The conventional formula for the ellipsometric ratio ρ = rp/rs diverges in the limit when the dielectric constants on either side of an inhomogeneous layer become equal, ∊1 = ∊2. The general case, including ∊1 = ∊2, necessitates going to second order in the layer thickness. A formula is derived that includes the ∊1 = ∊2 case without divergence; the predicted maximum in the imaginary part of ρ when ∊1 ≈ ∊2 indicates that index matching (of the bounding media) can significantly increase the ellipsometric signal.
© 1988 Optical Society of America
Original Manuscript: October 21, 1987
Manuscript Accepted: January 26, 1988
Published: July 1, 1988
John Lekner, "Ellipsometry of a thin film between similar media," J. Opt. Soc. Am. A 5, 1041-1043 (1988)