Thin-film plate polarizer with Fabry-Perot filter design

A thin-film plate polarizer with a polarization ratio T/Ts> 1000 for single laser wavelengths can be realized if a Fabry-Perot filter is used. The spectral width of the polarization region of the filter polarizer is smaller than that of the usual long-wave pass filter, but there are not the practical difficulties of depositing multilayer systems with a large number of layers having nonquarter-wave thicknesses. For theoretical analysis, the principle of equivalent layer is extended to the Fabry-Perot design. Experimental results of the Fabry-Perot filter polarizer for different laser wavelengths, and with different coating materials, are presented

Microstructured multilayer dielectric coatings with binary optical functions

Micropatterned interference filters have been developed by dry etching of dielectric multilayer stacks. Apart from the optical demands on the conventional filter design there are new requirements originating from the pattening process, which has to be stopped at the interface between two layers. In this paper the fundamental problems associated with the design and the development of micropatterned multilayer dielectric stacks are discussed. Details of the production of a two-stage filterarray are described and experimental results are presented

Micropatterned multilayer dielectric filters with two spectral characteristics

Micropatterned interference filters are developed by dry etching of dielectric multilayer stacks. The application of reactive-ion etching (RIE) techniques combined with the use of an etchstop layer are shown to be quite effective in producing two-stage micropatterns with defined spectral properties. By using a MgF2 underlayer the etching of TiO2 and Si02 layers is stopped exactly. Which provides the possibility to develop large area patterns (>lxl cm2) with feature sizes as small as 10 mu m. The distortion of edge features is shown to be better than 1 mu m. A filter array was developed providing high-reflection and antireflection coatings within a period of 20 mu m

Shift-free narrowband filters for the UV-B region

Monitoring of stratospherical ozone depletion by filter rediometers calls for narrowband filters with outstanding parameters. At filter wavelengths down to 300 nm narrow bandwidth, high peak transmittance together with high out-of-band blocking especially at longer wavelength are demanded. Furthermore, filters have to be completely free of wavelength shift caused by humidity. Conventional interference filters suffer from such shift because of the water sorption of the evaporated layers. By using plasma ion assisted deposition (Advanced Plasma Source - APS, Leybold) of zirconia and silicia layers we succeeded in manufacturing blocked two-cavity filters with full width at half maximum (FWHM) of 1.7 nm and peak transmittance of 17 per cent at the center wavelength in the UV-B region. Outside the transmission band from UV to NIR (>= 1000 nm) optical density is at least 6. There was no decrease in wavelength of such filters (without hermetisation) by changing relative humidity from 100 per cent to 0 per cent. Corresponding conventional filters shifted 4.5 nm under the same conditions. The filter performance achieved allows use for the development of sensitive and specific instrumentation for environmental, climate, and meterological research

Influence of substrate cleaning on LIDT of 355 nm HR coatings

An advanced high-purity reactive e-beam evaporation process was used to deposit Al2O3/SiO2 HR coatings for 355 nm (Nd: YAG third harmonic) high-power laser applications. Both 1:1 an R:1, 6 ns pulse width, laser-induced damage threshold (LIDT) tests for normal (0 deg) and non-normal (45 deg) incident designs were performed to study the influence of quartz substrate cleaning. Damage test results indicate very high LIDT values on clean substrates. Some tested points have R:1 LIDT above 20 J/cm2. Post-cleaning of coated substrates degrades LIDT

IAD of oxide coatings at low temperature: a comparison of processes based on different ion sources

A comparative study of different ion and plasma assisted physical vapor deposition processes at low temperature is reported. To work out a clear comparison of the different processes, the object of the study are single layers of different metal oxides like Ta2O5, TiO2, SiO2 and mixed oxides like H4 (Merck) deposited on glass and silicon substrates. Three different types of ion- (or plasma-respectively) sources are used: the cold cathode ion source from Denton (CC 104), the end hall ion source Mark II from CSC and the advanced plasma source from Leybold. Each of these processes is run under conditions concerning process parameters like bias, ion current, ion energy, beam characteristics and gas flow, which were understood to be optimized also to maintain long-term stability as realistic production conditions. The resulting metal oxide single layers are characterized by their optical properties, dispersion curves for NUV and VIS as well as absorption and scatter at discrete wavelengths. Also discussed are mechanical properties like hardness and adherence. A test method is presented which clearly shows the superior behavior of the IAD coatings