fotonflux

Fotonflux is a measure of the flow of photons through a surface, defined as the number of photons crossing the surface per unit area per unit time. It is used in optics, photonics, solar energy, and photochemistry to describe light in terms of photon counts rather than radiant power.

The photon flux density is typically denoted Φ and has units of photons per square meter per second (photons/m^2/s). If a light source delivers total optical power P onto an area A, and each photon has energy E = hν = hc/λ, then the photon flux density is Φ = Ṅ/A = P/(hν) = Pλ/(hc) when using spectral data. For broadband light, the total photon flux is obtained by integrating over the spectrum: Ṅ = ∫ Pν/(hν) dν or Ṅ = ∫ Pλ/(hc/λ) dλ, with corresponding flux densities Φν = Pν/(hν) and Φλ = Pλ λ/(hc).

Spectral forms are common: Φν = Pν/(hν) [photons m^-2 s^-1 Hz^-1] and Φλ = Pλ λ/(hc) [photons m^-2 s^-1 nm^-1]. The total flux follows from appropriate integration over the wavelength or frequency range of interest.

Measurement and practical use: photon flux can be inferred from calibrated radiometric measurements using known photon energies, or directly measured with photon-counting devices and integrating spheres for total flux. In applications such as photovoltaics and photochemistry, photon flux relates to reaction rates and quantum yields, while in lighting and illumination design it informs spectral performance and efficiency considerations.

Fotonflux provides a spectral-aware alternative to radiant power for evaluating light-driven processes.