Polyloaded optical waveguide devices and methods for making same

• US 20030003736A1
• Filed: 05/15/2002
• Published: 01/02/2003
• Est. Priority Date: 05/17/2001
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Optronx Inc.
• Inventors: Delwala, Shrenik
• Granted Patent: US 6,891,985 B2
• Time in Patent Office: Days
• US Class Current: 438/689
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 2006/12038 Glass (SiO2 based materials)
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 2006/12097 Ridge, rib or the like
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 2006/12107 Grating
• CPC Class Codes: G02B 2006/12114 Prism
• CPC Class Codes: G02B 2006/12135 Temperature control
• CPC Class Codes: G02B 2006/12161 Distributed feedback [DFB]
• CPC Class Codes: G02B 2006/12164 Multiplexing; Demultiplexing
• CPC Class Codes: G02B 2006/12176 Etching
• CPC Class Codes: G02B 27/285 comprising arrays of elements, e.g. microprisms
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 6/10 of the optical waveguide type G02B6/02, G02B6/24 take precedence; devices or arrangements for the control of light by electric, magnetic, electro-magnetic or acoustic means G02F1/00; transferring the modulation of modulated light G02F2/00; optical logic elements G02F3/00; optical analogue/digital converters G02F7/00
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/12011 characterised by the arrayed waveguides, e.g. comprising a filled groove in the array section
• CPC Class Codes: G02B 6/12026 characterised by means for reducing the temperature dependence
• CPC Class Codes: G02B 6/12033 characterised by means for configuring the device, e.g. moveable element for wavelength tuning switching G02B6/35; thermo-optic devices G02F1/0147
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: G02B 6/1228 : Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/124 : Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/2861 : using fibre optic delay lines and optical elements associated with them, e.g. for use in signal processing, e.g. filtering delay lines in general H03H, H01P9/00; optical computing devices G06E
• CPC Class Codes: G02B 6/29349 : Michelson or Michelson/Gires-Tournois configuration, i.e. based on splitting and interferometrically combining relatively delayed signals at a single beamsplitter
• CPC Class Codes: G02B 6/29358 : Multiple beam interferometer external to a light guide, e.g. Fabry-Pérot, etalon, VIPA plate, OTDL plate, continuous interferometer, parallel plate resonator G02B6/29347, G02B6/29349, G02B6/2935, G02B6/29361 take precedence; resonator evanescently coupled to light guide G02B6/29335
• CPC Class Codes: G02B 6/34 : utilising prism or grating G02B6/293 takes precedence
• CPC Class Codes: G02B 6/4215 : the intermediate optical elements being wavelength selective optical elements, e.g. variable wavelength optical modules or wavelength lockers G02B6/4246 takes precedence
• CPC Class Codes: G02B 6/4232 : using the surface tension of fluid solder to align the elements, e.g. solder bump techniques flip-chip mounting techniques in assembly of semiconductor devices H01L24/81
• CPC Class Codes: G02B 6/43 : Arrangements comprising a plurality of opto-electronic elements and associated optical interconnections
• CPC Class Codes: G02F 1/0147 : based on thermo-optic effects G02F1/132 takes precedence
• CPC Class Codes: G02F 1/0152 : using free carrier effects, e.g. plasma effect
• CPC Class Codes: G02F 1/025 : in an optical waveguide structure G02F1/017, G02F1/2257 take precedence
• CPC Class Codes: G02F 1/295 : Analog deflection from or in an optical waveguide structure]
• CPC Class Codes: G02F 2201/20 : delay line
• CPC Class Codes: H01L 27/1203 : the substrate comprising an insulating body on a semiconductor body, e.g. SOI three-dimensional layout H01L27/0688

Abstract

A passive optical waveguide device deposited on a wafer that includes an insulator layer and an upper semiconductor layer formed at least in part from silicon. The upper silicon layer forms at least part of an optical waveguide, such as a slab waveguide. The passive optical waveguide device includes an optical waveguide, a gate oxide, and a polysilicon layer. The optical waveguide is formed within the upper semiconductor layer, a gate oxide layer that is deposited above the upper semiconductor layer, and a polysilicon layer that is deposited above the gate oxide layer. The polysilicon layer projects a region of static effective mode index within the optical waveguide. The region of static effective mode index has a different effective mode index than the optical waveguide outside of the region of static effective mode index. The region of static effective mode index has a depth extending within the optical waveguide. The value and position of the effective mode index within the region of static effective mode index remains substantially unchanged over time.

Claims

1. A passive optical waveguide device deposited on a Silicon-on-Insultor (SOI) wafer, the SOI wafer including an insulator layer and an upper semiconductor layer formed at least in part from silicon, the passive optical waveguide device comprising:

an optical waveguide formed within the upper semiconductor layer, a gate oxide layer deposited above the upper semiconductor layer, and a polysilicon layer formed at least in part from polysilicon and deposited above the gate oxide layer;

wherein the polysilicon layer projects a region of static effective mode index within the optical waveguide, the region of static effective mode index has a different effective mode index than the optical waveguide outside of the region of static effective mode index, the region of static effective mode index has a depth extending within the optical waveguide, and wherein a value and a position of the effective mode index within the region of static effective mode index remains substantially unchanged over time and applies a substantially unchanging optical function to light travelling through the region of static effective mode index over the lifetime of the passive optical waveguide device.

2. The passive optical waveguide device of claim 1, wherein the gate oxide layer is deposited adjacent to an etched portion of the upper semiconductor layer.

3. The passive optical waveguide device of claim 1, wherein the SOI wafer further includes a substrate, wherein the insulator layer is located between the upper semiconductor layer and the substrate.

4. The passive optical waveguide device of claim 3, wherein the substrate includes one or more materials from the group of silicon, diamond, glass, or sapphire.

5. The passive optical waveguide device of claim 1, wherein an optical function of the region of static effective mode index is a factor of the shape of the polysilicon layer.

6. The passive optical waveguide device of claim 1, wherein a shape of the region of static effective mode index closely mirrors the shape of the polysilicon layer.

7. The passive optical waveguide device of claim 1, wherein the polysilicon layer includes polySiGe.

8. The passive optical waveguide device of claim 1, wherein the thickness of the optical waveguide is less than or equal to 10 microns.

9. The passive optical waveguide device of claim 1, wherein the optical waveguide has a width, wherein the region of static effective mode index has a substantially uniform light propagation rate across the width of the optical waveguide.

10. The passive optical waveguide device of claim 1, wherein the polysilicon layer is substantially undoped.

11. The passive optical waveguide device of claim 1, wherein the polysilicon layer is doped.

12. The passive optical waveguide device of claim 1, wherein the polysilicon layer is shaped to cause the passive optical waveguide device to function as a lens.

13. The passive optical waveguide device of claim 1, wherein the polysilicon layer is shaped to cause the passive optical waveguide device to function as an Echelle grating.

14. The passive optical device of claim 1, wherein the upper semiconductor layer includes at least one etched portion and at least one unetched portion, and the optical waveguide including a total internal reflection (TIR) boundary between the unetched portion and the etched portion, wherein the TIR boundary constrains light that is flowing within the unetched portion from flowing through the TIR boundary into the etched portion.

15. The passive optical waveguide device of claim 14, wherein the TIR boundary constrains light flowing within the region of static effective mode index.

16. The passive optical waveguide device of claim 14, wherein the TIR boundary constrains light flowing outside of the region of static effective mode index.

18. The passive optical waveguide device of claim 17, wherein the polysilicon layer is shaped to cause the passive optical waveguide device to function as a lens.

19. The passive optical waveguide device of claim 17, wherein the polysilicon layer is shaped to cause the passive optical waveguide device to function as an Echelle grating.

20. The passive optical waveguide device of claim 17, wherein an optical function of the region of static effective mode index is a factor of the shape of the polysilicon layer.

21. The passive optical waveguide device of claim 17, wherein a shape of the region of static effective mode index closely mirrors the shape of the polysilicon layer.

22. The passive optical waveguide device of claim 17, wherein the polysilicon layer includes polySiGe.

23. The passive optical waveguide device of claim 17, further comprising at least one light coupler that applies light to, or from, the optical waveguide.

24. The passive optical waveguide device of claim 17, wherein the optical waveguide has a width, wherein the region of static effective mode index has a substantially uniform light propagation rate across the width of the optical waveguide.

25. The passive optical waveguide device of claim 17, wherein the gate oxide layer is deposited adjacent to an etched portion of the semiconductor layer.

26. The passive optical device of claim 17, wherein the semiconductor layer includes at least one etched portion and at least one unetched portion, and the optical waveguide including a total internal reflection (TIR) boundary between the unetched portion and the etched portion, wherein the TIR boundary constrains light that is flowing within the unetched portion from flowing through the TIR boundary into the etched portion.

27. The passive optical waveguide device of claim 26, wherein the TIR boundary constrains light flowing within the region of static effective mode index.

28. The passive optical waveguide device of claim 26, wherein the TIR boundary constrains light flowing outside of the region of static effective mode index.

30. The method of claim 29, wherein the polysilicon layer is substantially undoped.

31. The method of claim 29, wherein the optical function of the region of static effective mode index is a factor of the shape of the polysilicon layer.

32. The method of claim 29, wherein the optical waveguide has a width, wherein the region of static effective mode index has a substantially uniform light propagation rate across the width of the optical waveguide.

33. The method of claim 29, further comprising doping the polysilicon layer.

34. The method of claim 29, further comprising etching a portion of the semiconductor layer before depositing the gate oxide layer.

35. The method of claim 29, wherein the semiconductor layer includes at least one etched portion and at least one unetched portion, the method further comprising:

creating a total internal reflection (TIR) boundary within the optical waveguide between the unetched portion and the etched portion; and

constraining light from flowing within the unetched portion via the TIR boundary into the etched portion.

36. The method of claim 29, wherein the location of the unetched portion where light is constrained to flow is within the region of static effective mode index.

37. The method of claim 29, wherein the location of the unetched portion where light is constrained to flow is not within the region of static effective mode index.

17. A passive optical waveguide device, comprising:

an optical waveguide formed from a semiconductor layer, a gate oxide layer deposited above the semiconductor layer, and a substantially undoped polysilicon layer formed at least in part from polysilicon and deposited above the gate oxide layer;

wherein the polysilicon layer projects a region of static effective mode index within the optical waveguide, the region of static effective mode index has a different effective mode index than the optical waveguide outside of the region of static effective mode index, wherein the thickness of the optical waveguide is less than or equal to 10 microns, and wherein the effective mode index remains substantially unchanged over time within the region of static effective mode index and applies a substantially unchanging optical function to light travelling through the region of static effective mode index over the lifetime of the passive optical waveguide device.

29. A method of manufacturing a passive optical waveguide device, comprising:

depositing a gate oxide layer above a semiconductor layer formed at least in part from silicon; and

depositing a polysilicon layer formed at least in part from polysilicon above the gate oxide layer,

wherein the polysilicon layer projects a region of static effective mode index within the optical waveguide, the region of static effective mode index has a different effective mode index than the optical waveguide outside of the region of static effective mode index, wherein the thickness of the optical waveguide is less than or equal to 10 microns, and wherein the effective mode index remains substantially unchanged over time within the region of static effective mode index and applies a substantially unchanging optical function to travelling through the region of static effective mode index over the lifetime of the passive optical waveguide device.