Fig. 1. Two-wave mixing device

Fig. 2. System configuration of multiple two-wave mixing (MTWM) interferometer

Fig. 3. Signals received by three adjacent elements in a nine-element array

Fig. 4. Experimental setup for qualitative analysis of dispersion curve using two-dimensional FFT technique

Fig. 5. Detected Lamb wave time traces with 0.98 mm spacing

Fig. 6. Recovered Lamb wave dispersion on an aluminum plate

Fig. 7. Dispersion curves of Lamb wave in aluminum plate obtained by experiment and theoretical calculation