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!
||part of the|
In the RP Photonics Buyer's Guide you can find plenty of suppliers for hundreds of photonics products.
Cut-off wavelengths and other properties of guided modes can be calculated with our free fiber optics software RP Fiber Calculator.
Definition: a wavelength above which a guided mode of a waveguide ceases to exist
The number of guided modes of a waveguide (for example, an optical fiber) depends on the optical wavelength: the shorter the wavelength, the more modes can be guided.
For long wavelengths, there may be only a single guided mode (→ single-mode fibers) or even none at all, whereas multimode behavior is obtained at shorter wavelengths.
When a particular mode ceases to exist beyond a certain wavelength, that wavelength is called its cut-off wavelength.
For an optical fiber, the cut-off wavelength for the LP11 mode sets a limit to the single-mode regime, as below that wavelength there is at least the LP01 and the LP11 mode.
Just below the cut-off wavelength, the mode properties often vary substantially.
Typically, the mode radius (and thus the effective mode area) increases sharply near the cut-off, and the fraction of power propagating within the waveguide core decreases accordingly.
That effect is shown in Figure 1 for a multimode step-index fiber; similar behavior occurs for fibers with other transverse refractive index profiles.
Fraction of the power which is contained in the fiber core as a function of the wavelength.
The thin vertical lines indicate the calculated cut-off wavelengths.
The diagram has been produced with the software RP Fiber Power.
For LPlm modes of a fiber, only for l = 0 the fraction of the power guided in the core goes to zero when approaching the cut-off.
For modes with higher l, the mode size stays finite there.
In step-index fibers, there is no cut-off for the fundamental (LP10) mode.
For other fiber designs, in particular for some photonic crystal fibers, there can also be a fundamental cut-off.
Fibers with not radially symmetric designs (and strongly bent fibers) can have polarization-dependent cut-off wavelengths.
See also: waveguides, fibers, modes, LP modes
Category: fibers and other waveguides
Have you seen the
RP Photonics Buyer's Guide?
It lists many hundreds of suppliers for photonics products, and is just one mouse click away from the extremely popular Encyclopedia of Laser Physics and Technology:
- In any product-related encyclopedia article, you find a box for the Buyer's Guide.
- Alternatively, click on the heading which your mouse pointer has just touched.
Our Buyer's Guide is what you need:
- easy handling, clear layout
- high-quality information
- additional technical information in the encyclopedia
And surely you will remember where to find this useful resource again!
Suppliers: get your free entries, and enhanced visibility with paid entries.
Tailored Training Courses
Within one or two days, a tailored training course at your location can boost the competence of your team. An investment which can pay back very rapdily!
Read a random article every day in order to steadily learn about photonics!
Free Fiber Optics Software!
RP Fiber Calculator – a convenient tool for calculations on optical fibers -- offered for free –
let us celebrate the 10-year anniversary of RP Photonics!
Beam Propagation Software
Analyze beam propagation in specialty fibers, waveguides, couplers, etc. with the new version of RP Fiber Power!