Optical Analog Computation Based On Surface Plasmon Polariton And Spin Hall Effect Of Light

Optical analog computing is a concept that scientific calculation is based on optical elements.Due to its ultra-fast computing and low-energy-consumption,a lot of scientists focus on this field.In recent years,great progress has been made in optical analog computing due to two aspects.Firstly,the size of optical device gets much smaller.Traditionally,the optical calculating device needs bulky system of lenses and filters.However,sub-wavelength size of optical calculators have been realized recently.Secondly,element structure is much more easily fabricated than before,which not only greatly reduces costs,but also enhances the working stability.In this thesis,we mainly talk about spatial differentiation operation which is important in the field of optical analog computing,and is mainly used in the field of science and enggineerings.To minimize the optical differentiator as much as possible,we utilize two principles to design the differentiator,which are surface plasmon polariton(SPP)and spin Hall effect of light(SHEL)respectively.The optical differentiator exhibits simple structure based on the two principles.The key to realize the spatial differentiation based on SPP is to modulate the leaky loss and intrinsic absorption loss of SPP field to realize the critical coupling condition.To understand these concepts,we first construct' spatial coupled-mode theory,which can describe the spatial distribution of optical fields well.We then derive the condition that spatial differentiation can be satisfied through transfer function and spatial-mode-coupling-interference respectively.The spatial differentiator based on SHEL is to utilize the effect that transverse shift is generated during the reflection or refraction process on simple optical surface for circular polarized beam.Such generalized effect is independent on the wavelength and material properties.Therefore,the differentiator based on SHEL has advantages of insensitivity of structure parameters and high working stability.The design principle of the differentiator will be discussed in detail in this thesis.By using two cross-orthogonal polarizers in input and output ports respectively,we show that the optical planar interface is enough to realize the spatial differentiation.With the help of the two principles,the more complicated divergence operation can be realized.In the last chapter,we design the silicon-graphene structure to realize this operation.The operation touches on dimension of vectorial optical field.This work provides a new way to process vectorial optical field and may be helpful for the optical vectorial information process in the future.