| Terahertz(THz)is an electromagnetic wave with a frequency range of 0.1-10 THz.Because of its unique electronic and photonics characteristics,it is widely used in the fields of astronomy,remote sensing,imaging and security.Especially in the field of wireless communication,terahertz band has become one of the best choices to improve the bandwidth and rate of the sixth generation wireless mobile communication.Due to the low power of terahertz radiation source,the application of terahertz technology is limited.One of the most commonly used methods to generate terahertz wave is photoconductive antenna,which has the advantages of room temperature operation,compact design and broadband radiation.However,the traditional photoconductive antenna is only composed of substrate and electrode.The low light absorptivity and photocurrent lead to the low terahertz radiation power,which greatly limits its application range.To solve this problem,this paper combines the surface plasmon characteristics of metal with photoconductive antenna,designs a high absorptivity nanorod photoconductive antenna structure and nano ring photoconductive antenna structure,improves the electrode structure of traditional photoconductive antenna,and simulates it by finite difference time domain method,It is expected to provide a new idea and feasible design scheme for the development of photoconductive antenna in the future.The main content of this paper is:1.A novel equilateral triangular array of nanorods photoconductive antenna structure is designed.The structure adds a gold nanorod array at the electrode gap of the bow-tie photoconductive antenna.The array is arranged in an equilateral triangle and the substrate is semi insulated Ga As.On the one hand,the new triangle aligned gold nanorod array structure concentrates the incident beam locally between the arrays,on the other hand,due to surface plasmon resonance,the nanostructure enhances the light absorption of the substrate.The simulation results show that this structure is helpful to improve the photocurrent in the terahertz emitting photoconductive layer.Compared with the bow-tie photoconductive antenna,the optical absorptivity is increased by 269%,the electric field intensity is increased by 1294%,and the photocurrent is increased by 156%.2.A novel nano ring photoconductive antenna structure is designed,which improves the nanorod array into a nano ring array to further enhance the light trapping effect of the nanostructure and then enhance the light absorption of the photoconductive antenna.The results show that the optical absorption of this structure is more than 93%,which is 4%higher than that of nanorod photoconductive antenna structure.The research results provide a valuable reference for realizing the high power conversion efficiency of terahertz photoconductive antenna.3.A novel triangular array electrode photoconductive antenna structure is designed,and the influence of electrode structure on nanostructured photoconductive antenna is analyzed.The new triangular array antenna electrode structure is composed of five triangular tips,which increases the area of laser incident on the substrate and reduces the transmission distance of optical carriers.At the same time,compared with the traditional and bow-tie electrode structures,the triangular array structure increases the number of triangular tips,which leads to more charges gathering at the electrode tip,and the charge accumulation at the tip leads to a stronger electric field,which greatly improves the light absorption of the structure.At the same time,the effects of different electrode thickness and light spot position on the triangular array photoconductive antenna are studied.The final absorptivity is increased to 40%,which is 211% and 160% higher than that of traditional electrode and bow-tie electrode photoconductive antenna,respectively.The triangular array electrode structure provides a new idea for the electrode structure design of photoconductive antenna. |
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