Modern optical systems require still higher quality optical coatings.
Conventional production techniques are not able to give such high quality layers.
One of the main defaults comes from the relatively porous structure of the thin
films; as a consequence the sensitiveness of the materials to the moisture gives
noticeably unstable properties versus time. In this work, after a very short review of
the different techniques nowaday used to perform high quality optical thin films, we
will be especially interested in oxide layer production (Si02, Ta2O5, Ti02). To give a
good comparison of the performances obtained with techniques such as TAD and ion
plating we need extremely powerful characterization means:
- In vacuo measurements of optical properties allowing the study of
spontaneous water adsorption during air entrance;
- Absorption measurement with photothermal deflection spectroscopy;
- Scattering losses measurements and consequently determination of the
grain size of the microstructure.
Refractive index measurements, and optical anisotropy determined by
guided mode study.
Finally some views from electron microscopy justify the validity of the model
used with our characterization techniques. To end, we will show the interest of ion
plating technique when we are looking for very uniform deposition on large
Francois Flory, Francois Flory,
"Comparison of different technologies for high-quality optical coatings", Proc. SPIE 1270, Optical Thin Films and Applications, (1 August 1990); doi: 10.1117/12.20374; https://doi.org/10.1117/12.20374