Filling factor,
is a quantity measuring the efficiency of absorption of pump in the core of a
double-clad fiber
Double-clad fiber (DCF) is a class of optical fiber with a structure consisting of three layers of optical material instead of the usual two. The inner-most layer is called the ''core''. It is surrounded by the ''inner cladding'', which is surro ...
.
[D. Kouznetsov, J. V. Moloney. Highly efficient, high gain, short wavelength and power scalable incoherent diode slab-pumped fiber laser amplifier. ]IEEE Journal of Quantum Electronics
The ''IEEE Journal of Quantum Electronics'' is a peer-reviewed scientific journal covering optical, electrical, and electronics engineering, and some applied aspects of lasers, physical optics, and quantum electronics. It is published by the IEEE ...
, v.39, No.11, p.1452-1461 (2003)
Definition
The efficiency of absorption of pumping energy in the fiber is an important parameter of a
double-clad fiber
Double-clad fiber (DCF) is a class of optical fiber with a structure consisting of three layers of optical material instead of the usual two. The inner-most layer is called the ''core''. It is surrounded by the ''inner cladding'', which is surro ...
laser. In many cases this efficiency can be approximated with
:
where
:
is the cross-sectional area of the cladding
:
is the radius of the core (which is taken to be circular)
:
is the
absorption coefficient
The linear attenuation coefficient, attenuation coefficient, or narrow-beam attenuation coefficient characterizes how easily a volume of material can be penetrated by a beam of light, sound, particles, or other energy or matter. A coefficient valu ...
of pump light in the core
:
is the length of the double-clad fiber, and
:
is a
dimensionless
A dimensionless quantity (also known as a bare quantity, pure quantity, or scalar quantity as well as quantity of dimension one) is a quantity to which no physical dimension is assigned, with a corresponding SI unit of measurement of one (or 1) ...
adjusting parameter, which is sometimes called the "filling factor";