Figure 14: Scheme of optical processes of laser modulation of two-step absorption (LM TSA) via deep centers, explaining a method of “deep level saturation spectroscopy” (DLSS). (a) Direct laser modulation of two-step absorption (-DLSS) from changes of center population by laser photoionization (). (b) Competition of - and γ-DLSS. Effect of laser "excitation-quenching" of impurity luminescence. (c) Indirect laser modulation of TSA (γ-DLSS) by capture of two-photon generated carriers.