Main fields of work

A key area of the Characterization Group is the evaluation of optical transmission characteristics of functional surfaces. For this purpose, we design measurement stands that meet the relevant demands, or we adapt existing measurement stands according to ISO standards for experimental measurement  techniques and data evaluation methods. These fields of work are integrated in current research projects on optimizing optical components. Here, carrier materials (such as substrates, crystals etc.) and dielectric functional layers are of great importance. Apart from the research projects of the Characterization Group, the above described measurement stands can also be made available to companies, institutes or other research organisations.

In Germany, the Characterization Group offers the largest range of standard-compliant measurement techniques for optical laser components. A key are within the group is the characterization of materials in the vacuum ultraviolet (VUV) and extreme ultraviolet (EUV) spectral range. For these wavelength, LZH has designed and developed custom-built spectral photometers. In particular for the spectral range of EUV radiation, we are currently further developing the 8 to 20 nm system towards the high-energy range of the so called "water window" (2.3 to 4.4 nm). From the fundamental spectral characteristics of materials in this range one can draw conclusions about the surface contamination, chemical composition and even chemical bonding ratios.

Besides the evaluation of optical reflexion and transmission in particular spectral ranges, another key area is the characterization of optical losses. In the past, the measurement technique was optimized and commercialized for characterizing the absorption. Here, laser calorimetry is used to determine the absorption on a very high level with a detection sensitivity of ~ 0.1 ppm (ISO 11551). This includes typical excimer, fs-Ti:Saphir or Nd:YAG laser wavelengths. Moreover, using a laser source with variable frequency and medium output powers between 650 and 2200 nm, absorption bands can be spectrally resolved.

Another important field is the characterization of optics in terms of resistence and stability  when exposed to highly intensive laser radiation. The ISO 11254 measurement standard-compliant technique can be used for Nd:YAG laser radiation of up to 266 nm and for ArF-Excimer laser radiation up to 193 nm at high pulse energies. Moreover, adequate power compatibility measurement systems for the ultrashort pulse range are available, too. This measurement technique thus meets the increasing demands of industry and research. Characterizations of optics for space applications can also be carried out in the vacuum. Here, the phenomenon of premature ageing of optical functional layers in the vacuum is investigated as well.

Further measurement stands are available for environmental compatibility (ISO 

9211 3 and MIL 

C 48497) and the contamination of surfaces (ISO 10110 7). Here, we distinguish surfaces contaminated by organic or anorganic layers and surfaces contaminated by particles. At a dedicated measurement stand particle sizes and numbers optics can be mapped very quickly. This rapid measurement techique is also suitable for quality checks during industrial manufacturing processes.