functions.In this dissertation,a type of multichannel high-extinction-ratio polarization beam splitter is designed to control the diffraction characteristics of incident light,upon subwavelength gratings with multi-slits in a pitch.In addition,by utilizing the coupling character,the application of subwavelength gratings in optical interaction is proposed and demonstrated.The system has the advantages of remote controlling,quickly dynamic response and low cost,which provides a new approach for human-machine interaction.The main content of this dissertation can be summarized as follows:1)A multi-channel polarization beam splitter based on multi-slit sub-wavelength grating structure is proposed,which resolves the contradiction between the diffraction efficiency and extinction ratio of traditional single-slit grating,the higher extinction ratio for each channel and more flexible angle beam splitting are realized.By combining grating diffraction,MIM waveguide mode,and F-P cavity resonance,the relationships of the parameters such as slit width,slit height and grating pitch for structural characteristics are revealed via rigorous coupled wave analysis(RCWA)method.2)By using the fabrication process,the high performance polarized beam splitters were fabricated,and the spectral properties of the devices were measured.Finally,a multi-channel polarization beam splitter with extinction ratio greater than 20 d B per channel is realized.3)A 3-D optical interaction scheme based on double-layer sub-wavelength grating structure is proposed,and the sensing of incident wavelength and angle is realized.By using grating diffraction and waveguide coupling theory,the physical correlation between the detected signal and the position of incident light is revealed,and the general formula of the correlation is derived.4)The large area grating film was fabricated by nanoimprint technology,and the signal acquisition and measurement system of 3-D optical interaction system was built.The real-time detection of angle and position with mean absolute errors of 2.94° and 1.65 mm is realized.