Multi-level diffractive optical element thin film coating

1. A transmissive optical element, comprising:

a substrate;

a first anti-reflectance structure for a particular wavelength range formed on the substrate,

the first anti-reflectance structure including at least two layers of different refractive indexes;

a second anti-reflectance structure for the particular wavelength range formed on the first anti-reflectance structure,

the second anti-reflectance structure including at least two layers of different refractive indexes;

a third anti-reflectance structure for the particular wavelength range formed on the second anti-reflectance structure,

the third anti-reflectance structure including at least two layers of different refractive indexes; and

at least one layer disposed between the first anti-reflectance structure and the second anti-reflectance structure or between the second anti-reflectance structure and the third anti-reflectance structure,

wherein a first relief depth between a first surface of the first anti-reflectance structure and a second surface of the second anti-reflectance structure and a second relief depth between the first surface and a third surface of the third anti-reflectance structure are configured to form a diffractive optical element associated with a first phase delay and a second phase delay, respectively, for the particular wavelength range.

2. The transmissive optical element of claim 1 , wherein the first phase delay is a π/2 phase delay and the second phase delay is a π phase delay.

3. The transmissive optical element of claim 1 , wherein the first anti-reflectance structure, the second anti-reflectance structure, and the third anti-reflectance structure are formed from alternating layers of silicon and silicon dioxide.

4. The transmissive optical element of claim 1 , wherein the first anti-reflectance structure and the second anti-reflectance structure are formed from alternating layers of hydrogenated silicon and silicon dioxide.

5. The transmissive optical element of claim 1 , wherein the first anti-reflectance structure is formed from a first layer of a first material and a second layer of a second material,

the first layer and the second layer being included in the at least two layers of the first anti-reflectance structure;

wherein the at least one layer is formed from a third layer of the first material;

wherein the second anti-reflectance structure is formed from a fourth layer of the second material and a fifth layer of the first material,

the fourth layer and the fifth layer being included in the at least two layers of the second anti-reflectance structure; and

wherein the third anti-reflectance structure is formed from a sixth layer of the second material and a seventh layer of the first material,

the sixth layer and the seventh layer being included in the at least two layers of the third anti-reflectance structure.

6. The transmissive optical element of claim 1 , wherein the first anti-reflectance structure is formed on a first side of the substrate; and

the transmissive optical element further comprises:

a plurality of other anti-reflectance structures for the particular wavelength range formed on a second side of the substrate.

7. The transmissive optical element of claim 1 , wherein the first anti-reflectance structure, the second anti-reflectance structure, and the third anti-reflectance structure form a three-level relief profile.

8. The transmissive optical element of claim 1 , wherein the particular wavelength range is between 930 nanometers and 950 nanometers.

9. The transmissive optical element of claim 1 , wherein the particular wavelength range is between 1540 nanometers and 1560 nanometers.

10. An optical element, comprising:

a substrate;

a first anti-reflectance structure for a particular wavelength range formed on the substrate,

the first anti-reflectance structure including at least two layers of different refractive indexes, and

the at least two layers of the first anti-reflectance structure including a first etch stop layer with a first exposed surface of the optical element;

a second anti-reflectance structure for the particular wavelength range formed on the first anti-reflectance structure,

the second anti-reflectance structure including at least two layers of different refractive indexes, and

the at least two layers of the second anti-reflectance structure including a second etch stop layer with a second exposed surface of the optical element;

at least one other anti-reflectance structure for the particular wavelength range formed on the second anti-reflectance structure; and

wherein a relief depth between the first exposed surface and the second exposed surface is configured to form a diffractive optical element associated with a particular phase delay for the particular wavelength range.

11. The optical element of claim 10 , wherein the relief depth is between 0.4 micrometers and 3.0 micrometers.

12. The optical element of claim 10 , wherein the first anti-reflectance structure is an etch stop for etching the second anti-reflectance structure and the second anti-reflectance structure is an etch stop for etching the at least one other anti-reflectance structure.

13. The optical element of claim 10 , wherein the at least one other anti-reflectance structure includes a first other anti-reflectance structure and a second other anti-reflectance structure; and

wherein the first other anti-reflectance structure is an etch stop for etching the second other anti-reflectance structure.

14. The optical element of claim 10 , wherein at least one of the first anti-reflectance structure, the second anti-reflectance structure, or the at least one other anti-reflectance structure is formed using thin film deposition and etching.

15. The optical element of claim 10 , further comprising at least one layer disposed between the first anti-reflectance structure and the second anti-reflectance structure, between the second anti-reflectance structure and the at least one other anti-reflectance structure, or between two anti-reflectance structures of the at least one other anti-reflectance structure.

16. A method, comprising:

depositing a plurality of layers onto a wafer,

wherein the depositing forms three or more anti-reflectance structures for a particular wavelength range,

wherein the three or more anti-reflectance structures each include at least two layers of different refractive indexes,

wherein a first anti-reflectance structure, of the three or more anti-reflectance structures, is formed on the wafer and beneath a second anti-reflectance structure of the three or more anti-reflectance structures, and

wherein the second anti-reflectance structure is formed beneath a third anti-reflectance structure of the three or more anti-reflectance structures; and

etching a subset of layers of the plurality of layers to form a three or more-level relief profile,

wherein the etching forms a diffractive optical element associated with a particular phase delay for the particular wavelength range between the first anti-reflectance structure and another of the three or more anti-reflectance structures,

wherein the at least two layers of the first anti-reflectance structure include a first etch stop layer with a first exposed surface of the diffractive optical element, and

wherein the at least two layers of the second anti-reflectance structure include a second etch stop layer with a second exposed surface of the diffractive optical element.

17. The method of claim 16 , further comprising:

dividing the wafer into a plurality of diffractive optical elements.

18. The method of claim 16 , wherein the plurality of layers includes at least one of:

a silicon layer,

a silicon dioxide layer,

a tantalum pentoxide layer, or

a silicon nitride layer.

19. The method of claim 16 , wherein at least one layer is formed between two of the three or more anti-reflectance structures.

20. The method of claim 16 , further comprising:

forming another diffractive optical element including another three or more stacked anti-reflectance structures on another side of the wafer with the particular phase delay for the particular wavelength range.