Buff Clamp

The definition of gain clamping is a strict restriction on the gain of certain amplifiers or lasers, usually caused by laser action.

When the pumping power (optical or electrical) of the laser gain medium increases, it usually results in an increase in the resulting optical gain. However, in some cases, the gain is tightly bound to a precisely defined value, which cannot be exceeded even if the pump power is greatly increased. The gain is precisely clamped to the value of the optical resonator loss, and any increase in gain results in an exponential increase in laser power, which is clearly inconsistent with steady-state conditions. The gain achieved by this mechanism is much more accurate than gain saturation at high pump power.

In lasers and amplifiers (e.g., fiber amplifiers), gain clamping limits not only the optical gain, but also the excitation density (upper energy-state density). This, in turn, limits the strength of stored energy and other effects, such as quenching processes or excited state absorption.

Gain clamping is sometimes used in fiber amplifiers to stabilize the optical gain, where laser light is emitted at certain wavelengths outside of the signal wavelength range, which can be achieved by incorporating a fiber Bragg grating into the device. Fluctuations in pump or signal power will have only a small impact. Note, however, that gain clamping only stabilizes steady-state gain, and transient phenomena can still occur, such as rapid changes in pump or signal input power.