ErAs:GaAs photomixer with two-decade tunability and 12 μ W peak output power

This letter reports the fabrication and demonstration of an ErAs:GaAs interdigitated photomixer as a tunable THz source ranging from ∼ 20 GHz to ∼ 2 THz , with 12 μ W maximum power typically around ∼ 90 GHz . Each photomixer is coupled to a composite dipole-spiral planar antenna that emits a Gaussian-type beam into free space. The beam switches from dipole to spiral antenna behavior as the frequency increases. A distributed Bragg reflector is embedded in the device beneath the photomixer to increase its external quantum efficiency. The photomixer has a 900 Å thick silicon nitride coating which serves as an antireflection and passivation layer, and also improves the reliability and heat tolerance of the device.