US Patent 12019252 Optical element with diffractive focusing features and diffractive anti-reflection features

In an optical element, diffractive focusing features and diffractive anti-reflection features can extend into a first surface of a body, such as by etching. The diffractive focusing features can have a same first depth that is greater than a wavelength, and can be located in a first area to have a duty cycle that varies over the first area. The diffractive anti-reflection features can have a same second depth that is less than the wavelength. In some examples, an effective refractive index of the diffractive focusing features and the diffractive anti-reflection features, together, can be less than or equal to a specified value, such as 120% of a square root of a refractive index of a material of the body. In other examples, the diffractive anti-reflection features can be located in the first area to have a duty cycle that is constant over the first area.