In 2011, we introduced variable beam splitters for the first time in which the degree of transmission changes across the position of the square beam splitter. A conversation with Uwe Schallenberg (US):
What are variable beam splitters used for?
US: One customer wanted to incorporate two beams in an assembly with a single laser; following the last optic in the system, the laser power of both partial beams were supposed to be identical. This would have been impossible with conventional beam splitters because the different components transmit light unevenly. It was necessary to develop the ability to variably adjust the beam splitting. We implemented this with an inhomogeneous layer distribution on a square substrate.
And now you have introduced a new design. What led to this development?
US: The reproducibility of the former design was particularly complex and costly. It was, therefore, our goal to develop a design that allows a more efficient production. Of course, it was necessary that the product specifications remain the same.
Were you successful?
US: Yes. Spectrally speaking, we no longer have any more lapses. The process is under control, and the reproducibility has increased significantly. We now manufacture these products using a machine with a lower capacity. Despite the lower quantities produced per batch, we were able to maintain, and in part even reduce the price because the cost and complexity of production were reduced – thanks to higher production accuracy.
Which product variations currently exist?
US: Very different ones because all of them are based on concrete customer requests: for example, for 1064 nm designs we have transmissions from 45% to 55% and 10% to 70% or for the wavelength 753 nm transmissions from 4% to 20%.
How have you verified the variable beam splitters?
US: At our facility, we perform comprehensive tests on the characterization of the inhomogeneity of the layer thickness. Based on these results, we produce mounts for different substrate sizes and optimize the reproducibility of the designs.
Are there any restrictions to implementing customer requests?
US: Generally speaking, we have two standard sizes: 45 mm x 22 mm and 70 mm x 22 mm. If a deviating size is required, it is necessary to develop new tools, which means a longer lead time.
Furthermore, the designs depend on the wavelength: If a variable beam splitter is developed for a wavelength of 532 nm, it does not function at another wavelength, for example at 515 nm.
The maximum length of the substrates is also restricted: at 70 mm. In larger substrates, changes to the layer thickness and thus changes to the reflection cannot be made.
