Beam shaping using liquid crystal-on-silicon spatial light modulators for laser ultrasound generation

Michael K. Kalms; Sandra Hellmers; Philipp Huke; Ralf B. Bergmann

doi:10.1117/1.OE.53.4.044110

25 April 2014 Beam shaping using liquid crystal-on-silicon spatial light modulators for laser ultrasound generation

Michael K. Kalms, Sandra Hellmers, Philipp Huke, Ralf B. Bergmann

Author Affiliations +

Optical Engineering, Vol. 53, Issue 4, 044110 (April 2014). https://doi.org/10.1117/1.OE.53.4.044110

Abstract

The application of laser ultrasound for nondestructive testing of carbon fiber–reinforced plastics (CFRP) and carbon fiber–reinforced thermoplastics (CFRTP) is shown. Laser-generated excitation creates a three-dimensional, thermoelastic zone which emits ultrasound waves during expansion and contraction. In order not to exceed the damage threshold of the material to be tested usually only a low-energy density and therefore a weak excitation of ultrasound waves can be achieved. For instance, the use of a YAG laser type with a wavelength around 1 μm leads to a very low absorption in the matrix of CFRP while the absorption in the fibers is very high. As a consequence the excitation is often destructive. To solve this problem, we describe the successful introduction of a spatial light modulator to laser ultrasound allowing for tailored spatial energy distributions for efficient nondestructive excitation of ultrasound waves within CFRP or CFRTP.

Citation Download Citation

Michael K. Kalms, Sandra Hellmers, Philipp Huke, and Ralf B. Bergmann "Beam shaping using liquid crystal-on-silicon spatial light modulators for laser ultrasound generation," Optical Engineering 53(4), 044110 (25 April 2014). https://doi.org/10.1117/1.OE.53.4.044110

Published: 25 April 2014

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