Second Harmonic Generation (SHG) can be used to interrogate a surface of a sample such as a layered semiconductor structure. The SHG based sample interrogation systems may simultaneously collect different polarization components of the SHG signal at a time to provide different types of information. SHG imaging systems can provide SHG images or maps of the distribution of SHG signals over a larger area of a sample. Some such SHG imaging systems employ multiple beams and multiple detectors to capture SHG signals over an area of the sample. Some SHG imaging systems employ imaging optics to image the sample onto a detector array to form SHG images.