Laser linewidth is the spectral linewidth of a laser beam. More precisely, it is the width of the power spectral density of the emitted electric field in terms of frequency, wavenumber or wavelength. The laser linewidth is related to its temporal coherence that is characterized by the coherence time or coherence length. Single frequency lasers are most often described as narrow bandwidth lasers because single frequency lasers oscillate on a single resonator mode with low phase noise resulting in low phase noise.
In order to achieve a narrow emission bandwidth from a laser, several issues need to be resolved. First of all, as mentioned above, single-frequency operation needs to be achieved. The main goal is to avoid mode hopping. Secondly, external noise levels must be minimized, therefore a stable resonator setup with protection against mechanical vibrations is required. Fiber lasers should have a pump source with low-intensity noise; moreover, any optical feedback should also be avoided. Ideally, the external noise will become lower than internal noise. Lastly, the laser should be designed with a narrow bandwidth in mind. The design of the narrow bandwidth laser should be optimized so that the laser noise and phase noise are minimized.
The problem of noise characterization and specification arises during the production of narrow bandwidth lasers. This issue is particularly prominent for linewidth values of a few kilohertz or less. There are a number of measurement techniques for noise specification available for laser manufacturers and researchers.
Narrow bandwidth lasers, including narrow bandwidth fiber lasers, are required for numerous different applications. One of the fields of application is the area of sensors. Fiber-optic sensors, like FBG strain sensors, FBG temperature sensors, LIDAR, wind speed measurements, etc. require narrow bandwidth lasers. Another area of application is optical frequency metrology. It requires very narrow bandwidth that is frequently achieved with stabilizers. Optical fiber communicators also demand narrow bandwidth lasers, however, the requirements are usually less demanding.
Optromix manufactures laser systems of outstanding quality and reliability. We are always happy to configure your laser according to your unique needs.
If you would like to buy narrow bandwidth fiber lasers, please contact us at: info@optromix.com or +1 617 558 9858
