▼ Journal of Research (Science), Bahauddin Zakariya University, Multan, Pakistan. Vol. 17, No. 3, July 2006, pp. 145-153 ISSN 1021-1012 145 ▼J. res. Sci., 2006, 17(3), 145-153 THE OBSERVATION STUDY OF INFRARED LASER INDUCED PLASMA PLUME Rabia Qindeel, Noriah Bte Bidin and Yaacob B. Mat Daud Laser Technology Laboratory, Physics Department, Science Faculty, 81310 Universiti Teknologi Malaysia (UTM), Skudai, Johor. email: plasma_qindeel@yahoo.com Abstract The potential of laser-induced plasma is now becoming an important for fusion research in attempt to add the source of energy. Light energy can create plasma when high irradiance is focused. However, until today scientists and engineers still work hard to get the fusion energy into reality. Hence research is still going on to endeavor the knowledge and better understanding on laser plasma. In order to give some light on the problems, a fundamental study was carried to form the laser plasma. In this case, a high-power Q-switched Nd:YAG laser was employed to generate plasma. Camera lenses with various focal lengths were utilized to generate optical breakdown and initiate plasma plume on a cylindrical brass target. The plasma plume formation were visualized and recorded via CCD video camera. The recorded images were analyzed using Matrox Inspector version 2.1 and video test 5 softwares. The results obtained show that, the plasma area is linearly increased with focal length, which is in good agreement with the beam waist concept. Whereas, the length of plasma, related to the Rayleigh range was found quadratically change with focal length. Keywords: Focal length, high speed imaging, laser plasma plume, Q-Switched Nd:YAG laser. INTRODUCTION When a high-power laser beam is focused onto a solid surface, it can cause the removal of material by melting, vaporization, plasma plume formation, sublimation and a number of nonlinear processes [Atwee et al. 2001]. Pulsed laser induced plasma has a very short temporal existence and is transient in nature, with a fast evolution of the characteristic parameters that are heavily dependent on irradiation conditions such as incident laser intensity and irradiation spot size [Harilal Bindhu et al. 1997]. The characteristics of the plasma plume are dependent on laser irradiance, target composition and atmospheric condition [Harilal Bindhu et al. 1997, Liu et al. 1999]. The study of laser induced plasma plays a fundamental role for diagnostic purpose in many applications, concerning laser-matter interaction as pulsed laser deposition [Giardini et al. 2000, Teghil et al. 2001, Cappelli et al. 2002, De Giacomo et al. 2002, Teghil et al. 2002], laser induce breakdown [Ali and Bidin 2003], welding, cutting and so on. In spite of the fact that, in the last 10 years, a large number of experimental