Photoreflectance (PR) is a powerful, contactless, and nondestructive technique capable of probing interband electronic transitions and built-in electric-fields at the surface and in interface regions in semiconductor materials and microstructures. It has been widely used as a characterization tool. However, its application to highly luminescent systems, such as quantum-well (QW) lasers and samples with poor surface morphology has been limited because of the difficulty in minimizing the interference from the luminescence and the pump beam that is scattered from the surface. We present a double modulation procedure where both the probe and pump beams are modulated which allows the PR component to be completely separated from the luminescence and scattered contributions. The separation is achieved through the appropriate choice of modulation frequencies and specially designed tuned amplifiers. A complete PR system, along with the necessary circuits, is presented. In addition, we have also exploited the freedom provided by the system to choose any pump wavelength to selectively modulate specific regions of the multilayer structure (QW, barrier, and cladding layer) and extract detailed information regarding the properties of each layer. The applicability of the procedure is demonstrated by fully characterizing a GaInP based QW laser structure used for visible emitters and by measurements on a saw-cut and chemically etched back surface of a commercial GaAs wafer. Finally, procedures attempted in the past to overcome difficulties with the luminescence and surface scattering are discussed and compared to the double modulation PR technique.