Above:
QCD array assembly showing the lens array to couple radiation and the detector array.
QCD
Seeing a Single Photon
Pierre Echternach
Far-infrared spectroscopy can reveal secrets of galactic evolution and heavy-element enrichment throughout cosmic time and astronomers worldwide are designing cryogenic far-IR space telescopes. The most challenging aspect is a far-IR detector that is both exquisitely sensitive, limited by the zodiacal-light noise in a narrow band (λ/Δλ ~ 1000), and arrayable to tens of thousands of pixels. The quantum capacitance detector (QCD) being developed in MDL is a 50 mK device adapted from quantum computing applications in which photon-produced free electrons in a superconductor, tunnel into a small capacitive island embedded in a resonant circuit. The QCD has demonstrated optically-measured noise equivalent power (NEP) of 2x10-20 W Hz-1/2 at 1.5THz under 10-19 W of optical loading, making it the most sensitive far-IR detector ever demonstrated. The QCD has further demonstrated individual far-IR photon counting, confirming its exquisite sensitivity and suitability for cryogenic space astrophysics.
This text appeared in an article in Nature Astronomy and more details are given in the paper.
P. M. Echternach, B. J. Pepper, T. Reck, C. M. Bradford (2018) Single photon detection of 1.5 THz radiation with the quantum capacitance detector. Nature Astronomy2, 90–97. doi.org/10.1038/s41550-017-0294-y
One pixel of a lumped element mesh absorber QCD used to demonstrate single photon detection of 1.5THz radiation.
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