Correction of optical distortions in dry depth profiling with confocal Raman microspectroscopy

Abstract

We present a generalized approach to obtain improved Raman intensity profiles from in-depth studies performed by confocal Raman microspectroscopy (CRM) with dry objectives. The approach is based on regularized deconvolution of the as-measured confocal profile, through a kernel that simulates optical distortions due to diffraction, refraction and collection efficiency on the depth response. No specific shape or restrictions for the recovered profile are imposed. The strategy was tested by probing, under different instrumental conditions, a series of model planar interfaces, generated by the contact of polymeric films of well-defined thickness with a substrate. Because of the aforementioned optical distortions, the as-measured confocal response of the films appeared highly distorted and featureless. The signal computed after deconvolution recovers all the films features, matching very closely with the response expected.