Enhancement of SAW laser probe measurements by signal processing

Many different types of the SAW laser probe have been used for several years to characterize SAW devices as well as inherent properties of particular materials. Our laser probe is of a modified knife-edge type. Operating with a linear response, it has a high dynamic range. The probe provides full phasor information of the detected signal, and directional properties of the detection process makes it possible to determine the surface tilt components in two spatially orthogonal directions. We first sum up the basic characteristics of the probe. We show several examples where we take advantage of these features combined with signal processing techniques such as the fast Fourier transform. This enables us to concentrate on distinct properties of the devices under test. We thus exploit the spatial frequency domain and, in the basic detection process, the directions of the wavecrests, to enhance measurements of particular properties. Examples include results obtained from measurements on a selection of components containing various structures.