Research On Near-Infrared Control Of Micro-nano Composite Structure Based On Surface Plasmons

As the rapid development of modern information science,the pure electronic devices have been unable to meet the high data streams required for transmission and storage due to some inherent limitations of their own.Photons have the characteristics of no rest mass,fast signal transmission speed,and easy realization of multi-channel communication.It is an ideal candidate for a new generation of information carrier.However,traditional optical devices are difficult to achieve miniaturization and integration in the nanoscale dimensions due to the difficulty of diffraction limit,which seriously hinders the development of related research.The appearance of surface plasmons(SPs)provides a practical way to solve the above problem.SPs is an electromagnetic mode of non-localized free electron collective oscillation formed by the coupling of incident light field existing at the interface of metal and dielectric material.It can be divided into surface plasmon polaritons(SPPs)and localized surface plasmon resonance(LSPR).This surface electromagnetic response has a sub-wavelength binding scale,breaking through the diffraction limit,and has significant field enhancement characteristics.Especially with the unique dispersion performance and structural sensitivity,it can realize multi-dimensional control of the amplitude,polarization and phase of the electromagnetic wave.Researchers combined the SPs with the theory of optical extraordinary transmission(EOT)and the concept of super absorption,and achieved remarkable results in the fields of high-resolution imaging,biological environment sensing,nonlinear optics and energy harvesting.However,the above plasmonic optical elements still face many challenges,especially in the near-infrared region,the problems such as long bandwidth,noise interference,and low responsiveness generally exist.In this thesis,we mainly focus on the topics of near-infrared high-resolution filters and super absorbers.The hybrid coupling effect between different SPs modes is established through the metal/dielectric micro-nano composite structure to obtain high-quality resonance characteristics,aiming to realize the plasmonic light-field modulator with the characteristics of precise regulation,strong out-of-band suppression and narrow mode width.In addition,this paper combines coupled cavity resonance theory,SPP dispersion relationship and finite-difference time-domain(FDTD)principle to form a relatively complete mathematical analytical model,andconducts in-depth research on the physical mechanism of the spectral response characteristics.Finally we summed up the corresponding optimal control measures.The main research contents of this study are as follows:(1)Aiming at the difficulty of combining extremely narrow transmission,high responsiveness and out-of-band suppression in the near-infrared region of plasmonic filters,we used a new type of cavity-driven composite grating array based on the SPP mode coupling effect provided by different metal/dielectric/metal(MIM)and metal/dielectric(MI)grating modules,to realize low noise,narrow band,and tunable EOT phenomenon in the near-infrared window.In this structure,the MIM grating dielectric cavity plays an important role in the transverse Fabry-Perot(FP)resonator.It provides driving energy for the system,and effectively regulates the energy distribution and resonance wavelength of the internal coupling field.At the same time,it is also the structural basis for the formation of Fano resonance,thereby forming a narrow-band transmission response.We further studied the physical mechanism of SPP coupling process and narrow-band transmission through the FDTD algorithm and SPP dispersion theory.Then we analyzed the effect of LSPR on the transmission intensity,and used its local enhancement feature to improve the spectral transmittance.Finally,we have significantly enhanced out-of-band suppression by optimizing the dielectric layer thickness and the ratio of different grating length.The composite grating system can compress the transmission linewidth below 10 nm,and the corresponding quality factor is as high as 174.3.(2)In response to the problems of excessively long linewidth and low high-frequency peak transmittance of the single-layer metal nano-hole array,we have achieved significant dual-passband linewidth reduction effect in the near-infrared regime by integrating MIM resonators,in which the spectral linewidths of high-frequency and low-frequency transmission passband are reduced by 2/3 and 1/2,respectively,and the transmission intensity of the high-frequency peak is increased in this process.The cavity-coupled MIM nano-hole array also has the characteristics of simple design,flexible modulation,and polarization insensitivity.In the process of studying the SPP coupling field and energy flow distribution in different resonance states of the filter,we analyzed the modulation function of the FP coupling cavity in the reduction of the linewidths and the change of the dual-peak transmittance.In addition,by reasonably adjusting the thickness of the dielectric layer and the duty cycle of the hole array,the side-peak noise in the high-frequency transmission mode iseffectively suppressed.Finally,we revealed the modulation effect of gold film thickness on mode width and transmittance.(3)In order to realize the dual-narrowband super absorption characteristics in the low-noise background in the near-infrared regime,we designed a new MIM hybrid-cavity compound grating array to achieve this purpose.The two corresponding peak absorption of this structure exceed 94%,and both the quality factors exceed 80.Through the study of the coupling field distribution and dispersion characteristics of different resonance states,we proposed the cavity-coupled gap plasmon polariton(CGpp)theory,which explains the physical mechanism of each absorption band in detail and quantifies specific influence of the equivalent end-face phase on wavelength shift.In addition,we systematically analyzed the modulation effects of different structural dimensions on the near-infrared absorption response,and established the correlation between the LSPR phenomenon and the absorption intensity using the end-surface equivalent electric field model.This structure has excellent ability to regulate and control the local light field,and can move the response wavelength to an ideal position.In the environment with different refractive indexes,its unit refractive index sensitivity can reach 1012.5 nm/RIU,and the figure of merit(FOM)function is as high as 235.5,which is a relatively ideal value.