Broadband Polarising Cube Beamsplitters
Thin
film stacks, deposited on the internal surface of a cube beamsplitter can
produce effective polarisers. The
coatings are designed to provide almost total reflection of the s-component and
a very high transmission of the p-component.
They operate over a broad spectral bandwidth.
A useful extinction ratio 500:1 can be obtained using high index SF2
glass. This extinction ratio covers a bandwidth of either 440-680
nm, 650-1000 nm, 900-1400 nm or 1200-1600 nm, centred on 550, 800, 1000 and 1400
nm respectively.
These
beamsplitters are usually supplied as 10 or 20 mm cubes but inch and other sizes
can be supplied on request.
A
lower cost form of polarising beamsplitter can be supplied for the visible
bandwidth using BK7 glass a substrate. This
version provides a lower, but still useful,
extinction ratio of about 200:1.