Multi-wavelength optics for rangefinders

REO has introduced a new range of optics that offer high performance, multi-wavelength operation for military target designation and rangefinding applications. Specifically, these components deliver a unique combination of high reflectivity or transmission at multiple wavelength bands (e.g. 808nm, 1,064nm and 1,570nm) while also maintaining excellent wavefront quality (<λ/10 @ 633nm) in the reflected beam.

These optics can also accommodate high reflection or high transmission properties in the 3µm to 5µm spectral band, enabling common aperture FLIR applications. Just as important, they provide high laser damage threshold (typically >40 J/cm² for a 20ns pulse at 1,064nm) and exhibit exceptional environmental stability.

This performance benchmark is difficult to achieve, because multi-wavelength coatings of this type are often physically thick. This makes it challenging to keep film absorption and defects below acceptable limits, and to control layer stress which may lead to wavefront issues. However, REO utilises a range of fabrication and coating technologies, including advanced plasma source (APS) and ion beam sputtering (IBS) coating to enable the necessary level of control over coating structure, stoichiometry and stress.

These optics can be fabricated on a wide range of substrates, including fused silica, CaF2, ZnS, ZnSe, Si and sapphire, in sizes ranging from 0.5 to12-inches. Plano, spherical and aspheric surfaces can all be produced, as can non-circular and non-rectangular geometries, including substrates with through holes.