Chemical diffusion treated volume holograms and methods for making the same
A method for making an optical grating having a non-uniform refractive index profile along a direction substantially perpendicular to a plane defined by the optical grating includes placing a layer of photopolymerization material having a first surface and a second surface that is opposite to the first surface between a first material transfer layer and a second material transfer layer so that the first surface of the layer of photopolymerization material is in contact with the first material transfer layer and the second surface of the layer of photopolymerization material is in contact with the second material transfer layer to allow material transfer between the layer of photopolymerization material and the first and second material transfer layers by diffusion.
1. A method, comprising:
making an optical grating having a non-uniform refractive index profile along a direction substantially perpendicular to a plane defined by the optical grating, including placing a layer of photopolymerization material having a first surface and a second surface that is opposite to the first surface between a first material transfer layer and a second material transfer layer so that the first surface of the layer of photopolymerization material is in contact with the first material transfer layer and the second surface of the layer of photopolymerization material is in contact with the second material transfer layer to allow material transfer between the layer of photopolymerization material and the first and second material transfer layers by diffusion;
removing the first material transfer layer and the second material transfer layer from the layer of photopolymerization material; and
exposing the layer of photopolymerization material to two beams after removing the first material transfer layer and the second material transfer layer from the layer of photopolymerization material.
2. The method of claim 1 , further comprising:
exposing the layer of photopolymerization material to two beams that overlap with each other over at least a portion of the layer of photopolymerization material to form a volume hologram.
3. The method of claim 1 , further comprising:
polymerizing the layer of photopolymerization material.
4. The method of claim 1 , wherein:
the first material transfer layer and the second material transfer layer include polymerization inhibitors so that the polymerization inhibitors are transferred into the layer of photopolymerization material by diffusion; and
the layer of photopolymerization material is placed between the first material transfer layer and the second material transfer layer before exposing the layer of photopolymerization material to two beams that overlap with each other over at least a portion of the layer of photopolymerization material to form a volume hologram.
5. The method of claim 4 , wherein:
the polymerization inhibitors include one or more of: phenols, nitroxides, benzoquinones, or nitrosos.
6. The method of claim 4 , further comprising:
polymerizing the layer of photopolymerization material after exposing the layer of photopolymerization material to the two beams.
7. The method of claim 1 , wherein:
the first material transfer layer and the second material transfer layer include absorptive material so that one or more components of the layer of photopolymerization material are transferred to the first material transfer layer and the second material transfer layer by diffusion.
8. The method of claim 7 , further comprising:
exposing the layer of photopolymerization material to two beams that overlap with each other over at least a portion of the layer of photopolymerization material to form a volume hologram.
9. The method of claim 8 , wherein:
the layer of photopolymerization material is placed between the first material transfer layer and the second material transfer layer before exposing the layer of photopolymerization material to the two beams.
10. The method of claim 8 , wherein:
the layer of photopolymerization material is placed between the first material transfer layer and the second material transfer layer after exposing the layer of photopolymerization material to the two beams.
11. The method of claim 8 , further comprising:
exposing the first surface and the second surface of the layer of photopolymerization material to light before exposing the layer of photopolymerization material to the two beams.
12. The method of claim 8 , further comprising:
polymerizing the layer of photopolymerization material after exposing the layer of photopolymerization material to the two beams.
13. The method of claim 8 , wherein the absorptive material includes one or more of:
polyurethanes, polysiloxanes, thiol-enes, thiol-ynes, or ring opening metathesis polymers (ROMP).
14. The method of claim 1 , wherein:
the first material transfer layer and the second material transfer layer include a compound having a refractive index that is distinct from a refractive index of the layer of photopolymerization material so that the compound having a predefined refractive index is transferred to the layer of photopolymerization material by diffusion.
15. The method of claim 14 , wherein:
the refractive index of the compound is higher than the refractive index of the layer of photopolymerization material.
16. The method of claim 15 , wherein:
the compound includes one or more selected from the group consisting of:
17. The method of claim 14 , wherein:
the refractive index of the compound is lower than the refractive index of the layer of photopolymerization material.
18. The method of claim 17 , wherein:
the compound includes one or more selected from the group consisting of: