Heterodyne receivers, based on plasmonic photomixers have demonstrated high-sensitivity and broadband terahertz detection with high spectral resolution. They consist of a terahertz antenna with plasmonic contact electrodes fabricated on a photoconductive substrate. When the photomixer is pumped by two Continuous-Wave (CW) lasers with a terahertz beat frequency, the received terahertz signal by the antenna is down-converted to an intermediate frequency (IF) equal to the difference between the received terahertz frequency and optical beat frequency. The IF signal power increases quadratically with the optical pump power at low optical pump powers. However, the dependence of the IF signal on the optical pump power deviated from a quadratic behavior at high optical powers and could eventually saturate, limiting the maximum responsivity and Signal-to-Noise Ratio (SNR). We demonstrate that large area nanoantenna arrays, based on plasmonic gratings expand the device active area, raising the ceiling on optical power and, therefore, sensitivity.
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