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Proceedings Paper

Determination of optical constants of absorbing and nonabsorbing coatings: a computer-aided approach
Author(s): G. R. Mohan Rao; M. N. Annapurna; C. L. Nagendra; G. K. M. Thutupalli
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Paper Abstract

A dual stage, closed loop and self scanning algoritFin has been proposed for precise determination of optical constants i.e., refractive index, 'n', and absorption Index, 'k ' , together with thickness ' of thin film coatings . In the first stage , refractive index solutics over a knc.zn range are generated for a given set of nasured paranters , nanely,reflectance, R and trannittance , T, and preset thickness of the coating , where as in the seccd stage a merit function, defined in terms of mean square of the difference between refractive index values at consecutive wavelengths, is miriimised with respect to thickness. It is seen that while the algorithn can estimate the 'n ', ' and 'd ' to an accuracy better than 0.005, 0.002 and 5/50 A0 (5 A0 for visible region coatings and 50 A0 for infrared coatings ) for an experinntal error of +0 . 005 in R arid T and it is able to overccme the ambiguity of ns.iltiple solutions, inherent in the existing methods. Apart from this, the required data can be generated faster, dispensing the cunbersane and expensive graphic systems. The algoritFin has been successfully appiied to determine the optical constants of absorbing and transparent films.

Paper Details

Date Published: 1 October 1990
PDF: 12 pages
Proc. SPIE 1307, Electro-Optical Materials for Switches, Coatings, Sensor Optics, and Detectors, (1 October 1990); doi: 10.1117/12.21650
Show Author Affiliations
G. R. Mohan Rao, Andhra Univ. (India)
M. N. Annapurna, ISRO Satellite Ctr. (India)
C. L. Nagendra, ISRO Satellite Ctr. (India)
G. K. M. Thutupalli, ISRO Satellite Ctr. (India)


Published in SPIE Proceedings Vol. 1307:
Electro-Optical Materials for Switches, Coatings, Sensor Optics, and Detectors
Rudolf Hartmann; M. J. Soileau; Vijay K. Varadan, Editor(s)

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