saturable

Saturable is an adjective used in science and engineering to describe a system whose response to an external stimulus tends toward a finite maximum rather than increasing without bound as the stimulus grows. In such systems, the relationship between input and output is nonlinear and often described by a saturation curve, where the incremental response diminishes at higher inputs.

In magnetism, saturable refers to materials that exhibit magnetic saturation: as an external magnetic field increases, the material's magnetization approaches a maximum value (the saturation magnetization). Beyond this point, further increases in field produce only small changes in magnetization. Saturable materials are used in devices such as saturable inductors and saturable reactors, which exploit the nonlinear permeability of ferromagnetic cores to perform regulation or pulse shaping.

In optics, saturable absorbers are materials whose optical absorption decreases with increasing light intensity. At low intensities they absorb strongly, but as intensity grows the absorption saturates and becomes more transparent. They are widely used to enable passive mode-locking or Q-switching in lasers, and practical implementations include semiconductor saturable absorber mirrors, graphene, carbon nanotubes, and organic dyes.

In surface and adsorption science, adsorption can be described as saturable when available binding sites on a surface are finite; under high concentration the amount adsorbed approaches a maximum value consistent with adsorption isotherms such as Langmuir models.

See also: saturation, saturation magnetization, saturable absorber, saturable reactor, Langmuir isotherm.