1 kHz 3.3 µm Nd:YAG KTiOAsO4 optical parametric oscillator system for laser ultrasound excitation of carbon-fiber-reinforced plastics.

We present a new laser prototype for laser ultrasonics excitation. The fundamental wavelength of a Q-switched Nd:YAG laser with a repetition rate of 1 kHz is converted to 3.3 µm with a KTiOAsO4 optical parametric oscillator. The achieved pulse energy at 3.3 µm is 1.7 mJ, and the pulse duration at the fundamental wavelength of 1.06 µm has been measured to be 21 ns. The ultrasonic excitation efficiency is about 3.5 times better compared to the application of state-of-the-art CO2 lasers.

Efficient laser generation of Lamb waves.

We report about the efficient generation of Lamb waves for nondestructive testing (NDT) of carbon fiber reinforced plastics (CFRP) with spatially formed laser beams. Therefore we describe the successful introduction of a liquid crystal on silicon (LCoS)-based spatial light modulator (SLM) to create predetermined spatial laser light distributions for a flexible Lamb wave excitation. We investigate the influence of the formed beam profiles of the generation laser to the resulting Lamb wave. The further objective of the study is the close adaptation of the laser-generated guided waves to a specific testing situation and an optimized defect evaluation.