Design And Transmission Characteristics Of Micro-nano Optical Device With MDM SPP Optical Waveguide Coupled Multi-resonator

Over the past decade,Surface Plasmon Polaritons(SPP)excited at the metaldielectric interface have attracted many researchers' attention,because of its highly localized confinement,which can break diffraction limits and have long range propagation characteristics.And it is widely used in nonlinear optics,biosensor,integrated optical circuit chips and many other fields.As an important branch,Fano resonance generated by the coherent interference of the bright and dark modes of SPP,has become a hotspot in micro-nano optics due to its high quality factor(Q)and the steep line shape with small distance from peak to trough.Especially Metal-DielectricMetal(MDM)waveguide coupled resonator structure is more suitable for highly integrated optical circuits because of its convenient layout,small size,ease of integration and other advantages.This study is a basic theoretical work on the propagation modes of SPP in MDM structure and its interaction among different resonator structures.Then the structure design and performance optimization are analyzed according to the specific application requirements.Aiming at the problem that it is difficult to tune the multi-mode resonance peak independently in MDM refractive index nanosensor,we put forward a nanosensor based on multiple independently tunable Fano resonances by choosing suitable resonant cavity and the coupling way.The dimension of the device is only 1200×700 nm,and the maximum sensitivity is up to 1900 nm/RIU.It laid a theoretical foundation for practical application of multi-mode refractive index sensor.In addition,the device also has slow light effect,and the group refractive index is 16 when the transmission is 0.43.The design concept of the whole structure can also provide the theoretical guidance for the design of slow-light devices.In order to solve the problem that the output power ratio of the MDM demultiplexer cannot be directly adjusted,we design a demultiplexer with tunable output power ratio based on half nano-disk resonator and E7 liquid crystal arrays.Firstly,1×2(1310nm,1550nm)demultiplexers with good performance were designed.A theoretical model suitable for this structure was extended by rewriting the equations of the original coupled mode theory.The reliability of the simulation results was verified by the fitted curve with excellent performance,which is obtained by comparing the numerical simulation results with the model.Then we adjust the output power ratio by changing the applied voltage,which is based on the electronic birefringence properties of E7 liquid crystal and side-coupled resonator arrays.As the applied voltage increases from 1v to 60 V,the output power ratio can gradually change from 1:30 to 20:1,the Q-factor of the output port of 1310 nm and 1550 nm are 54.6 and 36,and the crosstalk value are-20.7dB and-29.9dB,respectively,which is a kind of demultiplexer with better performance.The demultiplexer with electronically controlled tunable output power ratio is advantage to the practical application not only to significantly improve the efficiency and conserve intermediate devices to decrease the insert loss,but also to improve the adaptability of multiplexer and the flexibility of the whole system.Therefore,this structure has strong application potential in on-chip plasmonic systems and photonic integrated devices.The analysis of the properties of side-coupled resonator array can also provide a guiding reference for the design of MDM structure filter.And the introduction of E7 liquid crystal can also provide new ideas for the future design of optical,electrical and temperature control of related devices.