Refractive index database

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Optical constants of BaGa4Se7 (Barium gallium selenide, BGSe)
Kato et al 2017: n(α) 0.901–10.6 µm

Wavelength: µm

Complex refractive index (n+ik)[ i ]

n   k   LogX   LogY   eV

Derived optical constants

Dispersion formula [ i ]



nα; room temperature.


K. Kato, K. Miyata, V. Petrov. Phase-matching properties of BaGa4Se7 for SHG and SFG in the 0.901–10.5910 μm range, Appl. Opt., 56, 2978–2981 (2017)


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BaGa4Se7 (BGSe)

BaGa4Se7, commonly abbreviated as BGSe, is a chalcogenide-based nonlinear optical crystal known for its phase-matching capabilities and broad transparency window. This material is particularly suited for frequency conversion applications in the mid-infrared region, including second-harmonic generation (SHG), sum-frequency generation (SFG), and optical parametric oscillation (OPO). BGSe exhibits high nonlinear optical coefficients, as well as a high laser damage threshold, making it well-suited for high-power applications. The crystal is generally grown using techniques like the Bridgman-Stockbarger method, and can be cut and polished into high-quality facets for optimal performance. One important consideration for this material is its sensitivity to moisture and other environmental factors; thus, careful handling and storage are required to maintain its optical properties. Overall, BGSe offers a compelling combination of properties that make it a valuable material for nonlinear optics, especially for applications requiring high efficiency and broad tunability in the mid-infrared range.

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