Simultaneous holographic multiplexing methods are used to store multiple holograms concurrently into one holographic volume. Compared to serial exposure, one advantage is the higher processing speed. Additionally, for parallel exposure the different gratings develop in a linear relation to one another, although the developing process itself is nonlinear caused by the holographic photopolymer. A mechano-optical modulator using a rotating optical flat is introduced to enable economic single-shot exposure of centimeter to decimeter-sized holograms utilizing only one laser. The modulator specifically suppresses undesired interference, which occurs with this type of simultaneous exposure. A device concept of the modulator is presented. The application to simultaneous holographic multiplexing is theoretically discussed and experimentally demonstrated. The experimental results are compared to simulations and are evaluated. The functionality and practicability are proven, giving rise to a new design concept and a wider range of applications.