A paper on ultrafast THz detectors based on 3D meta-atoms has been published in Optica by the group at University of Paris South. Quantum-well infrared photodetectors (QWIPs) have proved to be an excellent technology as ultrafast THz receivers, given their intrinsic picosecond-range response. However, with research focused on diffraction-limited QWIP structures (λ∕2), RC constants cannot be reduced indefinitely, and detection speeds are bound to eventually meet an upper limit. The key to an ultra-fast response with no intrinsic upper limit even at tens of gigahertz (GHz) is an aggressive reduction in device size, below the diffraction limit. Here we demonstrate sub-wavelength (λ∕10) THz QWIP detectors based on a 3D split-ring geometry, yielding ultra-fast operation at a wavelength of around 100 μm. Arrays of detectors as well as single-pixel detectors have been implemented with this new architecture, with the latter exhibiting ultra-low dark currents below the nA level. This extremely small resonator architecture leads to measured optical response speeds—on arrays of 300 devices—of up to ∼3 GHz and an expected device operation of up to tens of GHz, based on the measured S parameters on single devices and arrays.
The full publication can be accessed here