High Frequency Optical Probe for BAW/SAW Devices

Optical probes are efficient tools to visualize surface displacements on top of SAW and BAW devices. The new generation of 5G RF Filters is expected to operate up to 6 GHz. The optical probes must therefore be able to detect surface vibrations up to at least this upper-limit frequency. In this paper we present characterization results obtained with an improved heterodyne interferometer, designed to detect high frequency surface vibrations up to 6 GHz. The tool was already successfully tested, on a reference SAW resonator driven at 900 MHz, a SAW transducer at 2.45 GHz, and a BAW resonator at 3.128 GHz.