Title :
Performance of all-NbN quasi-optical SIS mixers for the terahertz band
Author :
Uzawa, Yoshinori ; Kawakami, Akira ; Miki, Shigehito ; Wang, Zhen
Author_Institution :
Commun. Res. Lab., Kansai Adv. Res. Center, Kobe, Japan
fDate :
3/1/2001 12:00:00 AM
Abstract :
We have designed, fabricated, and tested terahertz superconductor-insulator-superconductor (SIS) mixers having a self-compensated NbN/AlN/NbN tunnel junction and an epitaxially grown NbN/MgO/NbN microstripline. The junction as a distributed element was 0.8-μm wide and 2.4-μm long, and its current density was 50 kA/cm 2. The microstripline consisted of a 200-nm-thick NbN ground plane, a 180-nm-thick MgO insulator, and a 350-nm-thick NbN wiring layer. An investigation of the mixer in our receiver configuration showed flat noise characteristics from 870 to 960 GHz. The lowest receiver noise temperature of about 550 K was obtained at 909 GHz, including a 9-μm-thick Mylar beam splitter loss and other optical losses. These characteristics suggest that SIS mixers with self-compensated NbN/AlN/NbN junctions and NbN/MgO/NbN microstriplines are appropriate for used in wideband and low-noise operations at terahertz frequencies
Keywords :
aluminium compounds; current density; microstrip circuits; niobium compounds; submillimetre wave mixers; submillimetre wave receivers; superconducting device noise; superconducting device testing; superconducting microwave devices; superconductor-insulator-superconductor mixers; 0.8 mum; 2.4 mum; 870 to 960 GHz; Mylar beam splitter loss; NbN ground plane microstripline; NbN-AlN-NbN; NbN-MgO-NbN; NbN/AlN/NbN quasi-optical SIS mixers; current density; distributed element junction; epitaxially grown NbN/MgO/NbN microstripline; flat noise characteristics; optical losses; receiver configuration; receiver noise temperature; self-compensated NbN/AlN/NbN tunnel junction; superconductor-insulator-superconductor mixers; terahertz band; wideband low-noise operations; Automatic testing; Current density; Josephson junctions; Microstrip; Optical losses; Optical noise; Optical receivers; Superconducting device noise; Superconducting devices; Superconducting epitaxial layers;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
