Objective Accurate mechanical properties of materials, including Young's modulus, Poisson's ratio, and longitudinal and shear wave speeds, are essential for material evaluation and testing. A major challenge arises when dealing with multimodal ultrasound Lamb waves, especially those that closely approach or intersect in the spectrum or dispersion curves. This complexity is often due to hardware limitations, such as the bandwidth of generation and detection. Furthermore, accurately distinguishing these modes in dispersion curves, by identifying spectral peaks through the wavenumber resolution offered by the twodimensional Fourier transform method, often presents difficulties. Traditionally, most studies have relied on contact wedge transducer. However, laser ultrasound introduces a nondestructive testing method that significantly simplifies spatiotemporal modulation and enables noncontact generation detection. This approach is particularly advantageous for applications that require rapid material scanning, as it overcomes the challenges associated with traditional methods, enhancing accuracy and efficiency in material property analysis.Methods To address challenges in material parameter inversion, a novel approach was employed, utilizing a moving continuouswave laser source to generate multimodal Lamb waves in thin plates. This method was first validated through a materialparameter inversion study. Experimental findings, illustrated in Figs. 4 and 5, confirmed the effective generation of specific Lamb waves with distinct phase velocities. Importantly, this noncontact phasevelocity matching method overcame the limitations typically encountered with transducer use in contact scanning, enhancing the accuracy of dispersion curve measurements within the targeted range. Further investigations focused on parameter sensitivities in the fitting process, specifically for aluminum plates within a phase velocity range of 2500 -4000 m/s and a frequencythickness product range of 1 -20 MHz•mm. Additionally, as shown in Figs. 2 and 3, simulations and analyses were conducted to assess multimodal fitting under various noise levels. Building on these comprehensive insights, material parameters for aluminum and polystyrene plates of varying thicknesses were successfully obtained through the application of the particle swarm optimization algorithm, coupled with inertial descent.Results and Discussions Singlemodal data (specifically, the s1 modal, represented by the blue data points in Fig. 5(d)) are utilized for fitting when inverting the material properties of the polystyrene plate. When comparing the final fitting results with parameters found in the literature, the error for the longitudinal wave speed is only 0.26%, while that for the shear wave speed is 3.83%. A sensitivity analysis of this study reveals that the sensitivity of the longitudinal wave in the phase velocity range of 2500 -4000 m/s for the aluminum plates is relatively low. Errors in the measurement of the dispersion curve can lead to significant deviations in the in...