Planar waveguide reflective diffraction grating

• US 7,151,635 B2
• Filed: 10/25/2004
• Issued: 12/19/2006
• Est. Priority Date: 03/24/2004
• Status: Expired due to Fees

• Current Assignee: Enablence, Inc. (Enablence Technologies Incorporated)
• Original Assignee: Enablence, Inc. (Enablence Technologies Incorporated)
• Inventors: Balakrishnan, Ashok, Bidnyk, Serge, Pearson, Matt
• Primary Examiner(s): Assaf, Fayez G.
• Application Number:
  US10/971,129
• Publication Number:
  US 20050213214A1
• Time in Patent Office: 785 Days
• Field of Search: 359/572, 359/571, 359/569, 398/84, 385/37, 385/24, 385/129, 385/132
• US Class Current: 359/572
• CPC Class Codes: G02B 6/29326 Diffractive elements having focusing properties, e.g. curved gratings Rowland circle spectrometers G01J3/20
• CPC Class Codes: G02B 6/29328 Diffractive elements operating in reflection
• CPC Class Codes: G02B 6/2938 for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM

Abstract

The invention relates to a planar waveguide reflective diffraction grating for use in an optical device, such as a wavelength division multiplexer, providing an increased bandwidth over conventional planar waveguide reflection diffraction gratings while eliminating the polarization dependent loss (PDL) typically associated therewith. Accordingly, a low order (<3), high aspect ratio (>10) grating is provided with a very short side wall (less than the wavelength of the optical signal) for use with incident angles of less than 15°.

Claims

1. A reflective diffraction grating device on a planar waveguide platform for use in demultiplexing an optical signal, comprising:

an input port for launching a beam of light comprising a plurality of wavelength channels, defined by an average wavelength, at a small diffraction grating incident angle;

a reflective diffraction grating for dispersing the wavelength channels at various angles according to wavelength, the reflective diffraction grating having a plurality of substantially triangular steps, each step comprising a reflective wall defined by a facet length, and a sidewall defined by a sidewall length; and

a plurality of output ports positioned to capture the wavelength channels;

wherein an aspect ratio, defined by the facet length divided by the sidewall length, is greater than 3.

2. The device according to claim 1, wherein the aspect ratio is greater than 5.

3. The device according to claim 1, wherein the aspect ratio is greater than 10.

4. The device according to claim 3, wherein the diffraction grating incident angle is less than 6°

.

5. The device according to claim 3, wherein the sidewall length is less than or equal to two times the average wavelength.

6. The device according to claim 1, wherein the sidewall length is less than or equal to the average wavelength.

7. The device according to claim 1, wherein the incidence angle less than 30°

.

8. The device according to claim 1, wherein the incidence angle is less than 15°

.

9. The device according to claim 1, wherein the facet length is greater than 5 μ

m; and

wherein the sidewall length is less than 3000 nm.

10. The device according to claim 1, wherein the sidewall length is less than 1550 nm.

11. The device according to claim 1, wherein the incidence angle is less than 45°

.

12. A reflective diffraction grating device on a planar waveguide platform for use in multiplexing or demultiplexing optical channels defined by an average wavelength, comprising:

a reflective diffraction grating including a plurality of substantially triangular steps, each step comprising;

a reflective wall defined by a facet length; and

a non-reflecting sidewall defined by a sidewall length;

an input port for launching a beam of light comprising the optical channels at the diffraction grating at a small incident angle;

a first output port for outputting one of the optical channels; and

a second output port for outputting another of the optical channels;

wherein the facet length and the incident angle are selected to ensure that the grating provides diffraction in an order with an absolute value of 7 or less.

13. The device according to claim 12, wherein the order is 5 or less.

14. The device according to claim 12, wherein the order is 3 or less.

15. The device according to claim 14, wherein the diffraction grating incident angle is less than 6°

.

16. The device according to claim 15, wherein the sidewall length is less than or equal to the average wavelength.

17. The device according to claim 12, wherein the incidence angle is less than 45°

.

18. The device according to claim 12, wherein the incidence angle less than 30°

.

19. The device according to claim 12, wherein the incidence angle is less than 15°

.

20. The device according to claim 12, wherein the sidewall length is less than or equal to two times the average wavelength.

21. The device according to claim 12, wherein the sidewall length is less than or equal to the average wavelength.

22. The device according to claim 12, wherein the facet length is greater than 5 μ

m; and

wherein the sidewall length is less than 3000 nm.

23. The device according to claim 12, wherein the sidewall length is less than 1550 nm.

24. A reflective diffraction grating device on a planar waveguide platform for use in demultiplexing an optical signal, comprising:

an input port for launching a beam of light comprising a plurality of wavelength channels, defined by an average wavelength, at a small diffraction grating incident angle;

a reflective diffraction grating for dispersing the wavelength channels at various angles according to wavelength, the reflective diffraction grating having a plurality of steps defining substantially triangular grooves, each step comprising a reflective wall defined by a facet length, and a sidewall defined by a sidewall length; and

a plurality of output ports positioned to capture the wavelength channels;

wherein the sidewall length is less than or equal to twice the average wavelength.

25. The device according to claim 24, wherein the sidewall length is less than or equal to the average wavelength.

26. The device according to claim 24, wherein the sidewall length is less than 3000 nm.

27. The device according to claim 24, wherein the incidence angle is less than 1500 nm.

28. The device according to claim 24, wherein the incidence angle less than 45°

.

29. The device according to claim 24, wherein the incidence angle less than 30°

.

30. The device according to claim 24, wherein the incidence angle is less than 15°

.

31. A reflective diffraction grating device on a planar waveguide platform for use in demultiplexing an optical signal, comprising:

an input port for launching a beam of light comprising a plurality of wavelength channels, defined by an average wavelength, at a diffraction grating incident angle;

a reflective diffraction grating for dispersing the wavelength channels at various angles according to wavelength, the reflective diffraction grating having a plurality of steps defining substantially triangular grooves, each step comprising a reflective wall defined by a facet length, and a sidewall defined by a sidewall length; and

a plurality of output ports positioned to capture the wavelength channels;

wherein the sidewall length is less than or equal to twice the average wavelength; and

wherein the facet length is greater than 5 μ

m.

32. The device according to claim 31, wherein the sidewall length is less than 1550 nm.

33. The device according to claim 31, wherein the incidence angle is less than 45°

.