Coherent addition
Encyclopedia
Coherent addition of laser
s
is one of methods of the power scaling
. It allows a to increase the output power and brightness of single-transversal mode
laser.
Usually, the term coherent addition applies to fiber laser
s. As the ability of pumping and/or cooling of a single laser is saturated, several similar lasers can be forced to oscillate in phase with common coupler.
The coherent addition was demonstrated in power scaling
of Raman laser
s .
of the spectral bandwidth of gain and/or length of partial lasers.
The same conclusion can be made also on the base of more detailed simulations.
Practically, the combination of more than ten lasers in such a way should be difficult if at all.
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
s
is one of methods of the power scaling
Power scaling
Power scaling of a laser is increasing its output power without changing the geometry, shape, or principle of operation. Power scalability is considered an important advantage in a laser design....
. It allows a to increase the output power and brightness of single-transversal mode
Transverse mode
A transverse mode of a beam of electromagnetic radiation is a particular electromagnetic field pattern of radiation measured in a plane perpendicular to the propagation direction of the beam...
laser.
Usually, the term coherent addition applies to fiber laser
Fiber laser
A fiber laser or fibre laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, and thulium. They are related to doped fiber amplifiers, which provide light amplification without lasing...
s. As the ability of pumping and/or cooling of a single laser is saturated, several similar lasers can be forced to oscillate in phase with common coupler.
The coherent addition was demonstrated in power scaling
Power scaling
Power scaling of a laser is increasing its output power without changing the geometry, shape, or principle of operation. Power scalability is considered an important advantage in a laser design....
of Raman laser
Raman laser
The Raman laser is a byproduct of Raman scattering, discovered in 1928 by Nobel laureate Chandrasekhara Venkata Raman and Kariamanickam Srinivasa Krishnan in liquids and independently by Grigory Landsberg and Leonid Mandelshtam in crystals. When light hits a substance, it causes the atoms in the...
s .
Limits of coherent addition
The addition of lasers reduces the number of longitudinal modes in the output beam; the more lasers are combined, the smaller is the number of longitudinal modes in the output. The simple estimates show that the number of output modes reduces exponentially with number of lasers combined. Of order of eight lasers can be combined in such a way. The future increase of number of combined lasers requires the exponential growthExponential growth
Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...
of the spectral bandwidth of gain and/or length of partial lasers.
The same conclusion can be made also on the base of more detailed simulations.
Practically, the combination of more than ten lasers in such a way should be difficult if at all.