| Terahertz (THz) quantum cascade lasers (QCL) is an important kind of semiconductor radiation sources. THz waveguide propagation is also very important in the development of THz technology. In this dissertation, we study the electron transport in THz QCL, compare and discuss the waveguide property, and investigate the propagation property of THz metal wire waveguide. The result is very helpful to understand the physical mechanism and waveguide property of THz QCL. The main conclusions are as follows:1. The scattering mechanisms in THz QCL, such as electron-LO phonon scattering and electron-electron scattering have been investigated. The results show that LO phonon scattering and electron-electron scattering are probably the main scattering mechanisms in THz QCL. If the quantum well is wide, the scattering rates by confined phonons is comparable to that by interface phonons and should be taken into consideration in the calculation.2. The main waveguide design methods of THz QCL have been given and discussed by using two dimensional finite element methods. The results indicate that metal-metal waveguide has high optical confinement, low confinement factor, and small waveguide width. The doping concentration in the active region has great effect on the waveguide property. With the increasing of doping concentration, the waveguide loss, threshold gain and current density of THz QCL increase, the confinement factor decrease.3. The propagation property of THz metal wire waveguide has been investigated by numerically solving the complex eigenvalue equation. It is shown that the group velocity decreases as frequency increase, while attenuation amplitude increases with the frequency. With the increasing of metal wire radius, the group velocity and attenuation amplitude decrease. The TM mode field exponentially decreases from the interface into metal and air, respectively. In addition, the metal wire waveguide property could be modified by changing the thickness of coating layer.
|
PDF Full Text Request