Refractive indices of Gd₃Ga₅O₁₂ single crystals under shock compression to 100–290 GPa

Refractive indices of [111] Gd₃Ga₅O₁₂ single crystals under shock compression are investigated with planar impact and high-speed laser velocimetry, in the pressure range of 100–290 GPa. The refractive index, n, at 1550 nm is obtained as a function of shock pressure or density (ρ). n increases as pressure increases from 106 GPa to 201 GPa, and then drops sharply as a result of shock-induced melting; the $n−ρ$ relation is linear for the high pressure solid phase. We also establish the true particle velocity–apparent velocity relation for velocity correction.