Abstract: Optical nano-antennae have been integrated with semiconductor lasers to intensify light at the nanoscale and photodiodes to enhance photocurrent. In quantum optics, plasmonic metal structures have been used to enhance nonclassical light emission from single quantum dots. Absorption and detection of single photons from free space could also be enhanced by nanometallic antennae, but this has not previously been demonstrated. Here, we use nano-optical transmission effects in a one-dimensional gold structure, combined with optical cavity resonance, to form optical nano-antennae, which are further used to couple single photons from free space into a 80-nm-wide superconducting nanowire. This antenna-assisted coupling enables a superconducting nanowire single-photon detector with 47% device efficiency at the wavelength of 1550 nm and 9-μm-by-9-μm active area while maintaining a reset time of only 5 ns. We demonstrate nanoscale antenna-like structures to achieve exceptional efficiency and speed in single-photon detection.

Abstract: Materials with a small superconducting energy gap favor a high detection efficiency of low-energy photons in superconducting nanowire single-photon detectors. We developed a TaN detector with smaller gap and lower density of states at the Fermi energy than in comparable NbN devices, while other relevant parameters remain essentially unchanged. This results in a reduction of the minimum photon energy required for direct detection to $\approx1/3$ as compared to NbN.

Abstract: We present the results of stability testing of a terahertz radiometer based on a superconducting receiver with a SIS tunnel junction as the mixer and a flux-flow oscillator as the local oscillator. In the continuum mode, the receiver with a noise temperature of 95 K at 510 GHz measured over the intermediate frequency (IF) passband of 4-8 GHz offered a noise equivalent temperature difference of 10 ± 1 mK at an integration time of 1 s. We offer a method to significantly increase the integration time without the use of complex measurement equipment. The receiver observed a strong signal over a final detection bandwidth of 4 GHz and offered an Allan time of 5 s.

Abstract: Terahertz multi-pixel heterodyne receivers introduce multiple challenges for their implementation, mostly due to the extremely small dimensions of all components and even smaller tolerances in terms of alignment, linear dimensions and waveguide component surface quality. In this manuscript, we present a concept of terahertz multi-pixel heterodyne receiver employing optical layout using polarization split between the LO and RF. The frontend isbased on a waveguide balanced HEB mixer for the frequency band 1.6 – 2.0 THz. The balanced HEB mixer followsthe layout of earlier demonstrated APEX T2 mixer. However for the mixer presented here, we implemented split-block layout offering inimized lengths of all waveguides and thus reducing the associated RF loss. The micromachining methods employed for producing the mixer housing and the HEB mixer chip are very suitable for producing multiple structures and hence are in-line with requirements of multi-pixel receiver technology. The demonstrated relatively simple mounting of the mixer chip with self-aligning should greatly facilitate the integration of such multi-channel receiver. Index Terms—Instrumentation, Multi-pixel, Terahertz, Waveguide Balanced Mixer.