We present the experimental demonstration of a quasioptical terahertz (THz) detector. It is based on the series connection of three Nb 5 N 6 microbolometers. This detector is of high responsivity and broadband response to THz signals. The maximum optical responsivity is 428 V/W at 0.245 THz and the minimum is 102 V/W at 0.367 THz. The thermal time constant of the detector has been demonstrated to be 1.3 μs, which is similar to the ones obtained for single-element microbolometers. These results make arrays of antenna-coupled Nb 5 N 6 microbolometers promising for the development of pixels in THz focal-plane arrays.
Using millimeter-wave spectroscopy, we study the electromagnetic response of asymmetric split-ring resonators made from superconducting niobium. The asymmetry is introduced by using different arm lengths of the U-shape split-ring design. A small asymmetry allows the excitation of an otherwise dark mode with only a weak coupling to electromagnetic field. The radiation losses are strongly reduced in this geometry. The combination of weak electromagnetic coupling and reduced ohmic losses in a superconductor leads to high quality factors of split-ring resonators. Quality factors of up to 150 in an open design are achieved experimentally.
Localized plasmon modes are excited and probed in a large-area grating-gate GaN/AlGaN high-electron-mobility transistor structure embedded in a Fabry-Pérot cavity using a terahertz time-domain spectroscopy (THz-TDS) at cryogenic temperature. Determined by the length of grating finger and the electron concentration, the frequency of localized plasmon modes can be continuously tuned by the gate voltage in the spectral range from 0.1 THz to 1.5 THz. When the plasmon frequency is tuned to be in resonance with the terahertz Fabry-Pérot cavity mode, a strong coupling between the plasmon mode and the cavity mode is observed and the terahertz plasmon-polaritons are formed in such a cavity-coupled two-dimensional electron system. The electromagnetic simulations have confirmed the strong coupling between them.
Onto a double layer, which is made of a Si substrate ( ρ> 1000 Ω·cm ) and a SiO2 layer 100 nm thick
on top of it, a Nb5N6 thin film microbridge is deposited and integrated with an aluminum bow-tie
planar antenna. With a SiO2 air-bridge further fabricated underneath the microbridge and operated
at room temperature, such a combination behaves very well as a bolometer for detecting signals at
100 GHz, thanks to a temperature coefficient of resistance (TCR) as high as -0.7% K-1 of the Nb5N6 thin film. According to our estimations, the best attainable electrical responsivity of the bolometer is
about -400 V/W at a current bias of 0.4 mA. The electrical noise equivalent power (NEP) is 6.9x10-11 W/Hz1/2 for a modulation frequency at 300 Hz and 9.8x10-12 W/Hz1/2 for a modulation frequency
above 10 kHz respectively, which are better than those of commercial products (such as Golay cell
and Schottky diode detectors). A quasi-optical receiver based on such a bolometer is constructed and
Conference Committee Involvement (5)
Infrared, Millimeter-Wave, and Terahertz Technologies VII
12 October 2020 | Online Only, China
Infrared, Millimeter-Wave, and Terahertz Technologies VI
21 October 2019 | Hangzhou, China
Infrared, Millimeter-Wave, and Terahertz Technologies V
12 October 2018 | Beijing, China
Infrared, Millimeter-Wave, and Terahertz Technologies IV
12 October 2016 | Beijing, China
Infrared, Millimeter-Wave, and Terahertz Technologies III