The substrate material of LBTEK ultrafast mirrors is fused silica, with a high-reflectance coating on the surface being a low group delay dispersion dielectric coating deposited using ion-beam sputtering (IBS). During the ion-beam sputtering process, a high-energy electric field accelerates the ion beam toward the target, causing ions to be sputtered from the target and releasing more ions, which ultimately deposit the coating on a rotating substrate. Using ion-beam sputtering enables high repeatability in batch coating and low coating layer thickness errors, thereby ensuring the corresponding design wavelength range and low group delay dispersion. Fused silica has a lower coefficient of thermal expansion and extremely high thermal shock stability, making it particularly suitable for high-power femtosecond pulsed lasers and imaging applications. Note: The direction indicated by the arrow engraved on the side edge corresponds to the coated surface. The wavelength range of LBTEK ultrafast mirrors is 340 nm–425 nm, 460 nm–590 nm, 700 nm–930 nm, 970 nm–1150 nm, and 1400 nm–1700 nm, with four options. The beam is incident at 45°, and the reflectance exceeds 99.5%.