Custom Magnesium Fluoride (MgF₂) Windows

MgF₂ Windows

Magnesium Fluoride (MgF₂) Windows offer excellent broadband transmission from the deep-UV to the mid-infrared. DUV transmission makes them ideal for use at the UV radiation sources and receivers, as well as excimer laser applications. MgF₂ is a rugged material resistant to chemical etching, laser damage, and mechanical and thermal shock.

Description

Key Advantages

Broadest usable spectrum. Broadband 120 nm – 7 µm transmission; >90% transmittance across much of 0.4–5 µm.
Low refractive index. n≈1.38 minimizes Fresnel reflection and makes MgF₂ the classic low-index outer layer of broadband AR coatings.
Useful birefringence. Positive uniaxial crystal for UV waveplates and polarizers.
Rugged and durable. Knoop 415 kg/mm², stable in water and most environments, radiation-resistant.

Magnesium Fluoride (MgF₂) Windows Material Properties

Material	Magnesium Fluoride (MgF₂)
Transmission Range	0.12 – 7.0 μm
Refractive Index	No ≈ 1.376, Ne ≈ 1.388 @ 0.7 µm
Density	3.18 g/cm³
Coefficient of Thermal Expansion (CTE)	13.7 × 10⁻⁶/°C
Thermal Conductivity	21 W/(m·K)
Knoop Hardness	415 kg/mm²
Absorption Coefficient(1/cm)	40 × 10⁻³ cm⁻¹ @ 2.7 μm
Young's Modulus (GPa)	138 GPa
Poisson's Ratio	0.27
Melting Point	1255 °C

Processing Specifications

Parameters	Regular	High precision
Dimension	Φ5mm – Φ350mm
Diameter Tolerance	±0.2mm	±0.02mm
Thickness Tolerance	±0.2mm	±0.02mm
Parallelism (arcmin)	< 3′ (3 arcmin)	< 3″ (3 arcsec)
Surface Quality	60-40	40-20
Surface Flatness (P-V)	PV<2λ@632.8nm	PV<λ/10@632.8nm
Protective Bevel	0.1-0.3 mm × 45°；0.2-0.5 mm × 45°
Coating	AR, BBAR, HR coating