Interaction of Terahertz Radiation with Semiconductor Lasers

Terahertz (THz) technology bears great potential in spectroscopy, imaging, material science, security screening and high-speed wireless communication. However, the generation of intensive, directional THz radiation has been difficult and the THz frequency range has long been considered the last final frontier of the electromagnetic spectrum. Recent advancement in optoelectronic terahertz generation techniques and high power electronic sources has helped to bridge the THz gap and has opened up a wealth of new applications for THz technology. However, there is still a major technical limitation in developing THz systems for mass markets, mainly due to the cost of THz hardware components including sources and detectors. In this regard, we investigated the use of semiconductor diode lasers as THz detectors as well as excitation sources for photomixers for THz generation. For THz detection, we investigated the interaction of semiconductor lasers with THz radiation. Intense THz radiation from different sources and at various frequencies was injected into the laser diode. The laser diode was operated in Littman configuration to ensure clean single mode operation in the near infrared. The charge carrier system in the semiconductor was expected to interact with the injected THz radiation and introduce nonlinear frequency mixing. This nonlinear mixing was to induce sidebands in the near infrared optical spectra and was to be analyzed with an optical spectrum analyzer. This may lead to the demonstration of a simple, cost effective and compact room temperature THz spectrometer since the distance between the emission line and the sidebands equals the incident THz frequency. Unfortunatly, due to unprecedented challenges the interaction of THz radiation with diode laser experiment was not successful.