Abstract
A new method, that involves Evanescent-Wave Cavity Ring-Down Spectroscopy (EW-CRDS), is presented. This method is
useful for the study of thin films on optical solid surfaces. The new design of experimental set-up incorporates a
semicylindrical prism with a plane surface where the Total Internal Reflection (TIR) effect appears. The antireflex (AR)
coated cylindrical surface of the prism induces the stability of resonant cavity. The evanescent wave generated at the plane
surface of the prism probes the absorption by matter in the vicinity of the prism. A general discussion of design criteria is
presented to quantify intrinsic losses, and then absorption spectra for Rhodamine chloride R590 from 555 to 560 nm are
presented to demonstrate the sensitivity of the system. The layer of R590 on BK7 surfaces is deposited from a solution of
R590 in ethanol (92% purity) with 51 mg/l concentration. After vaporization of the ethanol the dye layer on surfaces is
supposed to be uniform. This implementation of TIR surface in a resonant cavity provides a powerful new spectroscopic tool
especially to angle-resolved diagnostic for interfaces and thin-films. The loss spectrum can be obtained for an angular
range from the TIR critical angle to a maximum angle when the resonance of system is lost..
Keywords
Cavity Ring-Down Spectroscopy (CRDS), Evanescent Wave (EW), Total Internal Reflection (TIR), Thin film-solid interface.
Citation
C. COTIRLAN, C. LOGOFATU, A. RIZEA, M. F. LAZARESCU, Angle-resolved evanescent-wave cavity ring-down spectroscopy for thin film-solid interface characterization, Optoelectronics and Advanced Materials - Rapid Communications, 5, 7, July 2011, pp.709-714 (2011).
Submitted at: June 17, 2011
Accepted at: July 25, 2011