Grating structures and methods of making the grating structures

• US 20020135876A1
• Filed: 02/21/2001
• Published: 09/26/2002
• Est. Priority Date: 02/21/2001
• Status: Active Grant

• Current Assignee: Ibsen Photonics A/S
• Original Assignee: Ibsen Photonics A/S
• Inventors: Weichel, Steen, Holm, Johan Christer, Madsen, Henrik, Rose, Bjarke, Ibsen, Per Eld
• Granted Patent: US 6,762,880 B2
• Time in Patent Office: Days
• US Class Current: 359/566
• CPC Class Codes: G02B 5/1847 Manufacturing methods
• CPC Class Codes: G02B 5/1866 Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence

Abstract

New grating structures include a bonded transmission grating structure. The grating structure is encapsulated by two pieces that are bonded together. In addition, a new method of making grating structures includes forming wells with an aspect ratio (depth:width) of at least 3:1, 7:1 or greater. Such grating structures can be used to form gratings with high diffraction efficiencies for both TE and TM polarizations of light.

Claims

1. A transmission grating, comprising:

a first piece comprising a surface defining a grating structure; and

a second piece bonded to the surface of the first piece to encapsulate the grating structure.

2. The transmission grating of claim 1, wherein the second piece comprises a surface further defining the grating structure, wherein the surface of the first piece is bonded to the surface of the second piece to form the grating structure.

3. The transmission grating of claim 1, wherein the grating structure has an aspect ratio of at least 5:

1.

4. The transmission grating of claim 1, wherein the grating structure has an aspect ratio of at least 10:

1.

5. The transmission grating of claim 1, wherein the first and second pieces are formed of the same material.

6. The transmission grating of claim 1, wherein the grating structure has a depth such that first order grating efficiencies of the transmission grating for TE and TM polarized light are within 10% of each other.

7. The transmission grating of claim 1, wherein the grating structure has a depth such that first order grating efficiencies of the transmission grating for TE and TM polarized light are within 5% of each other.

8. The transmission grating of claim 1, wherein the second piece comprises a material that partially fills the grating structure.

9. A method of making a transmission grating, the method comprising:

forming a grating structure in a surface of a first piece; and

bonding a second piece to the surface of the first piece to encapsulate the grating structure.

10. The method of claim 9, further comprising treating at least one of the surface of the first piece and a bonding surface of the second piece to form reactive groups;

wherein bonding a second piece to the surface of the first piece comprises bonding the bonding surface of the second piece to the surface of the first piece using the reactive groups.

11. The method of claim 10, wherein the step of treating comprises plasma or acid treating at least one of the surface of the first piece and a bonding surface of the second piece to form the reactive groups.

12. The method of claim 10, further comprising annealing, after bonding, the first and second pieces.

13. The method of claim 12, wherein the step of annealing comprises heating the first and second pieces to at least 1000°

C.

15. The transmission grating of claim 14, further comprising a second-piece bonded to the surface of the first piece to encapsulate the grating structure.

16. The transmission grating of claim 14, wherein the wells have an average aspect ratio of at least 10:

1.

17. The transmission grating of claim 14, wherein individual diffraction efficiencies for TE and TM polarized light are at least 85% for at least one operational wavelength of the transmission grating.

18. The transmission grating of claim 14, wherein individual diffraction efficiencies for TE and TM polarized light are at least 95% for at least one operational wavelength of the transmission grating.

19. The transmission grating of claim 14, wherein individual diffraction efficiencies for TE and TM polarized light differ by no more than 5% for at least one operation wavelength of the transmission grating.

14. A transmission grating, comprising:

a first piece comprising a surface defining a grating structure, the grating structure comprising a plurality of wells, the wells having an average aspect ratio of at least 7;

1.

20. A transmission grating, comprising:

a first piece comprising a surface defining a grating structure, wherein individual diffraction efficiencies for TE and TM polarized light are at least 90% for at least one operational wavelength of the transmission grating.

21. The transmission grating of claim 20, further comprising a second piece bonded to the surface of the first piece to encapsulate the grating structure.

22. The transmission grating of claim 20, wherein the grating structure comprises a plurality of wells, the wells having an average aspect ratio of at least 7:

1.

24. The method of claim 23, wherein patterning a masking layer comprises forming a masking layer on the substrate;

forming a photoresist layer on the masking layer;

forming a pattern in the photoresist layer;

removing a portion of the photoresist layer according to the pattern; and

removing a portion of the masking layer according to the pattern.

25. The method of claim 24, wherein forming a pattern in the photoresist layer comprises exposing the photoresist layer to an interference pattern generated by at least two coherent light beams.

26. The method of claim 23, wherein etching the regions of the substrate comprises etching the regions of the substrate to form a plurality of wells in the substrate, the wells having an average depth:

width aspect ratio of at least 10;

1.

27. The method of claim 23, wherein etching the regions of the substrate comprises etching the regions of the substrate to form a plurality of wells in the substrate, the wells having an average depth:

width aspect ratio of at least 10;

1, wherein the average width of the wells at the surface of the substrate is no more than 600 nm.

28. The method of claim 23, wherein etching the regions of the substrate comprises etching the regions of the substrate using a deep reactive ion etching technique to form a plurality of wells in the substrate, the wells having an average depth:

width aspect ratio of at least 3;

1, wherein the average width of the wells at the surface of the substrate is no more than 1000 nm.

29. The method of claim 23, further comprising filling the plurality of wells with a dielectric material having an index of refraction that is different than an index of refraction of the substrate.

30. The method of claim 29, wherein filling the plurality of wells comprises filling the plurality of wells with a dielectric material, wherein a portion of the dielectric material is also disposed over the surface of the substrate.

31. The method of claim 30, further comprising planarizing the dielectric material to substantially expose the surface of the substrate between the plurality of wells.

32. The method of claim 23, further comprising disposing a dielectric material over the surface of the substrate and the plurality of wells to form a dielectric layer covering the plurality of wells.

33. The method of claim 32, wherein disposing a dielectric material comprises disposing the dielectric material over the surface of the substrate using a chemical vapor deposition technique that does not substantially fill the plurality of wells.

35. The method of claim 34, further comprising filling the plurality of wells with a dielectric material having an index of refraction that is different than an index of refraction of the waveguiding layer.

36. The method of claim 34, further comprising disposing a dielectric material over the surface of the waveguiding layer using a chemical vapor deposition technique that does not substantially fill the plurality of wells.

38. The method of claim 37, wherein observing an interference pattern comprises observing the interference pattern for at least two different points.

39. The method of claim 37, wherein observing an interference pattern comprises observing the interference pattern for at least three non-colinear points.

23. A method of making a grating structure, the method comprising:

patterning a masking layer disposed on a substrate to expose a plurality of regions of a surface of the substrate; and

etching the regions of the substrate to form a plurality of wells in the substrate, the wells having an average depth;

width aspect ratio of at least 3;

1, wherein the average width of the wells at the surface of the substrate is no more than 1000 nm.

34. A method of forming a grating structure, the method comprising:

forming a waveguiding layer on a substrate; and

removing a portion of the waveguiding layer to form a grating structure comprising a plurality of wells that are spaced apart with a substantially uniform period.

37. A method of forming a grating structure, the method comprising:

forming a first grating structure in a surface of a first piece of dielectric material;

forming a second grating structure in a surface of a second piece of dielectric material, the first and second grating structures having a substantially similar grating periods;

disposing the first piece over the second piece with the first and second grating structures adjacent;

observing an interference pattern between the first and second grating structures; and

moving at least one of the first and second grating structures based on the interference pattern to register the first and second grating structures.