Microscopic fluorescence imaging of bulk defect clusters in KH₂PO₄ crystals

A microscopic fluorescence imaging system is used to detect optically active centers located inside a transparent dielectric crystal. Defect centers in the bulk of KH₂PO₄ crystals are imaged based on their near-infrared emission following photoexcitation. The spatial resolution of the system is 1 μm in the image plane and 25 μm in depth. The experimental results indicate the presence of a large number of optically active defect clusters in different KH₂PO₄ crystals, whereas the concentration of these clusters depends on the crystal sector and growth method.