Electromagnetic radiation in the mid-infrared portion of the spectrum is critical for sensing and spectroscopy. However, detecting mid-infrared radiation is challenging. Typically, mid-infrared detectors rely on photon absorption in exotic semiconductor structures, or they use relatively slow (low-bandwidth) thermal effects. Here, we demonstrate the detection of long-wave infrared laser pulses in metal-semiconductor-metal photodiode structures. The pulses span the spectral range from 7-12 microns and have pulse energies <1 nJ. Our detectors consist of gold and titanium nanoantenna emitters resting on an intrinsic silicon substrate and separated by sub-micron gaps from collector electrodes. Operating at room temperature, our detectors yield >2 μA currents and exhibit bandwidths exceeding 1.3 GHz.
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