1,068 research outputs found
Band-Pass and OH-Suppression Filters for the E-ELT - Design and Prototyping
Optical filters are used for a variety of purposes at astronomical
telescopes. In the near infrared region, from 0.8 to 2.5 um, bandpass and edge
filters are used to separate the different astronomical channels, such as the
J, H, and K bands. However, in the same wavelength range light emission
generated in the earth's atmosphere is superimposed on the stellar radiation.
Therefore, ground based astronomical instruments measure, in addition to the
stellar light, also unwanted contributions from the earth's atmosphere. The
characteristic lines of this OH emission are extremely narrow and distributed
over the complete NIR spectral range. The sensitivity of future telescopes,
like the European Extreme Large Telescope (E-ELT) which is currently being
designed by ESO, can be dramatically improved if the atmospheric emission lines
are effectively suppressed while the stellar radiation is efficiently
transferred to the detector systems. For this task, new types of optical
filters have to be developed. In this framework new design concepts and
algorithms must be used, combining the measurement needs with practical
restrictions. Certainly, the selected deposition process plays the key role in
the manufacturing process. Precise and highly stable deposition systems are
necessary to realise such filter systems with an appropriate homogeneity.
Moreover, the production control techniques must be adapted to match the high
level of precision required in the NIR range. Finally, the characterisation
set-ups for such filters systems have to be provided. The manufacturing of such
a filter system for a feasibility study of an E-ELT instrument is presented.
The design development, the deposition with adapted Ion Beam Sputtering
deposition plants, and the characterisation of such filters in the J-Band is
described.Comment: contribution to SPIE 8168 on 'Advances in Optical Thin Films IV',
Marseille 201
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