Colliding pulse modelocked lasers for terahertz photomixing

THz time domain spectroscopy systems (TDS) have been finding their way into the market quite recently. Most of these systems use a laser source delivering ultra short laser pulses into a homodyne detection scheme based on photomixers. These sources are usually characterized by pulse lengths below 200fs, bandwidths of several THz and round trip frequencies / repetition rates below 1GHz. All in all this gives remarkable results in terms of signal to noise ratio in the frequency range up to 4THz. But, unfortunately, these sources are also the main cost factor in such THz TDS systems which hampers the possibilities for mass applications.