In this Photonics News issue we will look at somewhat more rare beam splitters.
Beam splitter cubes are used in power separation without beam displacement. The classic beam splitter cube is produced for a certain wavelength and direction of polarization. The heart of the cube is the hypotenuse, to which the appropriate dielectric coating is applied. The surfaces of beam entry and exit on the cube are AR coated, which means that four layers in total are applied to the cube. This explains the relatively high cost of cubes.
Polarizing beam splitter cubes. These components are always used when the laser power can be split via polarization. Cemented cubes are used for lasers with low energy and power densities; they are also available with broadband coatings. Optically-contacted versions are available for high-power applications: Damage thresholds above 10 J/cm² (10 ns, 10 Hz, 1064 nm) are quite resilient. In combination with l/2 retardation plates, polarization beam splitting cubes can even be used in power regulation.
Diffractive beam splitters are used for precise power separation in high-power lasers: in fact, it is even possible to separate the power into several identical beams (beam matrix). They are commonly used in laser material processing to make holes at precisely defined intervals, for example. With just one compact element, it is even possible to achieve two-dimensional beam matrices of 9 x 9 spots.
UV Coatings via IBS
Ion beam sputtering (IBS) technology is often used for challenging coatings in the Vis and NIR spectral range. It has not been possible to produce coatings for UV wavelengths using ion beam sputtering (IBS) technology because the absorption of coating material was too high.
A new material now makes that possible: For UV wavelengths starting at 260 nm, you may now rely on the many advantages offered by this high-tech coating: The very compact and homogeneous layers not only yield the highest damage thresholds but result in driftless and low-dispersion coatings.
