Antireflection coating, optical element, and optical transceiver module

An antireflection coating provided on an optical element which passes through at least two wavelengths of light in the wavelength range of 1300-1600 nm. wherein the antireflection coating comprises:

• a high refractive index layer;
• a low refractive index layer having a refractive index lower than a refractive index of the high refractive index layer;
• and
• a supplementary layer having a composition different from a composition of the high refractive index layer or from a composition of the low refractive index layer, and being provided adjacent to the high refractive index layer or to the low refractive index layer, wherein
• the optical element comprises a first supplementary layer, a second supplementary layer and two high refractive index layers;
• the first supplementary layer is provided between the two high refractive index layers;
• the second supplementary layer is provided adjacent to the low refractive index layer;
• and
• the low refractive index layer and the supplementary layers each comprises a low refractive index material.