Room temperature ultrafast InGaAs Schottky diode based detectors for terahertz spectroscopy

Abstract

The design and characterisation of rectifying terahertz detectors, based on InGaAs zero-bias Schottky diodes, is reported. These uncooled devices offer a spectral detection range from tens of GHz to above 3 THz, high response speed, and the prospect of low cost for mass production and arrayed implementation. We describe the airbridged semiconductor devices, their incorporation into waveguide mounts and quasi-optical substrate lens/planar antenna structures. Noise equivalent powers of 5 pW/Hz1/2 at 100 GHz, increasing to 50 pW/Hz1/2 at 300 GHz been achieved, along with rise and fall times of tens of picoseconds. We shall discuss examples of the use of the detectors: characterising a picosecond transistor-based source, spectrally narrow and broad band sources in the laboratory and coherent THz synchrotron radiation in the range 0.15–1.4 THz at the MIRIAM beamline B22 on the Diamond Light Source. The latter radiation was emitted from bunches of electrons circulating in the Diamond storage ring operating in THz-dedicated low-alpha mode. Spectral information on coherent synchrotron radiation originating from a single bunch of electrons is obtained, as well as the usefulness of this for spectroscopy, is evaluated.