New Coatings for Efficient and Compact UV Laser Systems

Through functional coatings, the optics have a specific transmission and reflectivity. (Source: LZH)

Through functional coatings, the optics have a specific transmission and reflectivity. (Source: LZH)

The Laser Zentrum Hannover e.V. (LZH) was working together with three partners in the Eurostars project CELL-UV to develop a compact, energy-efficient laser system for precise measurements and for the medical market. Durable, power-stable optics with low absorption rates are a prerequisite for energy-efficient laser systems. The Coatings Group of the LZH has therefore chosen ion beam sputtering (IBS) for coat-ing the optical components. This coating process enables a high density of optical coating layers, which makes them especially stable and resistant to high laser output. In order to reduce the absorption and diffusion of the optics, two approaches were investigated: a combination of coating materials, and the use of an additional ion beam source.

Schematic of an ion beam sputtering system. The ion beam comes from the left side and hits the coating material on the plate, which is released and deposited on the substrates (optics). The complete coating process is moni-tored using the optical wideband monitor. (Source: LZH)

Schematic of an ion beam sputtering system. The ion beam comes from the left side and hits the coating material on the plate, which is released and deposited on the substrates (optics). The complete coating process is moni-tored using the optical wideband monitor. (Source: LZH)

In order to reduce the absorption and diffusion of the hafnium oxide used in the UV(355 nm) range, materials with lower losses in these areas should be added. The scientists used a mixture of hafnium oxide (HfO2) und aluminum oxide (Al2O3) for the optical coatings. Using this approach, the partners could increase the output power (60 mW) and efficiency in a laboratory setting.

Using an additional ion source during the IBS process increased the energy of the particle build-up and decreased the diffusion of the layers. Also, the additional source makes it possible to remove layers that have already been deposited in a controlled manner and without damaging the coating. If this process is used during certain phases of the coating process, it reduces the absorption of the coating layers. The scientists determined the layer thickness curve during the ongoing process using the optical wideband monitor (BBM) developed at the LZH. (Source: LZH)

Links: Eurostars project CELL-UV • Cutting Edge Coatings GmbH, Hannover, Germany • HC Photonics Corp., HsinChu City, Taiwan • Cobolt AB, Solna, Sweden

Speak Your Mind

*