Research On Digitial Silicon Optical Waveguide Devices Based On Subwavelength Structures

This article first reviews the development of silicon-based photonics,and introduces the development of passive devices and active devices.However,the improvement of waveguide integration is suppressed due to the influence of crosstalk,which mainly includes two aspects: crosstalk between waveguides and crosstalk in curved waveguides.The former increases sharply as the spacing between waveguides decreases.The latter will inevitably cause leakage,and the coexistence of multiple modes also causes inter-mode crosstalk,making the transmission efficiency extremely low.Studies have shown that the introduction of sub-wavelength structures can contribute to the further development of silicon-based photonics.Only a few sub-wavelength structure layers are needed to achieve excellent control of the waveguide birefringence.So far,sub-wavelength structures have been widely used in beam splitting devices and polarization management devices.The introduction of sub-wavelength structure can increase the freedom of device optimization.So,in this paper,the application of numerical optimization algorithm(FDTD)and simulation optimization algorithm(genetic algorithm,particle swarm optimization,etc.)are used for further research on crosstalk suppression and multi-mode complex respectively.Silicon waveguide are the basic elements in silicon photonics,and the crosstalk between waveguides has always been a big problem and paid much attention by researchers.So far,various methods have been used to suppress crosstalk,including plasma structures,photonic crystal waveguides,and slot waveguides et al.And coupling length is used as evaluation criteria.Our work is mainly to introduce a non-uniform sub-wavelength strip array between integrated optical waveguides to achieve the purpose of suppressing crosstalk,and the coupling length improved a lot.Different numbers of strips and relative positions can play different roles in suppressing crosstalk.We obtained the optimal narrow-band position and width by using computationally-optimized method combing the particle swarm optimization and MODE solutions.Compared with a pair of waveguides with introducing uniform strip arrays,the coupling length is improved by three orders of magnitude,and it is five orders of magnitude greater than the case without strip arrays.Our work also shows that crosstalk is suppressed well for waveguides with even smaller spacing,Of course,we also give error analysis to ensure the accuracy of the results.Multimode multiplexing is another important role in connecting integrated devices,especially in curved waveguide applications.It is quite challenging,since the signal transmission in multimode photonic devices is vulnerable to sharp bending due to radiation leakage and inter-mode coupling,which makes the transmission efficiency extremely low.Therefore,we carry out further work by using computational optimization based on the previous work.We combined genetic algorithms and FDTD solutions to analyze the effect of different numbers of nanohole etch on mode transmission.The former is used to optimize the position and size of the nanoholes,and the latter is used to model the structure and analyze the mode field distribution.The results show that the introduced nanoholes have a good suppression effect on the inter-mode crosstalk and reducing the bending loss.