Non-contact single-mode guided wave technique by the combination of wavelength-matched laser generation and angle-matched leak wave detection

Abstract

This paper proposes a non-contact single-mode guided wave technique, where the laser beam illuminated through the arrayed line slits is used as the transmitter, and the air-couple transducer is used as the receiver. The line-arrayed laser illumination has a wavelength-matching effect that can generate only a few modes. The air-coupled transducer detects the leaky wave of the propagated guided wave, and by tuning the detection angle of the transducer we can detect the selected single mode. The proposed technique is fully non-contact and is possible to avoid difficulty in the mode identification. The experimental results for a 1-mm thick aluminum plate prove the usefulness of the proposed method, and most especially, it shows that the method is powerful in the generation and detection of anti-symmetric modes of the lowest order.