CW-photomixing semiconductor devices have hardly exceeded an output power of 10 μW around 1 THz.
Availability of a few mW, however, would stimulate the demand for THz-imaging, -scanning, and spectroscopy.
Increasing the poor power conversion efficiency from the optical pump to THz-output is most
desirable. On the other hand, the thermal threshold "per pixel" is limited to about 100 mW of pump laser
power. So both limits have to be pushed towards higher performance. In this paper
we report on arrays of photomixing devices to overcome the thermal threshold limit.
If each individual photomixer in the array can be driven to the same thermal threshold power,
the overall THz output can be larger by a factor N\times M for an array. The power of directed emission,
however, can be increased even by a factor (N x M)2 compared to the individual device.
In addition, by adjusting the two laser beams slightly noncollinear, a directional control of the
emitted THz-beam is achieved. The angular difference of the incident beams is
enhanced by the ratio of the THz-wavelength (≈300 μm) and the optical wavelength (≈0.85 μm)
with regard to direction of the emitted THz-beam. Thus, a full steering of the THz beam
can be achieved by tuning this angle by less than 1 degree (17.5 mrad).