Encyclopedia … combined with a great Buyer's Guide!

Single-mode Operation

Definition: operation of a laser on axial (longitudinal) resonator modes only, or even on a single axial mode

Opposite term: multimode operation

German: einmodiger Betrieb

Category: laser devices and laser physics


How to cite the article; suggest additional literature

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

The term single-mode operation, which usually applies to lasers, is ambiguous, as it is used with different meanings:

spectra of laser emission
Figure 1: Emission spectra of lasers with single-mode emission (top), multiple axial mode (but single transverse mode) emission (middle), and full multimode emission (bottom).

The number and type of oscillating resonator modes in a laser depends on the circumstances:

  • The excitation of higher-order transverse modes can often be avoided by pumping only the volume covered by the axial modes. This is often done e.g. in end-pumped solid-state lasers.
  • Multiple axial modes may still be excited, if the gain bandwidth is larger than the axial mode spacing (as is the case in most solid-state lasers). This may be changed by inserting an intracavity filter (e.g. an etalon), or by increasing the axial mode spacing (free spectral range), i.e. by using a very short laser resonator.

Single-frequency operation is usually more difficult to achieve than just single-transverse-mode operation because it is not sufficient to introduce spatially varying loss or gain. Factors which make it more challenging are all those reducing the mode competition, e.g. inhomogeneous saturation via spatial hole burning.

See also: diffraction-limited beams, Gaussian beams, beam quality, single-frequency lasers, single-frequency operation, resonator modes, mode competition, modes of laser operation

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.


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

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

Code for Links on Other Websites

If you want to place a link to this article in some other resource (e.g. your website, social media, a discussion forum, Wikipedia), you can get the required code here.

HTML link on this article:

<a href="https://www.rp-photonics.com/single_mode_operation.html">
Article on Single-mode operation</a>
in the <a href="https://www.rp-photonics.com/encyclopedia.html">
RP Photonics Encyclopedia</a>

With preview image (see the box just above):

<a href="https://www.rp-photonics.com/single_mode_operation.html">
<img src="https://www.rp-photonics.com/previews/single_mode_operation.png"
alt="article" style="width:400px"></a>

For Wikipedia, e.g. in the section "==External links==":

* [https://www.rp-photonics.com/single_mode_operation.html
article on 'Single-mode operation' in the RP Photonics Encyclopedia]