Study On High-speed Terahertz Modulation Based On Photomixers And Terahertz Filters

With property of lardge bandwidth, compact, high anti-interference, terahertz radiation holds great promise for short-range wireless communication, satellite communication and secret communication. Modulation, filtering and control of terahertz wave are the key elements for the development of terahertz infromation technology. However, the study on terahertz communication technology is still in its infancy, and many key challenges remain to be solved. Transferring high frequency signals onto terahertz carrier is just one of the matters of urgent doubt.In this dissertation, a high-speed terahertz modulation scenario based on terahertz photomixers is designed. Two gigahertz rate Mach-Zehnder modulators are used to amplitude modulating the laser beams of the photomixer. To intuitively analysing the results, some numerical simulation results are given out. Transfer of modulating signals onto terahertz radiation is demostrated both by theoretical analysis and numerical simulation. The modulation bandwidth is very lardge and only limited by the modulators in the simulations. The modulation depth of 100% can be realized on this modulation scheme.Terahertz filters are another key device in terahertz communication. By transmission matrix method, terahertz filtering properties of one dimention photonic crystal is studied. The effection on terahertz transmission peak of the thickness, refrective index and extinction coeffienct of the defact layer is analyzed through numerical simulation. Tuning of terahertz transmission peak by varying the thickness, refractive index or extinction coeffienct of the defact layer is demonstrated. And a terahertz switch based on liquid crystal material with high perfromance is also proposed.