Research On Surface Plasmon Nanostructures For Infrared Detection Enhancement

In the field of nanophotonics,surface plasmon nanostructures are able to manipulate light efficiently on the sub-wavelength scale,and their surface plasmon resonance effects can not only propagate in the form of surface plasmon polaritons,increasing the optical path of light in materials,but also form localized surface plasmon resonance effect,producing significant near-field enhancement effect.The unique optical properties of surface plasmon nanostructures can be employed to effectively increase the optical absorption and responsivity of devices,which offers an opportunity to improve the performance of detectors.The first part of research work focused on the detection enhancement effect of metal gratings with propagating surface plasmon polariton effect in InAs/GaSb superlattice mid-infrared photodetectors.The finite element method was employed to investigate and compare the optical absorption characteristics of the device without and with surface plasmon grating arrays,and the physical mechanism behind was discussed.At the meantime,the influence of grating structure parameters on the optical absorption of devices were compared and analyzed,which provided a new direction and method for the design of surface plasmon enhanced photodetectors.In the second part of research work,the detection enhancement effect of localized surface plasmon nanostructures in the near-infrared wavelength region was investigated.The localized surface plasmon resonance properties of anisotropic nanostructures—silver nanoplates were theoretically studied.The results show that by changing the size,thickness and the refractive index of the surrounding medium of metal nanostructures,their resonant peaks can be effectively covered in the infrared wavelength regime.Under the guidance of theoretical design,silver nanoplates were prepared by the employment of seed growth method,and the shape and size of silver nanoplates were under good control.Moreover,two-dimensional material MoS₂ photodetectors were fabricated and the electrical characteristics of devices were tested.Then,in combination with self-assembly technology,the experimental study of surface plasmon enhanced two-dimensional material photodetectors was explored,which provided an experimental support for the preparation and test of surface plasmon enhanced two-dimensional material detectors.In the third part of research work,to broaden the range of tunable resonant peaks of localized surface plasmon nanostructures and meet the demand of detection enhancement at longer wavelength,the optical properties of hollow silver nanoplates were further simulated and investigated.The simulation results show that by changing the thickness and cavity size of hollow silver nanoplates,the surface plasmon resonant peaks can be tunable in the infrared wavelength regime.And the FWHM of hollow silver nanoplates was obviously smaller than that of silver nanoplates,which can be used for narrow-band detection enhancement.In addition,hollow silver nanoplates can be employed as refractive index sensor,their refractive index sensitivities are as high as 1333 nm/RIU,and the figure of merit can reach 9.52.