Symmetric and antisymmetric Lamb modes are excited in low‐frequency‐thickness regime by illuminating a thin plate with an array of Q‐switched Nd:YAG laser‐generated line sources. The propagation of laser‐generated Lamb waves is detected by measuring the out‐of‐plane displacements in a non‐contact manner using the fiber optic Sagnac interferometer. The laser generation and non‐contact detection of narrowband Lamb waves at the selected operating points with relatively small rate of change in group velocity is presented. © 2003 American Institute of Physics