Strong Transmission Characteristics Of The Mems Metal / Dielectric Photonic Crystal Research

MEMS infrared gas sensor has excellent selectivity,sensitivity and stability owing to using spectral characteristics of gas as measurement.Thereinto,the research on MEMS infrared light source,which is the key components of it has been concerned in recent years.With the development of nanometer plasmonic crystals technology,it was noted that using the characteristics of two-dimensional metallic subwavelength (hole diameter less than half of the wavelength of incident light) round hole arrays (TDMSHA) to select a specific wavelength of light and enhance extraordinary optical transmission(EOT),it is possible to provide an effective means of fabricating MEMS infrared radiation light source having a very good selection and enhancement in a specific range of infrared light.In this paper,MEMS infrared gas sensor as the goal of application,we design and fabricate the metal/dielectric photonic crystal(MDPhC) combined structure with TDMSHA and silicon-air photonic crystal using MEMS technology.The purpose is to fabricate the plasmonic MEMS infrared light source,which can emit high performance,tunable narrow-band light by using these tailor-made properties of MDPhC enhanced the blackbody radiation spectrum transmission and filtering.The three kinds of structures were investigated mainly by us in this paper,namely MDPhC,metal/metal/dielectric photonic crystal(M/MDPhC) and metal/dielectric/metal photonic crystal(M/D/MDPhC),we systematically explored the effect of new phenomena and new features of the EOT for three different structures to enhance the characteristics of plasmonic MEMS infrared light source selected frequency and optical radiation enhancement,this will provide a theoretical basis and technical support for the application of MEMS infrared gas sensor.The main research contents and results in this paper are as follows:1.We investigated MDPhC combined structure with TDMSHA and silicon-air photonic crystal,and explored the ratio of the horizontal geometry namely hole radius ratio to the array period(r/a₀=0.2,0.25,0.3) effect on the EOT performance at metal/air interface surface plasmon polaritons(SPP)(1,0) ground-state model of MDPhC.Based on the design and production of the gold/silicon dioxide/silicon MDPhC structure by our MEMS group,we used FDTD numerical simulation to the structure and measured reflectance spectra of experimental samples.Comparing with square lattice round hole array,it is found that both the theoretical simulation results and the experimental results have proved that MDPhC being composed of triangular lattice round hole array,while r/a₀=0.25,it can obtain better effect of light transmission enhancement and narrower transmission peak.The relationship(λ_min=1+0.82a₀) of array period(a₀) and the minimum reflectivity position(λ_min) by fitting the theoretical simulation results and the relationship(λ_min=0.2+0.94a₀ ) by fitting the experimental results are the same linear relationship basically.This linear relationship is coincident with the equation(λ_min≈3^1/2a₀/2=0.87a₀) by the introduction of SPP coupling mechanism,it is confirmed that the SPP coupling mechanism to explain the EOT characteristics of MDPhC is feasible.2.We investigated M/MDPhC combined structure with double-layered metallic films,which the metal film's thickness of outer layer is less than its skin depth and the metal film's thickness of the inner layer is much larger than skin depth.It is found that the role of SPP mutual coupling occurs between the double-metal of the structure.The effect of metal thickness(t_m) at outermost layer on the EOT characteristics of M/MDPhC was explored by us.We design and fabricate M/MDPhC combined structure with silver/gold double-layered metallic films' TDMSHA and silicon-air photonic crystal using MEMS technology.We used FDTD numerical simulation to the structure and measured transmission spectra of experimental samples.By comparing the EOT characteristics of M/MDPhC and MDPhC,it is found that the transmission efficiency[T(λ_max)]of SPP(1,1) hypo-state model at metal/air interface of M/MDPhC is bigger than MDPhC,and it has nothing to do with t_m;and the T(λ_max) of SPP(1,0) ground-state model at metal/air interface of M/MDPhC has something to do with t_m;it is;demonstrated that the SPP mutual coupling role being between silver/gold double-layered metallic films occurs only at metal/air interface. The results are found that:The EOT characteristics of M/MDPhC being composed of triangular lattice and square lattice round hole arrays with different silver film's thickness(t_m=1.5,3.8,23nm) exists the similar relationship with t_m.(1)With the increase of t_m,theλ_max shift to the direction of short-wavelength regularly;(2)While t_m=3.8nm,M/MDPhC has bigger T(λ_max).3.We investigated M/D/MDPhC combined structure with metal/dielectric/metal trilayer combination membrane,the effect of refractive index of dielectric on the EOT characteristics of SPP(1,0) ground-state model at metal/air interface of M/D/MDPhC was explored by us,and at the same time we also discussed the impact of the different dielectric film's thickness(t_d=0.2,0.4,0.6μm).We design and fabricate M/D/MDPhC combined structure with TDMSHA consisting of Au/SiO_xN_y/Au three combination membrane and silicon-air photonic crystal using MEMS technology.We measured transmission spectra of experimental samples.By comparing the EOT characteristics of M/D/MDPhC and MDPhC,it is found that the transmission peak of M/D/MDPhC get much narrower,it is demonstrated that the SPP mutual coupling role between Au/SiO_xN_y/Au three combination membrane indeed exists.The results are found that:(1)λ_max of M/D/MDPhC being composed of SiO_2.1N_0.3 with small refractive index(1.6) is smaller than that of M/D/MDPhC being composed of SiO_0.6N₁ with large refractive index(1.8),the phenomenon can validate the correctness of SPP mutual coupling role mechanism;(2)M/D/MDPhC being composed of dielectric SiO_2.1N_0.3 with small refractive index has a larger T(λ_max) and a narrower transmission peak;(3)M/D/MDPhC being composed of SiO_xN_y with thin film(0.2μm) is able to get much larger T(λ_max) and narrower transmission peak; With the increase of SiO_xN_y film's thickness,theSPP(1,0) ground-state model at metal/air interface of M/D/MDPhC gradually degrades,and its transmission peak also gradually widens.