text: The name "photo-reflectance" or "photoreflectance" is shortened from the term "photo-modulated reflectance," which describes the use of an intensity modulated light beam to perturb the reflectance of a sample. The technique has also been referred to as "modulated photo-reflectance," "modulated optical reflectance," and "photo-modulated optical reflectance." It has been known at least since 1967.