Input light coupler using a pattern of dielectric contrast distributed in at least two dimensions

• US 6,574,383 B1
• Filed: 04/30/2001
• Issued: 06/03/2003
• Est. Priority Date: 04/30/2001
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Kolodziejski, Leslie A., Petrich, Gale S., Ripin, Daniel J., Erchak, Alexei A., Fan, Shanhui, Ippen, Erich P., Joannopoulos, John D.
• Primary Examiner(s): Healy, Brian
• Application Number:
  US09/845,811
• Time in Patent Office: 764 Days
• Field of Search: 385/15, 385/5, 385/27, 385/30, 385/38, 385/39, 385/24, 385/130, 385/131, 385/28, 385/122, 257/98, 257/94, 257/432, 372/101
• US Class Current: 385/15
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices

Abstract

An input light-coupling device comprising a dielectric layer containing a pattern of dielectric contrast distributed in at least two dimensions. The pattern of dielectric contrast, which may or may not be periodic, is designed to facilitate coupling to the dielectric layer of electromagnetic radiation. The electromagnetic radiation may be propagating within a surrounding medium of lower dielectric constant than that of said dielectric layer, input at directions including normal incidence from which light cannot typically couple to the dielectric layer without the presence of the pattern of dielectric contrast. The input light may constitute an optical signal propagating in an optical fiber or in free space. Light that is in-coupled may be directed in as many directions as dictated by the symmetry of the pattern of dielectric contrast. The dielectric layer may contain output waveguides surrounding the input coupling structure. The light coupling structure may be fabricated in a dielectric layer separated from a high-dielectric substrate by a low-dielectric layer to avoid losses of the input signal to the substrate. A mirror comprising either a reflective material or alternating layers of high and low dielectric material may be disposed between the low-dielectric layer and the substrate to enhance the total input coupling to the dielectric layer containing the input coupling structure.

Claims

1. An input light-coupling device comprising a dielectric structure with a dielectric layer including a pattern of dielectric contrast distributed in at least two dimensions, said pattern being arranged so as to optimally transfer at least one wavelength of electromagnetic radiation from a medium of smaller dielectric constant into said dielectric layer so that the transferred electromagnetic radiation is propagated within said dielectric layer in the in-plane direction of said dielectric layer.

2. The device of claim 1, wherein said dielectric layer comprises a pattern of dielectric contrast that is periodic in two dimensions.

3. The device of claim 2, wherein said dielectric layer comprises a periodic pattern of dielectric elements within a layer of different dielectric constant than that of said elements.

4. The device of claim 3, wherein said dielectric structure comprises a plurality of layers at least one of which contains said periodic pattern of dielectric elements.

5. The device of claim 3, wherein the periodicity of the dielectric layer terminates in the plane of said layer leaving a uniform dielectric material of said layer surrounding the periodic dielectric region, and bounded itself above and below by said medium of lower dielectric constant.

6. The device of claim 5 further comprising:

a substrate; and

a spacer layer with a dielectric constant below the dielectric constant of said substrate and positioned between said dielectric layer and the substrate.

7. The device of claim 6 further comprising a mirror between said substrate and said spacer layer.

8. The device of claim 7, wherein said mirror comprises alternating layers of dielectric material.

9. The device of claim 8, wherein said mirror comprises a reflective material.

10. The device of claim 6, wherein the periodic pattern extends through layers below said dielectric layer.

11. The device of claim 6, wherein said surrounding medium above said dielectric layer comprises an optical fiber.

12. The device of claim 6, wherein said surrounding medium above said periodic dielectric layer is free space.

13. The device of claim 6, wherein surrounding said dielectric structure are dielectric waveguides.

14. The device of claim 6, wherein surrounding said dielectric structure is a second periodic dielectric structure of a different periodicity than said periodic pattern.

15. The device of claim 14, wherein said second periodic dielectric structure comprises a photonic band gap or a range of frequencies in which light propagation is forbidden.

16. The device of claim 15, wherein the photonic band gap overlaps the wavelength of input light.

17. The device of claim 16, wherein within said second periodic dielectric structure are waveguides formed by constructing line defects that break the periodicity of said second periodic dielectric structure, the waveguides being defined along the directions of high-symmetry for said dielectric structure.

18. The device of claim 6 further comprising an optical cavity within said dielectric layer.

19. The device of claim 18, wherein output waveguides are positioned at the boundary of said optical cavity so that input light may couple through said dielectric structure exciting an optical mode inside said optical cavity, and light from said optical mode leaks into said output waveguides.

20. The device of claim 1, wherein said dielectric layer comprises an active medium and said dielectric structure facilitates optical pumping of said active medium.

21. The device of claim 20, wherein said active medium is also electrically pumped.

22. The device of claim 20, wherein said active medium comprises a light-emitting diode (LED).

23. The device of claim 20, wherein said active medium surrounds said periodic dielectric structure.

24. The device of claim 20, wherein light of at least one wavelength output from said active medium is input into a second dielectric layer through a second periodic dielectric structure positioned within said second dielectric layer.