Precise broad-band anti-refection coating fabricated by atomic layer deposition

By demarcating the ranges of transition regions on different underlayers in atomic layer deposition (ALD), their effects on broad-band anti-refection (BBAR) coating (400–680 nm) are evaluated. In ALD, comparatively larger transition region of TiO2 on bare BK7 glass severely limits the fabricated precision of BBAR coating with a thin first layer. Considering that the transition region on existent ALD material is much thinner than that on bare substrate, a thick Al2O3 film is inserted as a pre-deposited layer on the substrate to completely overlay the transition region on bare BK7.A good agreement between the designed and experimental curves is obtained, and its average reflectance is 0.535% (400–680 nm) in practice.