Compressed sensing time-domain Brillouin scattering system acoustic velocity profiler for lithium niobate thin film wafers

Lithium niobate (LiNbO3) thin-film heterostructures, a critical platform for 5G acoustic filters and quantum devices, face challenges in wafer-scale acoustic uniformity control. To evaluate the spatial heterogeneity of acoustic velocity in LiNbO3/SiO2/Si multilayer heterostructures prior to device fabrication, this study developed a Compressed Sensing Time-Domain Brillouin Scattering (CS-TDBS) system. A thin-film-optimized stochastic sampling algorithm overcomes conventional TDBS efficiency constraints, enabling 20× faster measurements while maintaining signal correlation (>0.92) and spectral fidelity (>0.96). By mapping the acoustic velocity distribution on 4-in. LiNbO3 wafers, CS-TDBS has, for the first time, achieved the mapping of wafer-level acoustic velocity distribution in the open-circuit state in a non-destructive testing manner. It can accurately identify abnormal decreases in acoustic velocity in the 5 mm edge region of the wafer. The demonstrated capability for fast, non-destructive assessment of elastic properties positions CS-TDBS as a valuable solution for monitoring thin-film deposition processes in advanced heterostructure fabrication.