Qi-jun Yao

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The terahertz and far-infrared band, ranging from approximately 0.3 THz to 15 THz (1 mm to 20 μm), is important for astrophysics as it hosts the peak of the thermal radiation of the cold component of the Universe as well as many spectral lines that trace the cycle of interstellar matter1–8. However, water vapour makes the terrestrial atmosphere opaque to(More)
Thanks to its high frequency, THz wave is very suitable for ultra-broadband and high data rate communications. Because transmission of THz signal is seriously affected by atmosphere, especially water vapor, more sensitive THz detection techniques are essential for efficient and long-distance THz communications. Based on 0.5THz superconducting SIS receiver,(More)
We introduced here a compact 500GHz SIS (Superconductor-Insulator-Superconductor) heterodyne receiver system developed for POST (POrtable Sub-millimeter Telescope). The system is proved to have a small volume to be integrated with the small Dewar, which is cooled by a compact close-cycled 100mW@ 4K cryo-cooler. Test results shows that a good LO(More)
China is planing to construct a 5-m THz telescope (DATE5) at Dome A, Antarctic, which is the best site on the earth for astronomical observations in the THz regime. To evaluate the atmospheric transmission at Dome A, we have developed a broadband Fourier transformer spectrometer for 0.75~15 THz (Dome A FTS). The details of the instrument and measurement(More)
This paper mainly presents the frequency and temperature characteristics of a W-band attenuator, which include the correlation of signal frequency to attenuation and ambient temperature to attenuation respectively. Since the attenuation has dependence on input frequency and ambient temperature, the investigation on these characteristics is helpful to the(More)
Atroposelective synthesis of axially chiral biaryls by palladium-catalyzed C-H olefination, using tert-leucine as an inexpensive, catalytic, and transient chiral auxiliary, has been realized. This strategy provides a highly efficient and straightforward access to a broad range of enantioenriched biaryls in good yields (up to 98 %) with excellent(More)
A simple imaging system operating at 0.5 THz band, utilizing nearly quantum-limited sensitive NbN superconductor-insulator-superconductor (SIS) mixers, is demonstrated. The system is proved to have a spatial resolution of 2.7 mm and sensitivity of 1.6 K with a 100 mm diameter collecting Teflon lens. The results show that this imaging modality is applicable(More)
POST was developed cooperatively by the Purple Mountain Observatory and the National Astronomical Observatory of Japan from 1997 to 2000 [1]. Performance degradation occurred in the POST system after years of operation. So a through upgrade was carried out in 2014, which include hardware and software of the control system, servo system, bias supply power,(More)
A fast terahertz vector field measurement system based on the on-the-fly (OTF) scan method is investigated. Compared with the step scan method, which samples at certain step, the OTF scan obtains the data with the scanner moving continuously, thus improving the measurement efficiency to some extent. The phase stability of the system is fully studied.(More)
We demonstrate for the first time the integration of a superconducting hot electron bolometer (HEB) mixer and a quantum cascade laser (QCL) on the same 4-K stage of a single cryostat, which is of particular interest for terahertz (THz) HEB/QCL integrated heterodyne receivers for practical applications. Two key issues are addressed. Firstly, a low power(More)