Ultrasound‐Induced Luminescence from Cr 3+ ‐Doped ZnGa 2 O 4 Glass–Ceramic Composites

An intense ultrasound‐induced luminescence (USL) from Cr 3+ ‐activated glass – ceramic composites, obtained by direct precipitation of nanoscale ZnGa 2 O 4 from silicate melts upon cooling, is reported. The USL band overlaps with the first near‐infrared transmission window of biological tissue and spans further into the visible red spectral range, generating interest for visible data encryption and labeling as well as for photophysical stimulation with a remote, non‐optical energy source. Time‐resolved observations of luminescence build‐up and decay, US heating, and persistent luminescence reveal thermal de‐trapping as the origin of the observed US sensitivity. The spectroscopic performance is very similar to that of phase‐pure ZnGa 2 O 4 , the fabrication process leads to a robust, dense, and biocompatible composite without requiring secondary encapsulation.