Fiber-Coupled 2-D n-i-pn-i-p Superlattice Photomixer Array

We have fiber-coupled an array of n-i-pn-i-p superlattice photomixers using a fiber array of same pitch of 145 μm. We experimentally investigate the effect of the finite size of the implemented silicon lens on the interference between the array elements in the far field. We compare the results from a geometry optimized for a collimated terahertz (THz) beam to theory and simulations. Further, beam steering is demonstrated by controlling the optical phase of the individual photomixers. Due to broadband antennas attached to each array element, the array is frequency tunable. It is exemplarily characterized at 165 and 310 GHz. Such arrays can overcome power limitations of individual photomixers. In contrast to bulky individually packaged free space solutions, this array can be packaged to a compact terahertz source, limited in size only by the size of the silicon lens. The investigated 2 × 2 array features a spot diameter (full-width at half-maximum) of 12.1 mm at a distance of 19 cm at 310 GHz with a silicon lens of only 20-mm diameter.