Refractive index database

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Optical constants of BaGa4S7 (Barium gallium sulfide, BGS)
Badikov et al 2010: n(α) 0.420–9.50 µm

Wavelength: µm

Complex refractive index (n+ik)[ i ]

n   k   LogX   LogY   eV

Derived optical constants

Dispersion formula [ i ]



nα; room temperature.


V. Badikov, D. Badikov, G. Shevyrdyaeva, A. Tyazhev, G. Marchev, V. Panyutin, V. Petrov, A. Kwasniewski. Phase-matching properties of BaGa4S7 and BaGa4Se7: Wide-bandgap nonlinear crystals for the mid-infrared, Phys. Status Solidi RRL, 5, 31–33 (2010)


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BaGa4S7 (BGS)

BaGa4S7, often abbreviated as BGS in scientific literature and industry documents, is a nonlinear optical crystal known for its high phase-matching capabilities, especially in the visible and near-infrared regions. This material is particularly valuable for frequency conversion applications, such as second-harmonic generation (SHG) and sum-frequency generation (SFG), owing to its high nonlinear optical coefficients. BaGa4S7 is also known for its high laser damage threshold, making it a robust choice for high-power optical applications. Typically grown through methods like the Bridgman technique, the crystal can be precisely cut and polished to create high-quality optical elements. One consideration for users is the material's sensitivity to moisture and chemicals, which necessitates careful handling and storage to preserve its optical properties. Despite this, BaGa4S7 remains a highly attractive material for various nonlinear optical applications, especially those requiring wide tunability, high power-handling, and efficient phase-matching capabilities.

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