Sensitivity characterization of a photomultiplier tube for terahertz radiation

In this work, we present the first sensitivity characterization of a photomultiplier tube (PMT) for the detection of terahertz (THz) radiation. The PMT holds a metasurface-based photocathode that emits electrons via the electron field emission effect. This leads to a very non-linear detector that allows one to see much smaller variations of an incident signal than the absolute signal strength itself. We find that this particular PMT has a detection threshold for a THz pulse of 1 nJ and a detection confidence level of 99.7% within 55 – 250 pJ, depending on the THz pulse energy.