Ultrafast Optical Modulation Of Dipole Arrays At Terahertz Frequencies

Terahertz, as a kind of precious resource, has attracted much attention all over the world. But it is difficult to have electromagnetic response using the natural materials in terahertz region. So compared with the development of THz sources and detectors, the manipulation of terahertz wave technology is laggard. The application of subwavelength periodic array of metal structure will be the best candidate for manipulation of terahertz, and will promote the development of communications. The amplitude modulation and phase modulation are regarded as one of the most important feature of metamaterisals. It can work at different frequency of course the terahertz region by change its size and shape. Moreover, the method of active control to metamatierial can open up their applications in modulation and switching. It is therefore important to know the response of metamaterials to external perturbation and understand the underlying physical mechanism. So we investigated the dynamical behavior of optical modulation in the "I" and "L" metamaterials at different pump power using optical pump-terahertz probe spectroscopy. The experimental results show the feasibility of optical modulation, and it will be widely used in the field of radar imaging, sensing and communications.The main issues in this essay include the following points:1.Study of dipole arrays based on Si substrate. Studies have shown that more sensitive with increase in the dipole length. Moreover, Si will not be used as the substrate of metamaterial.2.Study of the effect on resonant amplitude of terahertz transmission and phase at different pump power about GaAs as well as dipole arrays based on GaAs substrate.3.Study of the effect on resonant amplitude of terahertz transmission and phase at different pump power with double-dipole sample based on GaAs substrate.4.Study of split-"L" at different orientations based on GaAs substrate.5.Study of the characteristics of "L" samples. The current distribution is different from that of split-"L".