Characters And Optical Modulation Of Terahertz Surface Plasmon Propagating In Semiconductor Surfaces

This thesis presents the theoretical work, simulation work and experimental work on the applications of surface plasmon polariton(SPP) in terahertz(THz) spectral range.Terahertz surface plasmon polaritons(THz SPPs) have the potential for applications in communications, detection and chemical analysis by exploiting their traits of being plasmonic as well as in the THz region. The modulation effect is associated with the plasma frequency of the semiconductor, which controls the propagation length of the THz SPPs through absorption. First of all, the propagation properties of THz SPPs at the flat interface of intrinsic semiconductor and air is explored. After that, the characteristic length of THz SPPs is calculated. The dispersion relations of THz SPPs? the relationship between the illuminated optical intensity and the plasma frequency of semiconductor and the characteristic surface plasmon angular frequency of semiconductor are studied by using Maxwell's equations and Drude model.Based on the theory research, the optical modulator of THz SPPs is simulated with finite element method. The transverse component of the THz SPPs electric field is explored, where a subwavelength 2-D energy confinement is observed. Two key coupling factors, the distance between razor blade and semiconductor and the angle of incoming light are analyzed.At last, terahertz time domain spectroscopy(THz-TDS) is employed to investigate terahertz spectrum with different methods of gathering information. The optical modulator of THz SPPs is set up,the excited SPPs propagate onto the semiconductor illuminated by a LED(GREE U2) source in visible spectrum range. A synthesis of studies is made to demonstrate the possibility of the new device. In comparison with traditional THz SPPs modulators based on gratings, the new device have the merits of wide modulation frequency band, large modulation amplitude, high modulation speed and low cost.Therefore, more about the transmission characters of THz SPPs propagating in semiconductors can be achieved through the research of this project. We anticipate to contribute to the development of THz industry of our country by exploring the new applications of THz SPPs.