Characteristic Research On Optically And Electrically Controlled Terahertz Metamaterials

The rise of metamaterials brings new development opportunities for terahertz technology moving towards mature applications,especially the active metamaterials whose functions and properties can be modulated dynamically have become the research hotspots in the terahertz regime.In this thesis,we studied several works around the optically and electrically controlled terahertz devices,as listed below: 1? we concluded the confronted challenges and problems at present through introducing the research scope and practical value of terahertz technology,and elaborated that active metamaterials are important and effective for breaking the technical limitations.In allusion to the achievements of three active devices studied in this thesis,we introduced the relative theoretical model to fit and explain the electromagnetic responses,sample fabrications and detailed process,and the design of optical pump terahertz probe system based on tilted pulse front excitation.2? The design and performance measurement of an optically controlled broadband plasmonic induced transparency(PIT)metamaterial was demonstrated in this thesis.Composed of a central bar and four U shaped rings,the enhanced coupling between multiple dark modes and bright mode led to broadband PIT effect.Fabricated on SOS substrate,the device achieved the optical switching effect with the bandwidth from 0.54 to 0.82 THz by planting the silicon pattern artfully.Started from coupled Lorentz oscillator model,the active modulation was ascribed to the limitation of resonance excitation for four U shaped rings as the role of dark mode.3? The dynamic near-mode coupling in a terahertz metamaterial was presented.The electromagnetic response of three different dimensional and concentric square rings was simulated by CST,the coupling between adjacent rings led to strongly transmitted peak and opposite surface current.By planting the photosensitive silicon into the adjacent square sing,the dynamic modulation was achieved through changing the conductivity of silicon in simulation and varying the pump power in the measurement,making the mode coupling translate capacitive to conductive.Started from coupled Lorentz oscillator model,the active modulation originated from the variation of the damping rate and coupling coefficient of the resonance modes.4? An electronical controlled metasurface terahertz deflector with phase discontinuities was studied.Comprised of eight complementary C-shape SRR with identical transmission amplitude and equal phase increment of ?/4,the device enabled the anomalous diffraction with bandwidth from 0.48 to 0.93 THz for orthogonal polarization.The formation of a Schottky diode structure between the metal film and doped Ga As substrate achieved the intensity modulation of the deflected wave.The modulation depth and speed could reach to 46% and 3k Hz,respectively.The simulation operating by changing the conductivity of Ga As substrate showed the accordant with the experiments very well.