Currently superconductors are used for Terahertz telescope detects but new graphene terahertz detectors will use less than 0.1% of the power. Instead of microwatts, the graphene detectors could use 0.1 nanowatts. If a superconducting detector could produce a single pixel then new graphene detectors could have 1000 to 10000 pixels.
Above – The image depicts a schematic of terahertz (THz) heterodyne detection with graphene. In this, two THz waves (red) are coupled into graphene, where they are combined or mixed. One of the waves is a high intensity signal generated by a local THz light source (i.e. a local oscillator), at a known THz frequency. The other signal is a faint THz wave that mimics the waves coming from space. Illustration: Hans He
Observations in the terahertz (or the far-infrared) frequency range (100GHz-10THz) are of great importance for understanding physics and chemistry in the star and planet forming regions. With the wavelength in THz range much longer than that in the IR, terahertz waves have capacity to reveal processes hidden behind dusty gas clouds. Space born telescopes allow overcoming severe atmospheric absorption, whereas a diverse park of instrumentation permits to cover a wide range of scientific tasks. To recover information carried by faint celestial signals, THz frequency mixers -the core of coherent detection- have to fulfill stringent requirements on both sensitivity and, more importantly, on bandwidth, to enable line surveys and studying Doppler-stretched molecular lines. Superconducting hot-electron bolometer (HEB) mixers form the baseline for modern astronomical receivers above 1 THz.
Space telescopes were the first application for CCD detectors in the 1970s and 1980s. Now CCD detectors are used for the cameras on your cellphone. Terahertz technologies for medical applications, remote sensing, and manufacturing are already being developed.
Spectacular advances in heterodyne astronomy with both the Herschel Space Observatory and Stratospheric Observatory for Far Infrared Astronomy (SOFIA) have been largely due to breakthroughs in detector technology. In order to exploit the full capacity of future THz telescope space missions (e.g. Origins Space Telescope), new concepts of THz coherent receivers are needed, providing larger bandwidths and imaging capabilities with multi-pixel focal plane heterodyne arrays. Here we show that graphene, uniformly doped to the Dirac point, enables highly sensitive and wideband coherent detection of THz signals. With material resistance dominated by quantum localization, and thermal relaxation governed by electron diffusion, proof-of-concept graphene bolometers demonstrate a gain bandwidth of 8 GHz and a mixer noise temperature of 475 K, limited by residual thermal background in our setup. An optimized device will result in a mixer noise temperature as low as 36 K, with the gain bandwidth exceeding 20 GHz, and a Local Oscillator power lower than 100 pW. In conjunction with the emerging quantum-limited amplifiers at the intermediate frequency, our approach promises quantum-limited sensing in the THz domain, potentially surpassing superconducting technologies, particularly for large heterodyne arrays.