All-optical Thermo-optic Switch Based On Low-dimensional Nanomaterial Thin Film

Since the discovery of graphene,new two-dimensional materials such as transition metal dichalcogenides?TMDs?have attracted widespread attention due to their unique photonic and electronic properties.Meanwhile,all-optical switches play an important role in all-optical signal processing and communications.The realization of all-optical devices based on the ultrafast optical properties and large optical nonlinearities of 2D materials has become a major research direction in ultrafast all-optical signal processing.In this thesis,we mainly demonstrate a thermo-optic all-optical switch using nanomaterial thin film.In the first chapter,a summary of the research background of this thesis was reviewed,and the research status of graphene,black phosphorus?BP?and TMDs in all-optical devices has been investigated.This thesis focuses on thermo-optic all-optical devices,and synthesizes the typical research results of various teams in recent years on thermo-optic all-optical devices based on nanomaterials.Then we give the starting point and significance of this thesis.In chapter two,the principle of all-optical modulation based on nanomaterial was introduced,including three aspects:non-linear effect,carrier effect and thermo-optic effect.The polarization interference structure in thermo-optic effect is mainly introduced.In the third chapter,the preparation and characterization experiments of TMDs were studied.Several common preparation methods of TMDs were introduced.Nanomaterial film was prepared by Liquid Phase Exfoliation method.The physical and optical properties of the nanomaterial film were measured,and it was verified that the molybdenum disulfide-polyvinyl alcohol?MoS₂-PVA?thin film has wavelength dependent absorption characteristic.In the fourth chapter,we investigated an all-optical switch using MoS₂-PVA thin film based on the thermo-optic effect and obtain a long-time stable modulated output by applying polarization interference.We also analyzed and discussed the response speed and stability of the switching signal.In addition,an all-optical switch based on WSe₂-PVA thin film has also been demonstrated.In chapter five,in order to further improve the performance of the switching signal,we studied the all-optical switch based on carbon nanotube-polyvinyl alcohol?CNT-PVA?thin film and obtained the signal with low input power and fast switching speed.Finally,a summary of this thesis expounds the innovation and the future research direction.We believe our work may pave the way for exploring 2D nanomaterials for more potential in all-optical signal processing.