Difference frequency generation of infrared waves in asymmetric quantum wells

There has been a great deal of interest in recent years in the investigation of signals in the terahertz frequency range of the electromagnetic spectrum. One impediment to this ongoing research is the lack of useful sources of energy and detectors in this spectral region. One promising solution to this problem is the use of non-linear optics and the process of difference frequency generation (DFG). This dissertation investigates the use of DFG in dielectric waveguide structures utilizing the resonant enhancement of asymmetric quantum wells.; The AlxGa(1-x)As/GaAs material system was investigated for this approach. Samples were grown in a molecular beam epitaxy chamber and characterized via photoluminescence and Raman spectroscopy to verify their composition. A series of investigations was conducted in homogenous waveguide structures utilizing a laser diode mixed with a tunable Ti:sapphire solid state laser. Both waveguide and non-linear phase matching were investigated and demonstrated.; The large second order non-linear susceptibility of GaAs can be enhanced utilizing asymmetric quantum wells. The theory behind this enhancement and the utility of utilizing structures of this nature in waveguides designed for DFG processes was investigated.; Phase matching in waveguide structures was investigated. This involves not only the non-linear phase matching requirements, but the waveguide mode requirements. It was found that a waveguide structure can be used to lower the effective index of refraction of the dielectric material, and as such can contribute to non-linear phase matching. Procedures were developed for simplifying the calculation of guided mode waveguide structures which contain multi-layers such as quantum wells. It was found that guided mode phase matching in such structures is extremely difficult, and that no cross mode solutions exist.; Finally, a novel approach to conducting DFG with a single laser source was developed and investigated. The laser is operated in a pulsed mode, and the problem of pulse coherence in the waveguide structure was investigated and solved. It was found that even with the relatively higher energy of the Ti:sapphire source, that the phase matching condition could not be achieved. Sources of the mismatch are discussed and proposals for future work presented.