Spectroscopic study of semiconductor materials used for solar cells with an apparatus assembled at NREL from components of many suppliers. An ultrafast laser measures the azimuthal dependence of second-harmonic generation in a spontaneously ordered GaInP thin film. Atomic ordering, a form of bandgap engineering used at the National Renewable Energy Laboratory's Basic Sciences Center, results in a change to the crystal symmetry of the material. This is revealed in the second-order nonlinear susceptibility, which can identify crystal directions that are isotropic to linear measurements. Spectroscopic laser (red beam) being used to measure properties of a semiconductor thin film used in solar cells. Solar cells use semiconductors to convert the energy in sunlight into electrical energy. The semiconductor thin film being investigated here, consists of a combination of the elements gallium, indium and phosphorus (GaInP0.