Prior to the nonlinear absorptance test, the sample undergoes several
longitudinal scans (L-scans) at low power to position a sample surface in the pump beam.
Subsequently, Transverse (T-scan) and Time-scans are performed as a function of
peak irradiance: 3-7 irradiation levels. PCI test is
based on a spatially resolved pump-probe technique, where a low-power
probe beam detects the heating effect of an absorbed pump beam, making
it suitable for low absorption measurements.