Optics: measuring and testing – For optical fiber or waveguide inspection
Patent
1991-01-15
1994-08-23
McGraw, Vincent P.
Optics: measuring and testing
For optical fiber or waveguide inspection
356357, 356358, G01B 902, G01N 2184
Patent
active
053412052
ABSTRACT:
An optical system and method include a short coherence length edge, emitt LED, a fiber optic coupler probe, and a Michelson interferometer to measure the parameter of thickness of optical devices, such as thin silicon substrate samples and to characterize other parameters of optical waveguide devices such as absolute attenuation, effective refractive index, and changes in these parameters with the application of a modulation voltage or an external disturbance. The measurable thickness range from a few to hundreds of microns with a thickness precision exceeding 0.1 micron for a 10 micron sample. In situ localized measurements of samples in an etching chamber are obtainable to control processing and provide for thickness uniformity. Attenuation measurements for optical waveguides compare the values of interferogram maxima at the values of the reference arm path length to changes corresponding to one and two times the optical path length of the sample. Effective refractive index is determined by counting the number of fringes in the recorded interferogram between successive maxima. Changes in these parameters due to an external disturbance are measured by comparing the interferograms before and after. The sample stays in the system during all measurements which can also indicate the degree of coupling or interaction between simultaneous refractive index and absorption changes.
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Albares Donald J.
McLandrich Matthew N.
Pappert Stephen A.
Fendelman Harvey
Keough Thomas G.
McGraw Vincent P.
The United States of America as represented by the Secretary of
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