Thorlabs offers flat windows fabricated from N-BK7, UV Fused Silica (UVFS), Sapphire, Calcium Fluoride, Magnesium Fluoride, Potassium Bromide, Infrasil, Zinc Selenide, Silicon, Germanium, or Barium Fluoride. To achieve a low average reflectance of <0.25% per surface over a broad wavelength range from 400 - 1100 nm, our UVFS textured windows feature a nanostructured surface. Our laser windows have a wavelength-specific AR coating centered around commonly used laser wavelengths and an optional wedge, while our precision windows are offered with or without a broadband AR coating. For more information on these substrates, please visit our Optical Substrates page.