Saturation intensity The saturation intensity IS is defined as the input intensity at which the gain of the optical amplifier drops to exactly half of the small-signal gain. We can compute the saturation intensity as where is the Planck constant, and is the saturation time constant, which depends on the spontaneous emission lifetimes of the various transitions between the energy levels related to the amplification. is the frequency in Hz The minimum value of occurs on resonance, where the cross section is the largest. This minimum value is: For a simple two-level atom with a natural linewidth , the saturation time constant .
Saturation intensity The saturation intensity IS is defined as the input intensity at which the gain of the optical amplifier drops to exactly half of the small-signal gain. We can compute the saturation intensity as where is the Planck constant, and is the saturation time constant, which depends on the spontaneous emission lifetimes of the various transitions between the energy levels related ,to the amplification. is the frequency in Hz The minimum value of occurs on resonance, where the cross section is the largest. This minimum value is: For a simple two-level atom with a natural linewidth  the saturation time constant .