Degree Name

Doctor of Philosophy


Institute for Superconducting and Electronic Materials


Due to a previous lack of suitable sources and detectors, terahertz (1012 Hz) frequencies have proven to be historically inaccessible relative to the neighbouring microwave and infrared regions, where electronic and optical techniques respectively dominate. In recent years, however, the \Terahertz Gap" has been closing due to a number of novel and interesting technologies. This has sparked interest in a number of industrial and scienti c applications where terahertz frequencies have signi cant advantages over other frequencies.

In this thesis, I will focus on the generation and detection of terahertz-frequency pulses using short pulses of infrared light, using a co-ordinated system of generation and detection known as time-domain spectroscopy (TDS). With TDS, one may obtain a time-resolved electric eld measurement with sub-picosecond resolution. The fourier transform of the time-resolved signal yields both phase and amplitude spectral information over a wide spectral range simultaneously { this may be used to investigate the frequency dependence of the complex permittivity of a given sample and observe absorption lines in the terahertz region.

Several emission mechanisms will be discussed, such as photoconductive (PC) emission, transient current (TC) emission, and optical recti cation (OR) emission. These mechanisms are often present simultaneously and it may be necessary to analyse several experimental parameters to separate out the various contributions. Along with the investigation of multiple candidate emitters, I present a completely general theory for the geometry of optical recti cation in semiconductor crystals of 43m symmetry, that is, the zinc-blende class comprising III-V and II-VI semiconductors such as gallium arsenide (GaAs), indium phosphide (InP), zinc telluride (ZnTe) and others.