Optical waveguide gratings

• US 6,553,165 B1
• Filed: 07/14/2000
• Issued: 04/22/2003
• Est. Priority Date: 07/14/2000
• Status: Expired due to Fees

• Current Assignee: Applied WDM Incorporated
• Original Assignee: Applied WDM Incorporated
• Inventors: Temkin, Henryk, Kazarinov, Rudolf Feodor
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Amari, Alessandro V.
• Application Number:
  US09/616,745
• Time in Patent Office: 1,012 Days
• Field of Search: 385/14, 385/24, 385/37, 385/42, 385/45, 385/46, 385/130, 385/131, 359/130
• US Class Current: 385/46
• CPC Class Codes: G02B 2006/12119 Bend
• CPC Class Codes: G02B 6/12011 characterised by the arrayed waveguides, e.g. comprising a filled groove in the array section

Abstract

An optical waveguide device comprising a free space region, suitably provided by a slab waveguide, having optical signal ports for coupling to input and output waveguide sections and an optical waveguide grating including an array of grating waveguides coupling the free space region to a reflector surface to provide a folded structure. Dielectric waveguide structures are preferred. The grating includes tapered optical waveguide sections laterally spaced and optically isolated from each other which extend from the free space region, with the grating waveguides continuing as extensions of the tapered waveguide sections. Each of the grating waveguides differs in length from a neighboring grating waveguide by a constant increment, preferably an optical path length increment. The grating waveguides also include intermediate curved portions having respective curvatures which increase progressively, preferably in an approximately parabolic manner, according to the sequential location of the grating waveguides from a reference grating waveguide in the array.

Claims

1. An optical waveguide grating, suitable for operation in an optical transmission device, comprising:

an array of laterally spaced grating waveguides each having an end extending from a free space region and another end terminating at a reflector surface;

neighboring ones of said grating waveguides differing in optical path length from each other by a constant optical path length increment;

each of said grating waveguides includes a single curved portion connected to said free space region by a straight portion, said curved portions having respective radii of curvature which decrease progressively from one grating waveguide to the next according to the sequential location of the grating waveguides commencing from a reference grating waveguide, and wherein each said grating waveguide includes another straight portion extending tangentially to the curved portion of that grating waveguide and terminates at said reflector surface.

2. An optical waveguide grating according to claim 1, wherein the radii of curvature of said curved portions of the grating waveguides decrease from one grating waveguide to the next towards each opposite lateral side of the array of grating waveguides from a reference grating waveguide at or near the center of said array.

3. An optical waveguide grating according to claim 1, wherein the radii of curvature of said curved portions of the grating waveguides decrease in an approximately parabolic manner from one grating waveguide to the next as the numerical sequential location of a said curved portion increases from an intermediate grating waveguide location to respective locations at opposite lateral sides of the grating waveguide array.

4. An optical waveguide grating according to claim 3, wherein the rate of sequential decrease in the radii of curvature of said curved portions is modified from said approximately parabolic function to produce apodization of optical signal reflection at said curved portions located near the lateral edges of the grating waveguide array.

5. An optical waveguide grating according to claim 4, wherein the ratio of the radius of curvature of said curved portions of grating waveguides at the central region and at opposite edges of the grating waveguide array is approximately 3:

1.

6. An optical waveguide grating according to claim 1, wherein the rate of progressive decrease in the radii of curvature of said curved portions is selected to result in preferential attenuation of optical signal reflection at said curved portions located near the edges of the grating waveguide array.

8. A waveguide grating according to claim 1, wherein the reflector surface is a cylindrical surface.

9. A waveguide grating according to claim 8, wherein the cylindrical surface has an infinite radius.

10. A waveguide grating according to claim 1, wherein the length difference between the longest and the shortest grating waveguides approximates the length of the shortest waveguide grating.

11. An optical waveguide grating according to claim 1, wherein said free space region and said grating waveguides are defined by high refractive index core material sandwiched between low refractive index cladding materials.

12. An optical waveguide according to claim 11, wherein the ratio of the difference in length between the longest and shortest grating waveguides to the length of the shortest grating waveguide exceeds one half.

7. An optical waveguide grating suitable for operation in an optical transmission device, comprising:

an array of laterally spaced grating waveguides each having an end extending from a free space region and another end terminating at a reflector surface;

neighboring ones of said grating waveguides differing in optical path length from each other by a constant optical path length increment;

each of said grating waveguides includes a single curved portion connected to said free space region by a straight portion, said curved portions having respective radii of curvature which decrease progressively from one grating waveguide to the next according to the sequential location of the grating waveguides commencing from a reference grating waveguide, wherein each said grating waveguide includes another straight portion extending tangentially to the curved portion of that grating waveguide and terminates at said reflector surface, and wherein the overall length of the optical waveguide grating array is less than the overall length of the free space region, both measured along the general direction of extent of said array of grating waveguides.

13. An optical waveguide grating, suitable for operation in an optical transmission device, comprising:

an array of laterally spaced grating waveguides, said array having opposite peripheral grating waveguides on either side of a center region of said array, neighboring ones of said grating waveguides differing in length from each other by a constant optical path length increment such that the ratio of the difference in length between the longest and shortest grating waveguides to the length of the shortest grating waveguide exceeds one half;

each grating waveguide including a curved portion having a radius of curvature differing from the radius of curvature of the curved portion of a neighboring waveguide, the radii of curvature progressively decreasing in an approximately parabolic manner as the numerical sequential location of a said curved portion increases from curved portions at the center region of the array to each of said peripheral grating waveguides,

each said curved portion located between straight grating waveguide portions.

14. An optical waveguide grating according to claim 13, wherein the rate of decrease in the radii of curvature of said curved portions is modified from said approximately parabolic function to produce apodization of optical signal reflection at said curved portions located near the peripheral waveguides of the grating waveguide array.

15. An optical waveguide grating according to claim 13, wherein one of the straight grating waveguide portions of each of the grating waveguides extends tangentially to the curved portion of that grating waveguide and terminates at a reflector surface.

16. A waveguide grating, suitable for operation in an optical transmission device, comprising an array of laterally spaced grating waveguides, wherein:

said grating waveguides are laterally spaced apart and each grating waveguide has one end extending from a free space region;

neighboring ones of said grating waveguides differing in optical path length from each other by a constant optical path length increment;

said grating waveguides each includes a single curved portion, said curved portions having respective radii of curvature which decrease progressively from grating waveguide to grating waveguide according to the sequential location of each grating waveguide commencing from a reference grating waveguide;

wherein the overall length of the optical waveguide grating array is less than the overall length of the free space region, both measured along the general direction of extent of said grating waveguides.

17. A waveguide grating according to claim 16, wherein said grating waveguides each has an end, opposite from said one end, terminating in a common cylindrical reflector surface.