Furchner, A.; Kratz, C.; Rappich, J.; Hinrichs, K.: Multi-timescale infrared quantum cascade laser ellipsometry. Optics Letters 47 (2022), p. 2834–2837
10.1364/ol.457688
Open Access Version
Abstract:
We recently introduced a versatile infrared laser ellipsometer for sub-decisecond spectroscopy and 0.03 mm² spot-sized hyperspectral imaging. Here we report on the next device generation for thin-film sensitive simultaneous single-shot amplitude and phase measurements. The multitimescale ellipsometer achieves 10 μs time resolution and long-term stability over hours at high spectral resolution (0.2 cm−1). 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.