Abstract Micro-flowers of Cr3+ doped ZnGa2O4, a spinel compound with high chemical and thermal stability is synthesized by hydrothermal method. Flower-like structures in the micrometre range made up of secondary nanoflakes are evident from the field emission scanning electron microscope (FESEM) images. X-ray photoelectron spectroscopy (XPS) studies confirm the presence of Cr3+ dopants. The steady-state optical characterizations show higher absorbance of the samples in the ultraviolet (UV) region. Due to introduction of the d-d electron transition states of Cr3+ ions, ZnGa2O4:Cr3+ exhibits a prominent red near infrared (NIR) luminescence. Optical nonlinearity studies show that Cr3+ doping changes the nonlinear absorption from reverse saturable absorption (RSA) to saturable absorption (SA). This is due to the introduction of an excitation band owing to 4T1-4A2 transition of Cr3+ ion.
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