Beamsplitters

Beamsplitters separate incident light into two components consisting of a reflected and a transmitted band. Beamsplitters is designed so to achieve a specified reflectance and transmittance over a spectral range of interest. Beamsplitters are used also to separate two polarizations. Typically the splitter is situated in a 45°-angle to the incident beam Reflectance and transmittance of neutral beamsplitters are to be close to a constant in a specified spectral range. Values of reflectance and transmittance can be expressed in percentage, for example, 50% and 50%, 30% and 70% and so on.
	This beamsplitter operates in the spectral range from 400 to 800 nm. Target specifications: T=R=50% (unpolarized light) Materials: TiO2/SiO2, Glass substrate The details of the design process are shown in Beamsplitter at normal incidence
OptiLayer allows designing beamsplitters exhibiting any specified ratio T:R, for example, T=30% and R=70% (left pane) or T=70% and R=30% (right pane). Spectral range of interest can be, for example, from 450 to 650 nm and AOI equal to 45 degrees.

See the details of our design process in our video exercise at YouTube

immersed beamsplitter

The immersed 41-layer beamsplitter operates at AOI of 45 degrees in the spectral range from 400 to 500 nm.

Target specifications: Ts=Tp=50%

Materials: ZnS/Al2O3/MgF2, Glass substrate, Incident medium is Glass

Design method: Gradual evolution

Software tool: OptiLayer

Find illustration of the design process at YouTube

We can design an immersed polarizing beamsplitter operating in the spectral range from 400 to 700 nm for AOI of 65-75 degrees. Refractive index of the corresponding prism is 1.85.

These design specifications were taken from Li Li and J.A. Dobrowolski, “New developments in thin film polarizing beamsplitters”, in Optical Interference Coatings, Vol. 9, OSA Technical Digest Series, (Optical Society of America, Washington DC, 1998), pp. 158-160.

Target specifications:

Ts[%] > 99.9% for wavelengths 400-700 nm at AOI from 65 to 75 degrees
Tp[Optical Density] > 3.0 for wavelengths 400-700 nm at AOI from 65 to 75 degrees

Our video example at YouTube presents the details of the design procedure.