29 May 2001 Measurement of the second-order nonlinear susceptibility of collagen using polarization modulation and phase-sensitive detection
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Proceedings Volume 4276, Commercial and Biomedical Applications of Ultrashort Pulse Lasers; Laser Plasma Generation and Diagnostics; (2001); doi: 10.1117/12.428013
Event: Photonics West 2001 - LASE, 2001, San Jose, CA, United States
Abstract
The measurement of the second order nonlinear susceptibility of collagen in various biological tissues has potential applications in the detection of structural changes which are related to different pathological conditions. We investigate second harmonic generation in a rat-tail tendon, a highly organized collagen structure consisting of parallel fibers. Using an electro-optic modulator and a quarter-wave plate, we modulate the linear polarization of an ultra-short pulse laser beam that is used to measure second harmonic generation in a confocal microscopy setup. Phase-sensitive detection of the generated signal, coupled with a simple model of the collagen protein structures, allows us to measure a parameter (gamma) related to nonlinear susceptibility and to determine the relative orientation of the structures. Our preliminary results indicate that it may be possible to use this parameter to characterize the structure.
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Patrick Christian Stoller, Beop-Min Kim, Alexander M. Rubenchik, Karen M. Reiser, Luiz Barroca Da Silva, "Measurement of the second-order nonlinear susceptibility of collagen using polarization modulation and phase-sensitive detection", Proc. SPIE 4276, Commercial and Biomedical Applications of Ultrashort Pulse Lasers; Laser Plasma Generation and Diagnostics, (29 May 2001); doi: 10.1117/12.428013; https://doi.org/10.1117/12.428013
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KEYWORDS
Collagen

Modulation

Polarization

Signal detection

Tissues

Second-harmonic generation

Phase shift keying

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