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Proceedings Paper

Interferometric mapping of material properties using thermal perturbation (Conference Presentation)

Paper Abstract

Optical phase changes induced by transient perturbations provide a sensitive measure of material properties. One such measure is associated with the change in refractive index with temperature. Another - with thermal expansion. We demonstrate the high sensitivity and speed of such methods using two interferometric techniques: Quantitative Phase Imaging (QPI) in transmission, and phase-resolved Optical Coherence Tomography (OCT) in reflection. Camera frame rate in QPI varied from 10 to 50 kHz, exposure from 1 to 10 µs, and heating pulse – from 0.02 to 1 ms in duration. The phase-stabilized swept-source OCT was operating at 100 kHz repetition rate. Shot-noise limited QPI can resolve energy deposition of about 3.4 mJ/cm^2 in a single pulse, which corresponds to 0.8 ℃ temperature rise in a single cell. OCT can detect deposition of 24 mJ/cm^2 energy between two scattering interfaces producing about 30 dB SNR signals and 4.7 mJ/cm^2 with 45 dB. Finite element modeling of the phase changes in materials heated by laser and by electric current matched the experimental results very well. These techniques can be used for mapping absorption coefficients, electric current density, doping depth in semiconductors, and many other properties. Integration of the phase changes along the penetrating beam path helps increase sensitivity and reveals the size of the hidden objects by looking at the signal relaxation time. These methods may enable multiple applications, ranging from temperature control in retinal laser therapy and in gene expression to characterization of semiconductor devices.

Paper Details

Date Published: 15 March 2018
Proc. SPIE 10503, Quantitative Phase Imaging IV, 1050309 (15 March 2018); doi: 10.1117/12.2293836
Show Author Affiliations
Tong Ling, Stanford Univ. (United States)
Georges Goetz, Stanford Univ. (United States)
Yijun Jiang, Stanford Univ. (United States)
Tushar Gupta, Stanford Univ. (United States)
Daniel Palanker, Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 10503:
Quantitative Phase Imaging IV
Gabriel Popescu; YongKeun Park, Editor(s)

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