Smart Structures and Systems, Vol. 6, No. 5-6 (2010) 749-765 749 A wireless guided wave excitation technique based on laser and optoelectronics Hyun-Jun Park 1 , Hoon Sohn 1 * , Chung-Bang Yun 1 , Joseph Chung 2 and Il-Bum Kwon 3 Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Guseong-dong, Yuseong-gu, Daejeon, Korea Senior Manager, R&D Department, CyTroniq. Co. Ltd., Hoseo University, Sechul-ri, Baebang-myun, Asan, Korea Center for Safety Measurement, Korea Research Institute of Standards and Science, Doryong-dong, Yuseong-gu, Daejeon, Korea (Received November 18, 2009, Accepted February 11, 2010) Abstract. There are on-going efforts to utilize guided waves for structural damage detection. Active sensing devices such as lead zirconate titanate (PZT) have been widely used for guided wave generation and sensing. In addition, there has been increasing interest in adopting wireless sensing to structural health monitoring (SHM) applications. One of major challenges in wireless SHM is to secure power necessary to operate the wireless sensors. However, because active sensing devices demand relatively high electric power compared to conventional passive sensors such as accelerometers and strain gauges, existing battery technologies may not be suitable for long-term operation of the active sensing devices. To tackle this problem, a new wireless power transmission paradigm has been developed in this study. The proposed technique wirelessly transmits power necessary for PZT-based guided wave generation using laser and optoelectronic devices. First, a desired waveform is generated and the intensity of the laser source is modulated accordingly using an electro-optic modulator (EOM). Next, the modulated laser is wirelessly transmitted to a photodiode connected to a PZT. Then, the photodiode converts the transmitted light into an electric signal and excites the PZT to generate guided waves on the structure where the PZT is attached to. Finally, the corresponding response from the sensing PZT is measured. The feasibility of the proposed method for wireless guided wave generation has been experimentally demonstrated. Keywords: wireless power transmission; laser; optoelectronics; active sensing; guided wave generation. 1. Introduction In recent years, guided wave based structural health monitoring (SHM) techniques have attracted much attentions, because they are not only sensitive to small defects but also capable to propagate over a long distance in plate and pipe like structures. A number of studies have demonstrated the potential of guided wave based SHM (Moulin et al. 1997, Sohn 2003, Sohn et al. 2004, Kim and Sohn 2007, Raghavan and Cesnik 2007, Wang and Yuan 2007, Giurgiutiu 2008). Guided waves can be generated in a structure using various devices such as ultrasonic probes, piezoelectric elements and lasers. Ultrasonic probes include wedge-coupled (Guo and Cawley 1994), air-coupled (Castaings and Hosten 2001), fluid-coupled (Ghosh et al. 1998), and electro-magnetic *Corresponding Author, Associate Professor, E-mail: hoonsohn@kaist.ac.kr