Defect detection in saturable absorbers

Technologies are generally described for identifying defects in saturable absorbers, such as graphene, by the saturable property of decreasing light absorbance with increasing light intensity. For example, a graphene coated substrate may be imaged twice under two distinct incident intensities. At a gap in the graphene, the substrate may reflect light proportional to the incident intensities. The graphene may show a non- linear increase in reflected light as the intensity of illumination increases. A difference between the two incident intensities may reveal the gap in the graphene. Any suitable imaging technique may be employed such as confocal microscopy or linear scanning. The imaging may be scaled up for high volume automated inspection.