Multi-layer thin film stack for diffractive optical elements

A method, comprising:

• depositing a plurality of layers onto a wafer,
• wherein the depositing forms a first anti-reflectance structure for a particular wavelength beneath a second anti-reflectance structure for the particular wavelength;
• and
• etching a subset of layers of the plurality of layers to form a two-level relief profile,
• wherein the etching forms a diffractive optical element associated with a particular phase delay for the particular wavelength between the first anti-reflectance structure and the second anti-reflectance structure.

A method, comprising:

• depositing a plurality of thin films onto a wafer using a thin film deposition technique,
• the depositing the plurality of thin films including depositing a first anti-reflectance structure for a particular wavelength, and depositing a second anti-reflectance structure for the particular wavelength after depositing the first anti-reflectance structure;
• depositing a mask onto a surface of the plurality of thin films;
• patterning the mask based on a set of determined transition points that define a plurality of regions of the wafer;
• etching a subset of thin films of the plurality of thin films to form a two-level relief profile based on the mask,
• wherein the etching forms a diffractive optical element associated with a π phase delay for the particular wavelength between the first anti-reflectance structure and the second anti-reflectance structure;
• and
• removing the mask.