A modulated reflectance measurement system includes two diode-based lasers for generating a probe beam and an intensity modulated pump beam. The pump and probe beams are joined into a collinear beam using a laser diode power combiner. One or more optical fibers are used to transport the beams either before and/or after they are combined. The collinear beam is focused through one or more lenses or other optical components for collimation. The collinear beam is then focused by an objective lens onto a sample. Reflected energy returns through an objective and is redirected by a beam splitter to a detector. A lock-in amplifier converts the output of the detector to produce quadrature (Q) and in-phase (I) signals for analysis. A processor uses the Q and/or I signals to analyze the sample.