Research On Issues Related To Quantum Dot And Plasma Waveguide Coupling Syste

As information technology continues to develop,the demand for on-chip signal processing is increasing,and integrated optics technology is also being increasingly applied during this period.Surface plasmons,as a special type of surface evanescent wave,have attracted great attention.They are generated by the collective oscillation of free electrons on the metal surface under the action of external incident light and have strong light field confinement capabilities.They can well confine the light field to the metal surface while significantly enhancing the interaction between light and matter.These characteristics make it possible to effectively reduce the size of optical devices to meet integration requirements.Quantum dots,as a new type of luminescent material with small volume and good luminescence performance,are considered a good choice for future integrated optics light sources.The coupling system between quantum dots and surface plasmon waveguides is considered to be a development direction for future integrated optics.However,there are still some problems in this coupling system such as low emission rate of quantum dots and uncontrollable mode transmission direction in waveguides.This paper will start from the principle and research status of surface plasmons and design different micro-nanostructures to solve problems in quantum dot-plasmon waveguide coupling systems through theoretical calculations using finite-difference time-domain methods and finally verify their actual effects through experiments.The main research work of this paper is as follows:1.A double-hole metal resonant cavity structure is proposed,which consists of two hole-shaped microcavities and a quantum dot placed in the center of the cavity.The double-hole microcavity can cause cavity resonance effects and obtain a large quality factor Q value.The silver substrate can excite surface plasmons well and obtain a smaller mode area.These two methods can effectively enhance the Purcell effect of the structure and obtain a larger Purcell factor to solve the problem of low emission rate of quantum dots in quantum dot-plasmon waveguide coupling systems.After optimizing simulation parameters,our designed structure can achieve a Purcell factor above 6.5×10~4.2.Based on a dielectric-loaded surface plasmon waveguides,a spin beam splitter device has designed.By designing the spin coupler structure at the waveguide junction to guide the occurrence of spin-orbit coupling effects and further control the transmission direction of light in the waveguide.This structure can control the circular polarization state of incident excitation light to make energy propagate in different directions within the waveguide.The finite-difference time-domain method is used to simulate and calculate the designed structure and explore the impact of various structural parameters on design results.Simulation results show that our designed structure can achieve a beam splitting ratio of 0.95 at 532nm wavelength.At the same time,we also processed and prepared the designed device using techniques such as electron beam lithography and electron evaporation coating and tested samples.The experimental results are in good agreement with simulation results,and this spin beam splitter structure can achieve design goals well.3.A dielectric-loaded plasmonic nanocircuit with spin sorting function has been proposed and successfully verified.The device consists of a spin coupler and two branch waveguides.The spin coupler can transmit incident photons unidirectionally to an independent waveguide.In this paper,finite-difference time-domain method is used to simulate and calculate the designed device,and samples are processed and tested using methods such as electron beam lithography.Both simulation and experimental results show that at a working wavelength of532nm,using left-handed circularly polarized or right-handed circularly polarized light for incidence,the insertion loss and beam splitting efficiency of the structure can reach 0.13d B and14.8 d B respectively.At the same time,we also explored the scalability of the designed device,such as adding new nanodisks around the nanoring to achieve multi-channel guidance etc.,which proves that our designed device has good scalability.