We describe a spectrometer (visible‐ultraviolet photon energy range) for the measurement of reflectance‐difference spectra of cubic semiconductors. The spectrometer employs a photoelastic modulator to modulate the polarization of the light incident on the sample and allows for a simple procedure to correct the measured spectra for parasitic components associated with such modulation. The instrument reported has a higher throughput than more conventional setups. To illustrate the spectrometer performance we report on reflectance‐difference spectra of (001) oriented GaAs single crystals doped with silicon donors at a level of 1018/cm3.