## 4 Conclusions  
The results presented in this contribution clearly show the positive impact of the applied plasma treatment on the adhesiveness of UV-curing optical cement on polished glass surfaces. One has to notice that an improved stability up to a factor of about 4.6 as expressed by the adhesive pull strength was achieved after merely 10 s of plasma treatment. Such short-term process (for comparison, the polishing process takes approximately six hours) is thus of interest for precision cleaning of optics surfaces on an industrial scale. This approach could thus be integrated in existing production chains as an additional step prior to cementing after further preparatory work for technology transfer. For instance, the impact of scanning and rotation of the plasma source over the surface of larger optics surfaces on the homogeneity of plasma treatment and the resulting increase in adhesiveness should be investigated. Moreover, variations in thickness of an optical component lead to a change in discharge gap and plasma properties and composition, respectively. Such variations could be addressed and compensated by a dynamic adjustment of the output parameters of the used plasma power supply and the distance between the two involved electrodes.  
Moreover, plasma treatment does not only allow an enhanced cementation of optically active surfaces. It is also suitable as a preparation step for mounting processes of opto-mechanical systems. Here, optical elements are often fixed on mechanical holders or in lens mounts using two-component glues [5]. An improved wetting of such glues on polished glass surfaces was also observed in the course of comparative experiments in the present work. Here, a plasma-induced reduction in contact angle by a factor of approximately 1.6 (from 50.54\({}^{\circ}\) to 32.12\({}^{\circ}\)) was measured. It can thus finally be stated that--considering the advantage of a simple integration and the low gas temperature--dielectric barrier discharge plasmas at atmospheric pressure have a high potential in optics manufacturing and especially in surface cleaning and activation for improving the long-term stability of cemented and glued connections. Based on the findings of the present work it can moreover be assumed that the applied plasma treatment may also improve the stability and adhesiveness of dielectric and metallic coatings. This aspect will be investigated in ongoing work.  
[PERSON] acquired the funding and administrated the project, conceived and designed the experiments, analysed the data, visualised the obtained data, wrote the original draft, and reviewed and edited the final paper draft; [PERSON] prepared the samples, performed the experiments, analysed the data, and reviewed and edited the paper draft; [PERSON] supervised the experiments, validated the obtained results, and reviewed and edited the paper draft; [PERSON] acquired the funding and administrated the project, conceived experiments, and reviewed and edited the paper draft.  
This work was funded by the Federal Ministry for Economic Affairs and Energy (Bundesministerium fur Wirtschaft und Energie, BMWi) in the frame of the SME Central Innovation Programme (Zentrales Innovationsprogramm Mittelstand, ZIM), project \"Atmospheric pressure plasma finishing of optical components\" (\"Atmospharendruckplasma-Finishing optischer Komponenten\", AtmoKo), grant no. ZF 4047502 DF5.  
The authors thank [PERSON] and [PERSON] for their help during experimentation.  
The authors declare no conflict of interest. At the time of experimentation, the authors [PERSON] and [PERSON] worked at the IST Fraunhofer Institute for Surface Engineering and Thin Films, Application Center for Plasma and Photonic in Gottingen, Germany. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.