Electronic semiconductor control of light in optical waveguide

• US 6,748,125 B2
• Filed: 05/17/2001
• Issued: 06/08/2004
• Est. Priority Date: 05/17/2001
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Sioptical Inc. (Cisco Systems, Inc.)
• Inventors: Deliwala, Shrenik
• Primary Examiner(s): Palmer, Phan T. H.
• Assistant Examiner(s): Doan, Jennifer
• Application Number:
  US09/859,693
• Publication Number:
  US 20030026513A1
• Time in Patent Office: 1,118 Days
• Field of Search: 385/1, 385/2, 385/8, 385/10, 385/14, 385/39, 385/40, 385/129, 385/130
• US Class Current: 385/2
• 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 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 6/12016 characterised by the input or output waveguides, e.g. tapered waveguide ends, coupled together pairs of output waveguides
• CPC Class Codes: G02B 6/12026 characterised by means for reducing the temperature dependence
• CPC Class Codes: G02B 6/12028 based on a combination of materials having a different refractive index temperature dependence, i.e. the materials are used for transmitting light
• 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 6/29325 : of the slab or planar or plate like form, i.e. confinement in a single transverse dimension only integrated circuit planar waveguide arrangements G02B6/12007; specially adapted for lighting G02B6/0011
• 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 6/29391 : Power equalisation of different channels, e.g. power flattening
• CPC Class Codes: G02B 6/29395 : configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02B 6/34 : utilising prism or grating G02B6/293 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

An apparatus and associated method for altering the propagation constant of a region of changable propagation constant in an optical waveguide. The method comprising positioning an electrode of a prescribed electrode shape proximate the waveguide. An altered region of changable propagation constant is projected into the waveguides that correspond, in shape, to the prescribed electrode shape by applying a voltage to the shaped electrode. The propagation constant of the region of changable propagation constant is controlled by varying the voltage.

Claims

1. A method for altering the propagation constant level of a region of changeable propagation constant of a waveguide in an optical device, the method comprising:

positioning a planar electrode proximate the waveguide;

projecting a region of changeable propagation constant into the waveguide that substantially corresponds in shape to the planar electrode shape, by applying a voltage to the planar electrode; and

controlling a propagation constant level of the region of changeable propagation constant by varying the voltage.

2. The method of claim 1, wherein the electrode includes a gate electrode.

3. The method of claim 1, further comprising the step of positioning at least one body contact electrode relative to the planar electrode.

4. The method of claim 1, wherein the projected region of changeable propagation constant is rectangular in shape.

5. The method of claim 1, wherein the projected region of changeable propagation constant is in the shape of an optical prism.

6. The method of claim 1, wherein the projected region of changeable propagation constant is in the shape of a Bragg grating.

7. The method of claim 1, wherein the projected region of changeable propagation constant is in the shape of an Echelle grating.

8. The method of claim 1, wherein the varying the voltage comprises adjusting a voltage component to control the propagation constant level of the region of changeable propagation constant.

9. The method of claim 8, wherein the region of changeable propagation constant acts as a lens with a focal length, and adjusting the voltage component controls the propagation constant level of the region of changeable propagation constant to adjust the focal length of the lens.

10. The method of claim 8, wherein the region of changeable propagation constant acts as a modulator, and adjusting the voltage component modulates the propagation constant level of the region of changeable propagation constant.

11. The method of claim 10, wherein modulation of the propagation constant level phase shifts light flowing through the waveguide.

12. The method of claim 10, wherein modulation of the propagation constant level attenuates light flowing through the waveguide.

13. The method of claim 8, wherein the region of changeable propagation constant acts as a filter, and adjusting the voltage component controls the propagation constant level of the region of changeable propagation constant to adjust filtering of light flowing through the waveguide.

14. The method of claim 8, wherein the region of changeable propagation constant acts as a grating, and adjusting the voltage component controls the propagation constant level of the region of changeable propagation constant to adjust diffraction of light flowing through the waveguide.

15. The method of claim 8, wherein the region of changeable propagation constant comprises a plurality of regions of changeable propagation constant arranged along the waveguide, one or more of the regions of changeable propagation constant act as a mirror, and adjusting the voltage component controls the propagation constant level of the regions of changeable propagation constant to variably equalize a time in which light passes through the waveguide.

16. The method of claim 1, wherein the varying the voltage comprises adjusting a DC bias to compensate for variations in operating parameters of the optical device.

17. The method of claim 16, wherein the operating parameters of the optical device include at least one from the group of:

temperature of the waveguide, age of the optical device, pressure, contact, and vibration.

18. An optical device for altering the propagation constant level of a region of changeable propagation constant of a waveguide, comprising:

a gate electrode having a prescribed electrode shape positioned proximate the waveguide;

a voltage source connected to the electrode for applying voltage to the gate electrode, wherein the voltage causes the gate electrode to project into the waveguide a region of changeable propagation constant corresponding generally in shape to the prescribed shape of the gate electrode; and

a controller that controls the propagation constant level of the region of changeable propagation constant by varying the voltage applied to the gate electrode.

19. The optical device of claim 18, further comprising a body contact electrode positioned proximate the waveguide.

20. The optical device of claim 18, wherein the optical device includes a metal oxide semiconductor capacitor (MOSCAP).

21. The optical device of claim 18, wherein the optical device is a field effect transistor (FET).

22. The optical device of claim 18, wherein modulation of the propagation constant level of the region of changeable propagation constant of the waveguide results in phase modulation of light flowing through the waveguide.

23. The optical device of claim 18, wherein modulation of the propagation constant level of the region of changeable propagation constant of the waveguide amplitude modulates light flowing through the waveguide.

24. The optical device of claim 18, comprising any group III or group V semiconductor.

25. A computer readable medium containing software that controls a planar electrode having a prescribed shape positioned proximate a waveguide, said software when executed by a processor causes the processor to perform the steps of:

projecting a region of changeable propagation constant into the waveguide that corresponds in shape to the prescribed shape, by applying a voltage to the electrode; and

controlling a propagation constant level of the region of changeable propagation constant by varying the voltage.

26. An optical device that modifies an input optical signal in order to generate an output optical signal, comprising:

a waveguide that includes an input port wherein the input optical signal is introduced into the waveguide, an output port wherein the output optical signal exits the waveguide, and a region of changeable propagation constant disposed along a length of the waveguide and between the input port and the output port, wherein the input optical signal is guided by total internal reflection in the waveguide, and the waveguide is formed at least in part from an active semiconductor;

a first electrode positioned proximate a first surface of the region of changeable propagation constant and electrically separated from the active semiconductor;

a second electrode in electrical contact with the active semiconductor and disposed on a first side of the region of changeable propagation constant;

a two-dimensional electron (hole) gas (2DEG) having a free carrier distribution that is formed on at least a portion of the first surface of the region of changeable propagation constant when a voltage is applied between the first electrode and the second electrode; and

wherein variation of the voltage causes a corresponding variation of the free carrier distribution which, in turn, causes corresponding variation of a propagation constant level in the region of changeable propagation constant.

27. The optical device of claim 26, further comprising a third electrode in electrical contact with the active semiconductor disposed on a second side of the region of changeable propagation constant opposite the first side;

wherein the second and third electrodes are electrically coupled to a common potential.

28. The optical device of claim 27, further comprising a field effect transistor (FET) portion that includes the first, second, and third electrodes.

29. The optical device of claim 28, wherein the FET is selected from the group of metal-oxide-semiconductor FET (MOSFET), metal-electrical insulator-semiconductor FET (MISFET), a metal semiconductor field effect transistor (MESFET), a high electron mobility transistor (HEMT), or a modulation doped FET (MODFET).

30. The optical device of claim 27, wherein the body contact electrode includes the second electrode and the third electrode, and the second and third electrodes are both located above the waveguide and on opposed sides of the first electrode.

31. The optical device of claims 26 or 27, wherein the variation of a voltage component adjusts the propagation constant level.

32. The optical device of claim 31, wherein the region of changeable propagation constant acts as a lens with a focal length, and adjusting the voltage component controls the propagation constant level of the region of changeable propagation constant to adjust the focal length of the lens.

33. The optical device of claim 31, wherein the region of changeable propagation constant acts as a modulator, and adjusting the voltage component modulates the propagation constant level of the region of changeable propagation constant.

34. The optical device of claim 33, wherein modulation of the propagation constant level introduces phase shifts on light flowing through the waveguide.

35. The optical device of claim 33, wherein modulation of the propagation constant level attenuates light flowing through the waveguide.

36. The optical device of claim 31, wherein the region of changeable propagation constant acts as a filter, and adjusting the voltage component controls the propagation constant level of the region of changeable propagation constant to adjust the filtering of light flowing through the waveguide.

37. The optical device of claim 31, wherein the region of changeable propagation constant acts as a grating, and adjusting the voltage component controls the propagation constant level of the region of changeable propagation constant to adjust diffraction of light flowing through the waveguide.

38. The optical device of claim 31, wherein the region of changeable propagation constant comprises a plurality of regions of changeable propagation constant arranged along the waveguide, one or more of the regions of changeable propagation constant act as a mirror, and adjusting the voltage component controls the propagation constant level of the regions of changeable propagation constant to variably delay a time in which light passes through the waveguide.

39. The optical device of claim 31, wherein the variation of a voltage component compensates for variations in operating parameters of the optical device.

40. The optical device of claim 39, wherein the operating parameters of the optical device include at least one from the group of:

temperature of the waveguide, optical device age, optical device characteristics, pressure, contact, and vibration.

41. The optical device of claims 26 or 27, wherein the 2DEG is arranged in a plane that is oriented substantially parallel to said length.

42. The optical device of claim 26, further comprising a metal oxide capacitor (MOSCAP) portion.

43. The optical device of claim 42, wherein a body contact electrode is positioned below the waveguide.

44. The optical device of claim 26, wherein the waveguide comprises any group III or group V semiconductor.

45. The optical device of claim 26, wherein free-carrier induced absorption of the 2DEG layer is varied by changing the voltage applied to the first electrode, and wherein light flowing through the waveguide is variably modulated in response to the voltage applied to the first electrode.

46. The optical device of claim 45, wherein the modulation includes attenuation.

47. The optical device of claim 45, wherein the free-carrier induced absorption of the 2DEG layer is varied by changing the voltage applied to the first electrode, and wherein light flowing through the waveguide is deflected to a variable focal length in response to the voltage applied to the first electrode.

48. The optical device of claim 26, wherein the free-carrier induced absorption of the 2DEG layer is varied by changing the voltage applied to the first electrode, and wherein light flowing through the waveguide is variably filtered in response to the voltage applied to the first electrode.

49. An optical device, comprising:

a semiconductor structure comprising a waveguide that permits formation of an optical region extending within the waveguide substantially along an axis of propagation of light within the waveguide, the waveguide has a planar surface that extends within the semiconductor structure, and an electrode that is substantially parallel to the planar surface that can be electrically biased to either establish, or limit the formation of, a free carrier distribution layer along the planar surface;

wherein the electrode is mounted relative to, but electrically insulated from, the waveguide, wherein the free carrier distribution layer is formed by applying electrical potential to the electrode; and

a first body contact mounted relative to, and in electrical contact with, the waveguide.

50. The optical device of claim 49, wherein modulation of the electrode causes a corresponding modulation of the free carrier distribution layer which, in turn, results in a corresponding modulation of a propagation constant in a region of changeable propagation constant of the waveguide.

51. The optical device of claim 50, wherein modulation of the propagation constant level of the region of changeable propagation constant phase modulates light flowing through the waveguide.

52. The optical device of claim 50, wherein modulation of the propagation constant level of the region of changeable propagation constant amplitude modulates or attenuates light flowing through the waveguide.

53. The optical device of claim 49, wherein the free carrier distribution layer is in a plane that is oriented substantially parallel to said axis.

54. The optical device of claim 49, further comprising an electrical insulator that separates the electrode from the waveguide.

55. The optical device of claim 49, wherein the waveguide comprises any group III or group V semiconductor.

56. A method for generating a changed output optical signal by passing an input optical signal through a waveguide, comprising:

providing a gate electrode proximate the waveguide;

providing a body contact electrode proximate the waveguide;

applying the input optical signal to the waveguide;

applying a prescribed voltage to the gate electrode that generates a region of changeable propagation constant in the waveguide; and

generating the changed output optical signal in response to the input optical signal.