Research On The Novel Tunable Terahertz Modulator Of Black Phosphorus

Black phosphorus is a direct band gap semiconductor with a layer-controlled band gap and its monolayer lattice structure is an orthogonal lattice with folded structure composed of phosphorus atoms.The excellent optical and electrical properties of black phosphorus make the application of black phosphorus in photoelectric devices have a broad prospect.However,monolayer black phosphorus has a very low absorption rate and very weak interaction with light.It is of great significance to enhance the interaction between the light and black phosphorus.The monolayer and bilayer graphene-black phosphorus band absorbers in the mid-infrared band are proposed by using the perfect plasmon absorbers.Therefore,the absorption of the proposed structure is higher than 90%in mid-infrared.The hybrid of graphene and black phosphorus can increase the absorption of black phosphorus to more than 80%in mid-infrared.The dual-band absorption of the double-layer graphene-black phosphorus absorber structure can also be independently tuned by the material parameters of graphene and black phosphorus.Moreover,the absorption spectrum of the proposed structures are independent of the angle of the incident light.In the terahertz band,a tunable terahertz modulator based on the perfect absorber of black phosphorus plasmons is proposed by using the slit enhanced absorption model.Since the slit model in the structure can significantly enhance the interaction between black phosphorus and terahertz waves,the proposed two-dimensional modulator structure can achieve up to 95%modulation depth and 1.7 THz resonance frequency modulation offset.The physical mechanism of the slit reinforcement effect was further explored by the electromagnetic field distribution.Through a series of numerical simulations,the effect of slit width and height on the performance of the modulator is obtained.In order to extend the application of the modulator to different terahertz frequency bands,the working frequency of the modulator can be tuned by changing the width of the silver ribbon.When the width of the silver ribbon changes within a certain range,the resonant frequency of the modulator will correspondingly generate a certain offset,which can meet the application requirements of different terahertz frequency bands.