Encyclopedia … combined with a great Buyer's Guide!

Sponsors:     and others


Definition: a measure of the strength of optical amplification

More specific terms: small-signal gain, laser gain, Raman gain

German: Verstärkung, Verstärkungsfaktor

Categories: laser devices and laser physics, optical amplifiers

Formula symbol: g, G

Units: %, dB or dimensionless number

How to cite the article; suggest additional literature


URL: https://www.rp-photonics.com/gain.html

In photonics, the term gain is usually used to quantify the amplification of optical amplifiers or of a laser gain medium. Different meanings occur in the literature:

  • The gain can simply be an amplification factor, i.e., the ratio of output power and input power.
  • Particularly for small gains, the gain is often specified as a percentage. For example, 3% correspond to a power amplification factor of 1.03.
  • Particularly large gains are often specified in decibels (dB), i.e., as 10 times the logarithm (to base 10) of the amplification factor. For example, a fiber amplifier may have a small-signal gain of 40 dB, corresponding to an amplification factor of 104 = 10 000.
  • One also often specifies a gain per unit length, or more precisely the natural logarithm of the amplification factor per unit length, or alternatively the decibels per unit length.

Apart from its magnitude, important properties of gain are its spectral bandwidth and its saturation characteristics.

The gain achieved e.g. in a fiber amplifier or the gain medium of a laser depends on the population densities in different electronic levels, which themselves depend on the optical intensities. Rate equation modeling may be used for calculating the gain and investigating its dependence on various influences.

Questions and Comments from Users

Here you can submit questions and comments. As far as they get accepted by the author, they will appear above this paragraph together with the author’s answer. The author will decide on acceptance based on certain criteria. Essentially, the issue must be of sufficiently broad interest.

Please do not enter personal data here; we would otherwise delete it soon. (See also our privacy declaration.) If you wish to receive personal feedback or consultancy from the author, please contact him, e.g. via e-mail.

Your question or comment:

Spam check:

  (Please enter the sum of thirteen and three in the form of digits!)

By submitting the information, you give your consent to the potential publication of your inputs on our website according to our rules. (If you later retract your consent, we will delete those inputs.) As your inputs are first reviewed by the author, they may be published with some delay.


[1]R. Paschotta, tutorial on "Fiber Amplifiers", part 2 on gain and pump absorption

(Suggest additional literature!)

See also: laser gain media, gain bandwidth, gain clamping, optical amplifiers, fiber amplifiers, gain saturation, gain narrowing, gain switching, gain efficiency, homogeneous saturation, inhomogeneous saturation
and other articles in the categories laser devices and laser physics, optical amplifiers


Share this with your friends and colleagues, e.g. via social media:

These sharing buttons are implemented in a privacy-friendly way!