Mode insensitive waveguide device

• US 5,212,759 A
• Filed: 12/16/1991
• Issued: 05/18/1993
• Est. Priority Date: 12/16/1991
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Kohnke, Glenn E., Brazas, John C. Jr.
• Primary Examiner(s): Healy, Brian
• Application Number:
  US07/808,705
• Time in Patent Office: 519 Days
• Field of Search: 385/28, 385/29, 385/129, 385/130, 385/131
• US Class Current: 385/130
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths

Abstract

A waveguide structure includes a substrate, a waveguide film, and an overlay material in contact with the waveguide film. The overlay material may also contact the substrate or the film may be disposed between the overlay and the substrate. The overlay material has a higher refractive index than the waveguide so that the ratio of the effective refractive indexes is substantially constant for all propagating modes supported by the waveguide.

Claims

1. An optical device, comprising:

a waveguide having a film, said film having a first film and a second film boundary spaced from said first film boundary, said waveguide internally reflecting an electromagnetic wave at said film boundaries, said wave being characterized by a projected wave vector, β

, on a z axis, where ##EQU3## and where λ

is the wavelength of light, n_w is the waveguide refractive index, and φ

_m represents the propagation angles supported by said waveguide for defined modes, m, so that an effective refractive index, N_wm, of said waveguide is a function of φ and

n_w where

space="preserve" listing-type="equation">N.sub.m =n.sub.w sin φ

.sub.m ; and

an overlay material positioned on said waveguide film and having a higher refractive index than said waveguide so that the ratio of the effective refractive indexes is substantially constant for all propagation angles, φ

_m, supported by said waveguide.

2. An optical device, as set forth in claim 1, including a substrate, said overlay material being formed on said substrate and disposed between said substrate and said film.

3. An optical device, comprising:

a waveguide having a substrate and a film formed on said substrate, said film having a first film boundary adjacent said substrate and a second film boundary spaced from said substrate, said waveguide internally reflecting an electromagnetic wave at said film boundaries, said wave being characterized by a projected wave vector, β

, on a z axis, where ##EQU4## and where λ

is the wavelength of light, n_w is the waveguide refractive index, and φ

_m represents the propagation angles supported by said waveguide for defined modes, m, so that an effective refractive index, N_wm, of said waveguide is a function of φ and

n_w where

space="preserve" listing-type="equation">N.sub.m =n.sub.w sin φ

.sub.m ; and

an overlay material positioned on said waveguide film and having a higher refractive index than said waveguide so that the ratio of the effective refractive indexes is substantially constant for all propagation angles, φ

_m, supported by said waveguide.

4. An optical device, as set forth in claim 3, wherein said waveguide has a thickness of 5 μ

m.

5. An optical device, as set forth in claim 3, wherein said waveguide supports six modes of propagation.

6. An optical device, as set forth in claim 3, wherein the overlay thickness for the least modal dispersion is 4.71 μ

m.

7. A waveguide structure, comprising:

a substrate having a refractive index, n_s ;

a waveguide film formed on said substrate and having a refractive index, n_w, with n_w being larger than n_s ;

an overlay material positioned on said waveguide film and having a refractive index, n_ol, with n_ol being larger than n_w ; and

8. A waveguide structure, as set forth in claim 7, wherein n_c is less than n_ol.

9. A waveguide structure, as set forth in claim 7, wherein n_c is less than n_w.

10. A waveguide structure, as set forth in claim 7, wherein n_s =1.453.

11. A waveguide structure, as set forth in claim 7, wherein n_w =1.544.

12. A waveguide structure, as set forth in claim 7, wherein n_ol =1.640.

13. A method for fabricating a waveguide structure having a substrate and a waveguide firm formed on the substrate, said substrate having a refractive index n_s, said waveguide film having a refractive index n_w, said method comprising:

selecting a substrate having a refractive index, n_s ;

forming a waveguide film having a refractive index, n_w, with n_w being larger than n_s ;

forming overlay material having a refractive index, n_ol, on the waveguide film with n_ol being larger than n_w ; and

forming a cladding having a refractive index n_c on said overlay.

14. A method, as set forth in claim 13, wherein n_c is less than n_ol.

15. A method, as set forth in claim 13, wherein n_c is less than n_w.

16. A waveguide structure, comprising:

a substrate having a refractive index, n_s ;

a waveguide film formed on said substrate having a refractive index, n_w, with n_w being larger than n_s ;

an overlay material positioned on said waveguide film and having a refractive index, n_ol, with n_ol being larger than n_w, and

n_w is substantially equal to the average of n_s and n_ol.

17. A waveguide structure, as set forth in claim 16, wherein n_s is 1.453, n_w is 1.482, and n_ol is 1.544.

18. A waveguide structure, as set forth in claim 16, wherein n_s is 1.453, n_w is 1.544, and n_ol is 1.650.

19. A method for fabricating a waveguide structure having a substrate and a waveguide film formed on the substrate, said method comprising:

selecting a substrate having a refractive index, n_s ;

forming a waveguide film having a refractive index, n_w, with n_w being larger than n_s ;

forming overlay material having a refractive index, n_ol, on the waveguide film with n_ol being larger than n_w and n_w being substantially equal to the average of n_s and n_ol.

20. A method for fabricating a waveguide structure having a substrate and a waveguide film formed on the substrate, said method comprising:

selecting a substrate having a refractive index, n_s ;

forming overlay material having a refractive index, n_ol, on the substrate with n_ol being larger than n_s ; and

forming a waveguide film having a refractive index, n_w, on the overlay material, with n_ol being larger than n_w and n_w being substantially equal to the average of n_s and n_ol.