What is the Principle of a Beam Splitter Prism?

A special semi-reflective coating is applied to the inclined surface inside the prism.

When light hits this coating, a fixed proportion of light is reflected, and the rest is transmitted—usually in a ratio such as 50:50, 70:30, or according to specific wavelength/polarization requirements.

The prism shape (often cube-type made of two right-angle prisms) ensures the reflected and transmitted beams exit at accurate right angles or other designed angles.

This avoids ghost images and distortion that can occur with flat plate beam splitters.

Energy splitting: Splits light by intensity (e.g., 50% reflection, 50% transmission).

Polarization splitting (PBS): Separates light into s-polarized and p-polarized components using polarization characteristics.

Spectral / dichroic splitting: Reflects one wavelength band and transmits another, based on thin-film interference.