Method to determine refractive index by use of optical focal shift

Author

Michael Burleson

Date of Award

2023

Document Type

Thesis

Degree Name

Master of Science in Engineering (MSE)

Department

Electrical and Computer Engineering

Committee Chair

Robert Lindquist

Committee Member

Laurie Joiner

Subject(s)

Refractive index, Optical measurements, Refractometers

Abstract

Documentation for optical polymer refractive indices tend to be listed for one wavelength, λ_d = 587.56 nm, out to only 2 decimal places. Optical glass catalogues generally list index values to 5 decimal places for 10-15 different wavelengths. This thesis describes a new approach to an old method to determine the indices of polymer samples at λ_HeNe = 632.8 nm (HeNe). It begins by introducing methods for measuring refractive index and their limitations. The property of Snell’s Law is then presented and it is shown how, with specific interferometer equipment, to determine the refractive index of a window. The method is analyzed to relate the material’s index, mechanical thickness, and focal shift according to the behavior of real rays. This behavior (spherical aberration) is analyzed and equations are derived to accommodate it. Experimental results are shown for calibration parts. Finally, a brief error analysis is presented.

Recommended Citation

Burleson, Michael, "Method to determine refractive index by use of optical focal shift" (2023). Theses. 622.
https://louis.uah.edu/uah-theses/622