Barium Yttrium Fluoride (BaY₂F₈) crystallizes in the monoclinic Cm space group. It has good light transmittance in the range of 250~15000 nm; low phonon energy (360-380 cm^-1), lower refractive index and higher laser damage threshold, larger laser emission cross section, easy to dope with rare earth ions or transition metal ions. It is widely used as laser host when doped with rare earth ions.

Technical Data

Crystal Structure	monoclinic, a=0.69829 nm, b=1.05190 nm, c=0.42644 nm, α=γ=90°, β=99.676°
Density	4.97 g/cm³
Melting Point	998 ℃
Thermal Conductivity	6 W/(mK)
Thermal Expansion Coefficient	1.8×10^-5 /ºC
Hardness	4~5
Refractive Index	~1.5
Size	up to 30 mm
Thickness	up to 50 mm
Orientation	a-cut, b-cut, c-cut

Doping Ion	Tm³⁺	Ho³⁺	Tm³⁺, Ho³⁺	Yb³⁺	Pr³⁺
Absorption Peak Wavelength	791 nm	899 nm	791 nm	960 nm	445 nm
Absorption Cross Section	0.94×10^-20 cm²	1.29×10^-21 cm²	0.94×10^-20 cm²	9.8×10^-21 cm²	5.9×10^-20 cm²
Fluorescence Lifetime	17 ms	16.5 ms	10.1 ms	2.4 ms	43 μs (³P₀)
Laser Wavelength	1932 nm	2057 nm	2057 nm	1017 nm	495 nm, 524 nm, 553 nm
Emission Cross Section	0.25×10^-20 cm²	1.2×10^-20 cm²	1.2×10^-20 cm²	6.0×10^-21 cm²	2.6×10^-20 cm²(495 nm)

Reference

1. Tunability range of 245 nm in a diode-pumped Tm:BaY₂F₈ laser at 1.9 μm: a theoretical and experimental investigation, Applied Physics B, volume 85, 553–555 (2006)

2. Influence of Yb ions concentration on Ho: BaY₂F₈ crystals emission in the range of 1–3 μm, Optical Materials, Volume 109, November 2020, 110141