Multi-timescale infrared quantum cascade laser ellipsometry

We recently introduced a novel, to the best of our knowledge, infrared laser ellipsometer for sub-decisecond spectroscopy [Opt. Lett.44, 4387 (2019)10.1364/OL.44.004387] and 0.03 mm spot-sized hyperspectral imaging [Opt. Lett.44, 4893 (2019)10.1364/OL.44.004893]. Here we report on the next device ge...

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Bibliographic Details
Published in:Optics letters 2022-06, Vol.47 (11), p.2834-2837
Main Authors: Furchner, Andreas, Kratz, Christoph, Rappich, Jörg, Hinrichs, Karsten
Format: Article
Language:English
Subjects:
Ellipsometry
Fatty acids
Hyperspectral imaging
Infrared lasers
Microfluidics
Molecular interactions
Molecular structure
Optical thickness
Phase transitions
Quantum cascade lasers
Solid phases
Spectral resolution
Surface reactions
Thin films
Time
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Summary:We recently introduced a novel, to the best of our knowledge, infrared laser ellipsometer for sub-decisecond spectroscopy [Opt. Lett.44, 4387 (2019)10.1364/OL.44.004387] and 0.03 mm spot-sized hyperspectral imaging [Opt. Lett.44, 4893 (2019)10.1364/OL.44.004893]. Here we report on the next device generation for thin-film sensitive simultaneous single-shot amplitude and phase measurements. The multi-timescale ellipsometer achieves 10 µs time resolution and long-term stability over hours at high spectral resolution (0.2 cm ). We investigate the temporal stages (from minutes to milliseconds) of fatty acid thin-film formation upon solvent evaporation from acetone-diluted microliter droplets. Optical thickness variations, structure modifications, and molecular interactions are probed during the liquid-to-solid phase transition. Multi-timescale ellipsometry could greatly impact fields like in situ biosensing, microfluidics, and polymer analytics, but also operando applications in membrane research, catalysis, and studies of interface processes and surface reactions.
ISSN:0146-9592
1539-4794
DOI:10.1364/OL.457688