Case Study: Dichroic Filter for separating PbS and PbSe System

Case Study: Beamsplitter for Lead Sulphide and Lead Selenide System Separation

Customer Challenge: The customers system had a SWIR section (1.3-2.3 µm) using a Lead Sulphide detector and a MID IR (3-5 µm) section using a Lead Selenide detector. There is a range at which both detectors are sensitive, and a dichroic filter was needed to ensure the light was directed into the relevant channel of the instrument. A sketch of the customers intention is shown in the diagram.

Vortex’s Solution: We designed a long wave pass dichroic filter to operate at angle of incidence of 45 deg. The customer did have some ‘budget considerations’ so to make the solution as inexpensive as possible, the lower wavelengths are reflected (1.3-2.3 µm) and the higher wavelengths are transmitted (3-5 µm). This is generally a good tip to keep the cost of dichroic filters down as long pass filters tend to have a shorter coating duration than short pass filters.

The Result: The filter was deposited using our magnetron sputtering process and the spectral results are shown in the spectral graph above. This filter could also be slightly modified to be a standard dichroic for the separating the MID IR and SWIR ranges.