Transmission And Detection Of Plasmons In Micro-nano Metal-Semiconductor Structure

Modern high-speed communication systems and computer chips have higher requirements for information acquisition,processing and transmission rates.At present,the development of large-scale integrated circuits has entered a bottleneck stage.The problems of interconnect delay,clock skew,on-chip crosstalk and power consumption are becoming more and more serious.Although photoelectric integrated circuits have the advantages of small size,high reliability,ultra-high speed and low noise,traditional photoelectric devices are limited by diffraction limit in practical applications,and the effective size of components is in the micron level,so it is difficult to achieve high integration.At the same time,there is a serious size mismatch between optical and electronic devices,which makes it difficult to effectively integrate with the nano-electronic devices that have been widely used at present.Surface plasmon polaritons(SPPs)which are oscillations of the electron gas at the interface between metal and dielectric can be limited in the wavelength range,and have high speed transmission of information,so they can be used as information carriers instead of photons and electrons.The plasmonic interconnected circuits are built combining the compactness of nano-electronics with a high-bandwidth characteristic of optics,so it is currently one of the important development directions in the field of optoelectronic integrated circuits.In the interconnection circuits with plasmon as the information carrier,the readout process(energy conversion between plasmon and electron)of plasmon signal is a decisive factor that restricts the operation speed and signal transmission rate of the interconnection circuit with plasmon,so the plasmon detector has received extensive attention from researchers.However,the currently reported surface plasmon detector only achieves the function of principle verification,and its signal conversion efficiency and conversion efficiency cannot meet the requirements of future high-speed and low-power communication chips.Therefore,new micro/nano electronic devices are urgently needed to realize the efficient and high-speed conversion from plasmon signal to electrical signal.In this thesis,considering the problems of low detection efficiency,complex preparation process and difficulty in integration in existing SPP detection structures,the feasibility and working mechanism of SPP detection in periodic gratings which is compatible with CMOS technology and easy to integrate were studied.On this basis,the structural parameters of the SPP detector based on periodic gratings were optimized to improve the detection performance.This work provides theoretical and experimental basis for the realization of high-efficiency and high-speed SPP detector and the construction of PICs.The main research achievements of this thesis are as follows:(1)A SPP detector based on periodic grating structure was proposed.The relationship between the coupling efficiency and the polarization angle of the incident light was analyzed by numerical simulation along with that between the absorption efficiency and the waveguide length.The operation principle of the SPP detector was also described.Further,the corresponding SPP detector was prepared by electron beam lithography(EBL)process.Through optoelectronic measurement system,the influence of incident light power,polarization state and incident area on the response current was investigated in detail.The experimental results are in an agreement with the simulation data,demonstrating the feasibility of detecting SPP in periodic grating structure.(2)The periodic grating structure was optimized to be interdigitated grating structure by finite difference time domain method(FDTD).Where after,the detection efficiency of SPP in interdigitated grating-silicon substrate structure was discussed.Additionally,the response time of interdigitated grating-silicon substrate structure and the detection structure based on periodic grating was comparatively studied from theoretical model and experimental measurement.It showed that the responsivity and response time of the SPP detector were increased by 2.5 times after optimization.(3)In view of the low coupling efficiency of the excitation structure,the material and structure of the excitation end are designed and optimized.The focus is on the design and realization of the directional transmission of the excitation element.The Bragg grating structure is constructed to improve the intensity of the unidirectional propagation of surface plasmons to improve the coupling efficiency of the excitation element and reduce the energy loss.The structure of binary grating is fabricated by electron beam lithography,and the effect of Bragg grating on the coupling efficiency of plasmon is verified by experimental tests,which provides a reference direction for the realization of efficient plasmon detectors in the future.