Category:
Research Papers
Sub-Category:
Engineering (Applied)
Date Published:
April 28, 2026
Keywords:
evanescent light, DELI, optical nanoscopy, total internal reflection, optical waveguide, nanoprofile, thin films, z-profiling, DRLS
Abstract:
The Differential Evanescent Light Intensity (DELI) method is a wide-field, label-free, non-contact optical nanoscopy technique designed for axial profiling of nanometer-thin material layers deposited on optical waveguide substrates. The technique exploits the evanescent field generated by total internal reflection (TIR) at the waveguide/air interface, which illuminates deposited nanostructures and produces far-field scattered light signals detectable in a wide-field optical microscope. The evanescent field intensity scales with the local layer thickness, enabling nanometric depth profiling across areas up to several hundred square millimeters. The physical basis of DELI is based on a multi-stage theoretical framework that spans TIR decay theory, phenomenological photon extraction models, and full-field electromagnetic simulations grounded in Maxwell’s equations. Thickness reconstruction is performed pixel-wise through a discrete three-dimensional computational model, translating raw intensity maps into quantitative thickness distributions. Validation against atomic force microscopy (AFM), scanning electron microscopy (SEM), sputtering-rate calibration, and optical densitometry establishes a accuracy of 10–20% across diverse materials within a thickness range of 1–350 nm..../....
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