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Coulomb Blockade Photon Counter Disclosure Number: IPCOM000108436D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 41K

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Related People

Davidson, A: AUTHOR [+1]


Disclosed is a means of counting photons with submicron normalmetal tunnel junctions.

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Coulomb Blockade Photon Counter

      Disclosed is a means of counting photons with submicron
normalmetal tunnel junctions.

      It is well known that high frequency photons can be counted
using superconductive tunnel junctions, often called SIS devices.
These devices have limits caused by interference due to the Josephson
effect.  It is also well known that small area normal tunnel
junctions, which do not have any Josephson effect, can be used to
count single electrons.  Below is described a method to use small
area tunnel junctions to also count photons, without interference
from the Josephson effect.

      The method for counting photons takes advantage of the Coulomb
blockade of electron tunneling.  In the Coulomb blockade, a
normal-state tunnel junction with capacitance of the order of 10-15
farads can have very low tunnel current for applied voltages less
than e/2C, where e is the electron charge and C is the capacitance.
Therefore, if the junction is biased at a voltage slightly less than
e/2C, in the presence of a photon field, photons can be absorbed,
accompanied by the tunneling of an electron.  Measurement of the
electric current thus measures the photon flux.  The very low leakage
current of Coulomb blockade junctions at low temperature should allow
extension of photon counting to frequencies in the low GHz range.
Tunnel junctions with extremely low capacitance should also allow
extension of single photon detection upward to the THz range.