We demonstrate concepts for compact and cost effective THz technology based on semiconductor diode lasers. In detail,
we analyze diode laser based THz sources and detectors. Continuous wave THz radiation is generated by two color diode
lasers either with external photomixers or direct difference frequency generation in the diode laser. For time domain THz
sampling applications we present a suitable mode-locked diode laser system. Further we present a method to detect THz
radiation with diode lasers at room temperature: A THz signal coupled into the active region of a diode laser results in a
variation of the voltage across the p-n-junction.
In this paper we discuss three different techniques to generate THz radiation at room temperature with semiconductor
lasers. The state of the art is to generate the THz radiation by photomixing of two optical modes in
a photoconducting antenna. We show that the complexity of this setup can be reduced by using a laser system
emitting two colors simultaneously. Optical power is in excess availiable by using an optical amplifier. In a second
approach we demonstrate, that the complexity and cost of the setup can be significantly reduced, by generating
the THz radiation directly in the two color laser. This is realized by making use of nonlinear processes in the
carrier system. While all these methods generate cw radiation, we finally suggest a third approach to generate
pulsed THz radiaton with semiconductor lasers. This THz source can be used in THz time domain systems.
The emission spectrum of a two-color semiconductor laser is analyzed. We find four-wave mixing sidebands for difference frequencies up to 4 THz. The appearance of four-wave mixing signals is a clear sign for a modulation of the carrier plasma at the corresponding difference frequency. We prove experimentally that this difference frequency is also directly emitted out of the laser diode and suggest a new simple concept for the generation of tunable coherent THz-radiation.