Development of a Millimeter-Long Travelling Wave THz Photomixer

THz sources based on the optical-heterodyne (photo)mixing in an ultrafast photodetector are very promising since they operate at room temperature, are potentially compact, cost-efficient and, above all, are widely frequency-tunable. However, their widespread use is currently hampered by available power levels in the μW range at THz frequencies. We present here a travelling wave structure, with millimeter level coherence length at THz frequencies opening the way to large active area (∼4000 μm 2 ) photomixing devices capable of handling optical pump power beyond 1 W well beyond the capabilities of standard lumped-element devices using small active areas (