Specific detectivity

Specific detectivity, or D*, for a photodetector is a figure of merit used to characterize performance, equal to the reciprocal of noise-equivalent power (NEP), normalized per unit area.

Specific detectivity is given by $D^*=\frac{\sqrt{A}}{NEP}$, where A is the area of the photosensitive region of the detector. Its common units are $cm \cdot Hz^{1/2} / W$, also called the Jones in honor of R. Clark Jones who defined this magnitude.^[1][2]

Given that noise-equivalent power can be expressed as a function of the responsivity $\mathfrak{R}$ (in units of A / W or V / W) and the noise spectral density S_n (in units of A / Hz^{1 / 2} or V / Hz^{1 / 2}) as $NEP=\frac{S_n}{\mathfrak{R}}$, it's common to see the specific detectivity expressed as $D^*=\frac{\mathfrak{R}\cdot\sqrt{A}}{S_n}$.

The unit Jones is now commonly used with the D* figure of merit.

References and footnotes

1. ^ R. C. Jones, "Quantum efficiency of photoconductors," Proc. IRIS 2, 9 (1957)
2. ^ R. C. Jones, "Proposal of the detectivity D** for detectors limited by radiation noise," J. Opt. Soc. Am. 50, 1058 (1960), doi:10.1364/JOSA.50.001058)

 This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C".