RP Photonics logo
RP Photonics
Consulting Software Encyclopedia Buyer's Guide

Short address: rpp-con.com

Dr. Paschotta, the founder of RP Photonics, supports your R & D with his deep expertise. Save time and money with efficient support!

Short address: rpp-soft.com

Powerful simulation software for fiber lasers and amplifiers, resonator design, pulse propagation and multilayer coating design.

Short address: rpp-enc.com

The famous Encyclopedia of Laser Physics and Technology provides a wealth of high-quality scientific and technical information.

Short address: rpp-bg.com

In the RP Photonics Buyer's Guide, you easily find suppliers for photo­nics products. As a supp­lier, you can profit from enhanced entries!

Learn on lasers and photonics every day!
VL logo part of the

Propagation Constant

<<<  |  >>>  |  Feedback

Buyer's Guide

Use the RP Photonics Buyer's Guide to find suppliers for photonics products! You will hardly find a more convenient resource.

Definition: phase change per unit length for light propagating in a medium or waveguide

German: Propagationskonstante

Category: fiber optics and waveguides

How to cite the article

The propagation constant of a mode in a waveguide (e.g. a fiber), often denoted with the symbol γ, determines how the amplitude and phase of that light with a given frequency varies along the propagation direction z:

propagation constant

where A(x,y,z) is the complex amplitude of the light field.

In lossless media, γ is purely imaginary; we have γ = i β with the (real) phase constant β, which is the product of the effective refractive index and the vacuum wavenumber. Optical losses (or gain) imply that γ also has a real part.

The propagation constant depends on the optical frequency (or wavelength) of the light. The frequency dependence of its imaginary part determines the group delay and the chromatic dispersion of the waveguide.

Note that different definitions of the propagation constant occur in the literature. For example, the propagation constant is sometimes understood to be only the imaginary part of the quantity defined above, i.e., β. It is then also common to introduce a normalized propagation constant which can only vary between 0 and 1. Here, the value zero corresponds to the wavenumber in the cladding, and 1 to that in the core. Modes which are mostly propagating in the cladding will have a value close to 0.

See also: modes, effective refractive index, waveguides, fibers, group delay, dispersion

How do you rate this article?

Your general impression: don't know poor satisfactory good excellent
Technical quality: don't know poor satisfactory good excellent
Usefulness: don't know poor satisfactory good excellent
Readability: don't know poor satisfactory good excellent

Found any errors? Suggestions for improvements? Do you know a better web page on this topic?

Spam protection: (enter the value of 5 + 8 in this field!)

If you want a response, you may leave your e-mail address in the comments field, or directly send an e-mail.

If you like our website, you may also want to get our newsletters!

cover of print encyclopedia

The Encyclopedia of Laser Physics and Technology is also available in the form of a two-volume book. Maybe you would enjoy reading it also in that form! The print version has a carefully designed layout and can be considered a must-have for any institute library, laser research group, or laser company. You may order the print version via Wiley-VCH.

supercontinuum generation

Evolution of the spectrum of an ultrashort pulse in a fiber. The spectrum becomes very wide at the right end; this is called supercontinuum generation.

This diagram has been made with the RP Fiber Power software.

– Show all banners –

– Get your own banner! –