When a beam splitter divides the incoming light, some of the energy is inevitably lost, leading to a decrease in signal strength. Understanding how beam splitters affect signal attenuation and polarization is essential for optimizing systems in telecommunications, imaging, and laser applications. In the. So my understanding is that the actual phase shift depends on the beam splitter type used. So essentially we use $pi/_2$ as a means to an end (in illustrations of theories). Beamsplitters are often classified according to their construction: cube or plate. The beam splitter splits and then recombines infrared radiation, while the detector picks up the resulting signal. It's sensitive to both intensity and frequency. Together, they decide just how accurately an instrument captures those unique infrared “fingerprints” from different substances.