Theoretical Study On Enhancing Terahertz Radiation

Sandwiched between millimeter wave and infrared light, terahertz radiation owns many unique features enabling ample potential applications, however, restricted by lacking an effective high-power THz radiation source. Therefore, it is of huge practical significance to do theoretical researches on enhancing THz radiation.Recently, many researchers focus their efforts on experimental study on enhancement of THz radiation from semiconductor surfaces in a magnetic field. There does not exist a complete theory able to explain many experimental observations.This thesis employs Drude-Lorentz model to analyze the motion of photogenerated carriers in the semiconductor depletion region under the influence of both built-in electric field and applied magnetic field. We then deduce analytical expressions of electrical field, power, and power enhancement factor of TE and TM mode THz radiation in a magnetic field.This thesis discusses and analyzes the effects, on enhancing THz radiation, of laser incident angle, direction and intensity of a magnetic field, temperature, and semiconductor's material features. We conclude that InSb and InAs are promising candidates for enhancement study of THz radiation. The saturation radiation power from the InSb surface under a 0.2 T magnetic field at 100 K is at least two orders of magnitude higher than that without a magnetic field at room temperature.In addition, we also get several conclusions as follows: 1) Power of TM mode THz wave reaches a maximum when laser incident angle nears the Brewster angle;2) THz radiation power has a quadratic dependence on low magnetic field and saturates at a high magnetic field;3) THz radiation power saturates more quickly at a lower magnetic field as temperature decreases;4) The semiconductor material owning smaller electron effective mass and higher electron mobility contributes to a higher THz power enhancement factor saturating more fast in a magnetic field.