Research On Terahertz Source Via Liquid Crystal Grating Coated With Graphene

Terahertz wave is a kind of electromagnetic wave with frequency between 1 and 10 THz,which has been paid more and more attention in recent years.Because of the single photon energy is much lower than that of X-ray,it not produces photoionization on the human body,no damage to human cells.Images can produce according to the strength of the terahertz wave,it has a great application prospect in medical and security.Today,big data transmission for high carrier frequency and high transmission rate has a very high demand,terahertz wave has a high penetration,good security and other advantages.It also has great potential in communication and military.Among them,the study of terahertz source is very important.Gas lasers,semiconductor lasers and free electron lasers have been developed.Relatively speaking,some can not be continuously tuned,the average power is low and not conducive to its detection,some devices are bulky,high cost and power consumption.These are not conducive to scientific research and commercial use.Therefore,the tunable,large power,small equipment,low cost terahertz source must be solved.The main contents of this paper include:1.Compared to the previous research results of terahertz sources,explains the principle of the terahertz source based on graphene.Necessary discussion is given about surface plasmon of graphene,application of liquid crystal birefringence properties,the mechanism of Smith-Purcell radiation and electrical tuning method.2.The Maxwell's equations with boundary conditions are rigorously solved to calculate the the radiation``` and the dispersion relationship of the structure.The radiation energy is calculated by using the principle of conservation of energy.It is concluded that the radiation frequency is proportional to the radiation energy.3.We the deflection angle of liquid crystal and the velocity of electron beam.In order to avoid the difficulty of changing the Fermi level,we tune the radiation frequency by controlling the effective refractive index of the liquid crystal by voltage.