Study On All-optical-switching Based On Silicon-polymer Compound Metasurface

With the development of micro-nano fabrication technology,the use of artificial micro-nano structures to control the light field is a current research hotspot.Photonic crystals,metamaterials and metasurfaces are artificial micro-nano structures,which have received extensive attention in the past ten years.Artificial micro-nano structures possess many optical properties superior to natural materials and have many important applications,such as the realization of micro-nano laser light sources,optical sensing,optical holography and storage,optical communication and optical information processing devices,etc.At the chip level,the realization of optical signal transmission,manipulation and computing leading to the optoelectronic hybrid integration are expected to break the bottleneck of traditional electronic chips,and will have far-reaching significance for the development of disruptive information technologies such as artificial intelligence.The all-optical switching is the key device and technology to realize the control and optical computing of the optical signal,and the realization of the all-optical switching with high performance that can be easily integrated has attracted a large amount of attentions.The existing theoretical and experimental schemes of switching still have plenty room to develop in terms of simultaneously achieving high switching contrast,ultra-fast switching response time,ultra-low switching light intensity or switching energy,and ease of chip integration.Therefore,this thesis proposes a silicon-polymer compound metasurface for realizing all-optical switching,which is expected to achieve superior comprehensive performance.The proposed metasurface in this thesis is based on the silicon on insulator(SOI)material platform.The unit cell of the metasurface is a parallel arranged silicon double rectangular rods,and the middle position of the rectangular rod is broken.The polymer material covers the silicon metasurface and fills the voids of the double rods.We simulate the reflectance spectrum of the structure based on the finite difference time domain method.In the absence of polymer,by adjusting the structural parameters of the metasurface unit,we can obtain the reflection spectrum with the characteristics of electromagnetically induced transparent like lineshape.When covering the polymer material,the reflectance spectrum of the metasurface has a sharp asymmetric feature,which shows the characteristics of Fano resonance.The resonance wavelength of the reflection spectrum is 1.5?m,which is beneficial to the application in the field of optical communication.Previous studies have shown that conjugated polymers with high molecular weight have excellent third-order optical nonlinearities(large third-order nonlinear coefficients and femtosecond response time).We achieve the all-optical switching by changing the refractive index of the polymer material,and obtained the switching parameters with switching time of about 1 ps,switching intensity of about 800MW/cm~2,and switching contrast of 16 d B.Compared with traditional silicon-based all-optical switches,our compound material-based metasurface have superior comprehensive switching performance,and provide a feasible solution for on-chip all-optical signal processing and all-optical logic operations.