A beam splitter reflects some of the infrared light and lets the rest pass through. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding widespread application in fibre optic telecommunications. Together, they decide just how accurately an instrument captures those unique infrared “fingerprints” from different substances. State-of-the-art implementations rely on elastic scattering processes from optical lattices such as Bloch oscillations or sequential Bragg. Beamsplitters separate incident light into two or more beams of the same wavelength.