Bandwidth-limited Pulses | previous | next | feedback |
Definition: pulses with a duration as short as possible with their optical spectrum
A bandwidth-limited optical pulse (or transform-limited pulse) is a pulse which is as short as its spectral bandwidth permits. In other words, its time–bandwidth product is as small as possible.
A slightly different definition for a bandwidth-limited pulse is that its peak power is as high as the optical bandwidth allows (for a given pulse energy). This is equivalent to the pulse having a flat spectral phase, and normally also leads to the shortest possible pulse duration.
Figure 1: Optical bandwidth of sech2-shaped bandwidth-limited pulses. Different curves apply for different center wavelengths due to the conversion from frequency to wavelength intervals.
If an initially transform-limited pulse propagates through a medium, its time–bandwidth product can increase due to the influences of chromatic dispersion or nonlinearities. For example, the influence of dispersion can temporally stretch the pulse while leaving its spectral width constant. This is associated with a chirp. This chirp can later be removed by dispersive pulse compression, restoring the original pulse duration.
Many mode-locked lasers, particularly soliton mode-locked solid-state lasers, but also some mode-locked diode lasers, can generate nearly bandwidth-limited pulses. This feature is very desirable e.g. in optical fiber communications, as it minimizes dispersive temporal broadening.
See also: time–bandwidth product, pulses, chirp, pulse compression
Since October 2008, 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.
