The Fabrication And Optical Sensing Application Of Large-area Silicon Photonic Crystal Metasurfaces

In recent years,metasurfaces have become one of the fastest growing fields in nanophotonics.Metasurfaces are sub-wavelength scale nanostructures composed of metals or high refractive index dielectric materials that can be used to design functional devices in ultrathin forms.The plasmon metasurface composed of metal micro-nano structure mainly relies on the local plasmon effect of metal micro-nano structure to realize the regulation of light.It provides powerful optical resonance,enabling applications in beam diverters,holograms,and high-resolution color printing.However,one of the most obvious limitations of plasmon metasurfaces is the high optical loss,which reduces the overall performance of the device and limits many practical applications.At the same time,electron beam lithography(EBL)and focused ion beam(FIB)techniques are commonly used to prepare various small-scale metasurface optics in research experiments.However,for the preparation of largescale devices in the future,the above technology has the disadvantages of high cost and long processing time.How to achieve the preparation of large-scale and high-performance optical devices is a major problem at present.Based on the above problems,how to achieve low-cost and large-scale device fabrication.In this paper,a combination of soft nanoimprint lithography(SNL)and reactive ion etching(RIE)is proposed to prepare large-area photonic devices.Different from the traditional processes EBL and FIB to achieve the preparation of small-scale nanostructures,SNL technology can realize the preparation of high-throughput,large-area nanostructures.By controlling the etching conditions,10 new nanostructures can be obtained based on one original seal,and metasurface resonances can be effectively tuned over a wide range.An iterative embossing and etching method is also proposed to further reduce the minimum size of metasurfaces,thereby improving the quality of smaller structures.Experiments show that this method can achieve large-scale amplification of nanostructures without affecting the resolution of nanoscale,and reduce the cost of experiments.Dielectric metasurface devices in the optical continuum domain bound state(BIC)have attracted widespread attention because their optical losses are much smaller than plasmon metasurfaces.By exciting the quasi-BIC resonance mode,near-field enhancement and high-quality factors can be greatly achieved.Based on this principle,in the second research work,the large-area silicon-based photonic crystal device with high quality factor was prepared by the above method.Combining simulation and experiments,it is found that the introduction of transverse and vertical dimension changes during the etching process stimulates the quasi-BIC mode in the photonic crystal and enables the preparation of photonic devices with the highest quality factor of 136.We calculated its ultra-high sensitivity for refractive index sensing to be 1703 nm/RIU.The device observes good spectral movement when detecting glucose solution concentration changes and adsorption of monolayer silane molecules.This method enables low-cost fabrication of large-area,high-performance quasiBIC devices,which enables future realistic optical sensing applications.In summary,aiming at the challenge of how to prepare large-scale and high-performance optical devices in the field of nanophotonics,this paper proposes a combination of SNL and RIE process methods to achieve the preparation of large-area,low-cost and high-resolution silicon-based photonic devices with high Q values.It is expected to promote the development of nanophotonic devices and applications in the field of optical sensing.