| In recent years,surface plasmons have become an important research direction due to their properties of subwavelength and local enhancement.Subwavelength hole arrays based on metal can provide excite wave vector which can motivate surface plasmon polaritons and cause the effect of extraordinary optical transmission.Due to the characteristics of surface plasmons,extraordinary optical transmission has been widely used in optical modulation and optical sensing.The main research content of this article is studying the relationship between the structural parameters of subwavelength hole arrays with the characteristics of extraordinary optical transmission by using Finite-Difference-Time-Domain(FDTD)method.We also studied the sensing characteristics of refractive index sensor and hydrogen sensor based on subwavelength structure.In order to explore the mechanism of extraordinary optical transmission,refractive index sensor based on the structure of circular hole and annular hole,and hydrogen sensor based on circular hole with composite film were proposed respectively.The details are as follows:1.The principle of extraordinary optical transmission based on the circular、annular hole array structure with silver film and gold film are studied by simulation.The influence of structural parameters and dielectric refractive index on the characteristics of extraordinary optical transmission was investigated.The transmission spectrum of the circular hole array structure based on silver film will shift with the change of refractive index,but the sensitivity is low,only reached 186nm/RIU.Therefore,subwavelength annular hole array structure based on gold film is studied.In the refractive index range of 1.33-1.38,the sensitivity of different transmission peaks can reach 354 nm/RIU and 640 nm/RIU,respectively.2.A hydrogen sensor based on palladium/aurum(Pd/Au)composite film with circular hole array structure is simulated.The sensor is fabricated by etching circular hole array structure on a gold(45 nm)/palladium(5 nm)composite film on a silicon dioxide substrate.When the hydrogen is introduced,the palladium film will absorb the hydrogen and the dielectric constant of palladium will change,resulting in the change of incident light coupling efficiency,which is reflected in the change of transmittance.When the hydrogen concentration increases from 0% to 4%,the transmittance variation of different transmission peaks can reach 0.16 and 0.24,respectively.3.A hydrogen sensor based on palladium/metal-insulate-metal(Pd/MIM)composite film with subwavelength circular hole array is simulated.The composite film consists of palladium film(5 nm)and the MIM structure,which is composed of gold(40 nm)/silica(100 nm)/gold(40 nm)on the silicon dioxide substrate.The sensor is fabricated by etching circular hole array on the composite film of Pd//MIM.The complexity of MIM structure leads to the interaction of multiple modes such as Fabry-Perot resonance,surface plasmon polaritons,and finally results in the extraordinary optical transmission peak with narrow linewidth.When the hydrogen concentration increases from 0% to 4%,the transmittance variation of two transmission peaks can reach 0.25 and 0.2,respectively. |
