Differential interferometry with suppression of the influence of refractive index of air for nanometrology

0385783 - ÚPT 2013 RIV CZ eng C - Conference Paper (international conference)
Holá, Miroslava - Číp, Ondřej - Hrabina, Jan - Buchta, Zdeněk - Lazar, Josef
Differential interferometry with suppression of the influence of refractive index of air for nanometrology.
NANOCON 2012, 4th International Conference Proceedings. Ostrava: TANGER Ltd, 2012, s. 805-810. ISBN 978-80-87294-32-1.
[NANOCON 2012. International Conference /4./. Brno (CZ), 23.10.2012-25.10.2012]
R&D Projects: GA ČR GA102/09/1276; GA ČR GPP102/11/P820; GA TA ČR TA02010711; GA TA ČR TE01020233; GA MŠMT ED0017/01/01
Institutional support: RVO:68081731
Keywords : refraktometry * nanopositioning * interferometry * nanometrology
Subject RIV: BH - Optics, Masers, Lasers

We present an interferometric technique based on differential interferometry setup for measurement in the subnanometer scale in atmospheric conditions. The motivation for development of this ultraprecise technique is coming from the field of nanometrology. The key limiting factor in any optical measurement are fluctuations of the refractive index of air representing a source of uncertainty on the 1*E-6 level when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of overdetermined interferometric setup where a reference length is derived from a mechanical frame made from a material with very low thermal coefficient on the 1*E-8 level. The technique allows to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range acting as a tracking refractometer. The principle is demonstrated on an experimental setup and a set of measurements describing the performance is presented.
Permanent Link: http://hdl.handle.net/11104/0215564