A novel terahertz detector technology based on vacuum electronics

A THz detector with both high sensitivity and fast time response has been required for industrial applications such as nondestructive testing (NDT), security, and spectroscopy. Through a collaboration with the Technical University of Denmark (DTU), we have recently developed a THz-sensitive point detector and imager based on metasurface and photomultiplier tube (PMT) and image intensifier (I.I.) technologies, respectively. A fast time response is one of the unique characteristics of these devices: the PMT-based point detector provides a nanosecond response time while the I.I.based imager is capable of frame rates up to 1000 fps. These devices have a double split-ring resonator (DSRR) at the photocathode for THz-electron conversion (metasurface). In this paper, we discuss the two devices and report on the development and results for increasing their sensitivity for ultrafast, broadband THz pulses by sharpening the field-enhancing antenna tips. This leads to a smaller tip diameter, which increases the electric field confinement and thus intensity at the tip, making the field emission more likely to occur at lower field strengths as a result. Both devices thus offer a sensitive and simple method to detect THz frequencies easily, with the I.I. offering a handheld, 9V battery-powered device.