Photon noise is the randomness in signal associated with

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always ...

s arriving at a detector. For a simple

black body A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The name "black body" is given because it absorbs all colors of light. A black body ...

emitting on an absorber, the

noise-equivalent power Noise-equivalent power (NEP) is a measure of the sensitivity of a photodetector or detector system. It is defined as the signal power that gives a signal-to-noise ratio of one in a one hertz output bandwidth. An output bandwidth of one hertz is equi ...

is given by :

\mathrm^2 = 2 h^2 \nu^2 \Delta\nu \left( \frac + n^2 \right)

where

h

is the

Planck constant The Planck constant, or Planck's constant, is a fundamental physical constant of foundational importance in quantum mechanics. The constant gives the relationship between the energy of a photon and its frequency, and by the mass-energy equivale ...

\nu

is the central frequency,

\Delta\nu

is the bandwidth,

n

is the

occupation number In quantum mechanics, a Fock state or number state is a quantum state that is an element of a Fock space with a well-defined number of particles (or quanta). These states are named after the Soviet physicist Vladimir Fock. Fock states play an impo ...

and

\eta

is the optical efficiency. The first term is essentially

shot noise Shot noise or Poisson noise is a type of noise which can be modeled by a Poisson process. In electronics shot noise originates from the discrete nature of electric charge. Shot noise also occurs in photon counting in optical devices, where shot ...

whereas the second term is related to the

boson In particle physics, a boson ( ) is a subatomic particle whose spin quantum number has an integer value (0,1,2 ...). Bosons form one of the two fundamental classes of subatomic particle, the other being fermions, which have odd half-integer s ...

ic character of photons, variously known as "

Bose Bose may refer to: * Bose (crater), a lunar crater * ''Bose'' (film), a 2004 Indian Tamil film starring Srikanth and Sneha * Bose (surname), a surname (and list of people with the name) * Bose, Italy, a ''frazioni'' in Magnano, Province of Biella ...

noise" or "wave noise". At low occupation number, such as in the

visible spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' or simply light. A typical human eye wil ...

, the shot noise term dominates. At high occupation number, however, typical of the

radio spectrum The radio spectrum is the part of the electromagnetic spectrum with frequencies from 0 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particula ...

, the Bose term dominates.

References

* * *

See also

References

Further reading