Self-aligning modulator method and associated apparatus

• US 6,608,945 B2
• Filed: 05/17/2001
• Issued: 08/19/2003
• Est. Priority Date: 05/17/2001
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Optronx Inc.
• Inventors: Deliwala, Shrenik
• Primary Examiner(s): Ullah, Akm E.
• Assistant Examiner(s): Doan, Jennifer
• Application Number:
  US09/859,769
• Publication Number:
  US 20030026514A1
• Time in Patent Office: 824 Days
• Field of Search: 385/2, 385/3, 385/8, 385/10, 385/11, 385/15, 385/24, 385/27, 385/36, 385/40, 385/50, 356/477, 356/161
• 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 6/272 : comprising polarisation means for beam splitting and combining
• 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

A self-aligned optical modulator that modulates an input optical signal in order to generate a modulated output optical signal includes an optical modulator device including a waveguide, a first modulating electrode, a second modulating electrode, and a two-dimensional electron (hole) gas (2DEG) proximate the first modulating electrode, the waveguide includes an input port wherein the input optical signal is introduced into the waveguide, an output port wherein the modulated output optical signal exits the waveguide, and a region of modulating propagation constant disposed along a first 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. The first modulating electrode is positioned proximate a first surface of the region of modulating propagation constant and electrically separated from an active semiconductor.

Claims

1. A self-aligned optical modulator that modulates an input optical signal in order to generate a modulated output optical signal, comprising:

an optical modulator device including a waveguide, a first modulating electrode, a second modulating electrode, and a two-dimensional electron (hole) gas (2DEG) proximate the first modulating electrode, the waveguide includes an input port wherein the input optical signal is introduced into the waveguide, an output port wherein the modulated output optical signal exits the waveguide, and a region of modulating propagation constant disposed along a first 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;

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

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

the two-dimensional electron (hole) gas (2DEG) proximate the first modulating electrode has a free carrier distribution that is formed on the first surface when a modulating voltage is applied between the first modulating electrode and the second modulating electrode, wherein modulation of the voltage by the optical modulation device causes a corresponding modulation of the free carrier distribution which, in turn, causes corresponding modulation of a propagation constant level in the region of modulating propagation constant;

a first deflector that deflects light in a first lateral direction within the waveguide;

a second deflector configured to deflect light in a second lateral direction towards the waveguide wherein the deflection of the first deflector or the second deflector acts to direct light approaching the region of modulating propagation constant towards the region of modulating propagation constant.

2. The self-aligned optical modulator of claim 1, wherein said first deflector adjustably deflects light by a first deflection angle and comprises:

a first deflecting electrode;

a second deflecting electrode;

a two-dimensional electron (hole) gas (2DEG) proximate the first deflecting electrode and having a free carrier distribution that is formed when a first deflecting voltage is applied between the first and second deflecting electrodes;

wherein variation of the first deflecting voltage causes a corresponding change in the free carrier distribution of the 2DEG proximate the first deflectig electrode and an adjustment of the first deflection angle.

3. The self-aligned optical modulator of claim 2, wherein said second deflector adjustably deflects light by a second deflection angle and comprises:

a third deflecting electrode;

a fourth deflecting electrode;

a two-dimensional electron (hole) gas (2DEG) proximate the third deflecting electrode and having a free carrier distribution that is formed when a second deflecting voltage is applied between the third and fourth deflecting electrodes;

wherein variation of the second deflecting voltage causes a corresponding change in the free carrier distribution of the 2DEG proximate the third deflecting electrode and an adjustment of the second deflection angle.

4. The self-aligned optical modulator or claim 3, wherein said first deflector further comprises a first region of deflecting propagation constant, wherein variation of the first deflecting voltage causes a corresponding adjustment of a propagation constant level in the first region of deflecting propagation constant.

5. The self-aligned optical modulator of claim 4, wherein said second deflector further comprises a second region of deflecting propagation constant, wherein variation of the second deflecting voltage causes a corresponding adjustment of a propagation constant level in the second region of deflecting propagation constant.

6. The self-aligned optical modulator of claim 5, wherein the first region of deflecting propagation constant is disposed along a second length f the waveguide between the input and the output port.

7. The self-aligned optical modulator of claim 6, wherein the second region of deflecting propagation constant is disposed along a third length of the waveguide and between the first and second lengths.

8. The self-aligned optical modulator of claim 7, wherein the waveguide is a slab waveguide.

9. The self-aligned optical modulator of claim 1, 2 or 3, wherein said optical modulator device, said first deflector and said second deflector are disposed on a common semiconductor substrate.

10. The self-aligned optical modulator of claim 1, further comprising a third modulating electrode in electrical contact with the active semiconductor disposed on a second side of the region of modulating propagation constant opposite the first side;

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

11. The self-aligned optical modulator of claim 10, further comprising a field effect transistor (FET) portion that includes the first, second, and third electrodes.

12. The self-aligned optical modulator of claim 11, wherein the FET portion is from one of 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).

13. The self-aligned optical modulator of claim 1, wherein said modulation of the propagation constant level phase modulates the input optical signal.

14. The self-aligned optical modulator of claim 1, wherein said modulation of the propagation constant level amplitude modulates the input optical signal.

15. The self-aligned optical modulator of claim 14, wherein said modulation of the propagation constant level attenuates the input optical signal.

16. The self-aligned optical modulator of claim 1 or 10, wherein the 2DEG is oriented in a plane that is substantially parallel to said length.

17. The self-aligned optical modulator of claim 1, further comprising a metal oxide semiconductor capacitor (MOSCAP) portion.

18. The self-aligned optical modulator of claim 1, further comprising a lens that focuses light passing through the first deflector and the second deflector towards the optical modulator device.

19. The self-aligned optical modulator of claim 1, further comprising a lens that focuses light flowing from the optical modulator device to the output port.

20. The self-aligned optical modulator of claim 18 or 19, wherein said lens comprises:

a first focusing electrode;

a second focusing electrode;

a two-dimensional electron (hole) gas (2DEG) proximate the first focusing electrode and having a free carrier distribution that is formed when a focusing voltage is applied between the first and second focusing electrodes;

wherein variation of the focusing voltage causes a corresponding change in the free carrier distribution of the 2DEG proximate the first focusing electrode and an adjustment of focusing characteristics of the lens.

21. The self-aligned optical modulator of claim 20, wherein said optical modulator device and said lens are disposed on a common semiconductor substrate.

22. The self-aligned optical modulator of claim 21, wherein said lens further comprises a region of focusing propagation constant, wherein variation of the focusing voltage causes a corresponding adjustment of a propagation constant level in the region of focusing propagation constant.

23. The self-aligned optical modulator of claim 22, wherein the region of focusing propagation constant is disposed along a second length of the waveguide between the input port and the output port.

24. The self-aligned optical modulator of claim 23, wherein the waveguide is a slab waveguide.

25. The self-aligned optical modulator of claim 1, wherein the free-carrier distribution of the 2DEG layer is varied by changing the modulating voltage applied to the first modulating electrode, and wherein light flowing through the waveguide is controllably attenuated in response to the voltage applied to the first modulating electrode.

26. A self-aligned optical modulator for modulating the propagation constant level of an optical modulating region of a waveguide, comprising:

an optical modulator device including a waveguide, a gate electrode, and a voltage source, the gate electrode having a prescribed electrode shape positioned proximate the waveguide;

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

a first deflector configured to deflect light in a first lateral direction within the waveguide;

a second deflector configured to deflect light in a second lateral direction within the waveguide wherein the deflection of the first deflector or the second deflector acts to direct light approaching the region of modulating propagation constant towards the region of modulating propagation constant; and

a controller that controls a propagation constant level of the region of modulating propagation constant by varying the voltage applied to the gate electrode to modulate light flowing through the waveguide, the controller also controls operation of the first deflector and the second deflector.

27. The self-aligned optical modulator of claim 26, wherein said propagation constant level modulation phase modulates the input optical signal.

28. The self-aligned optical modulator of claim 26, wherein said propagation constant level modulation amplitude modulates the input optical signal.

29. The self-aligned optical modulator of claim 28, wherein said propagation constant level modulation attenuates the input optical signal.

30. The self-aligned optical modulator of claim 26, wherein a 2DEG is oriented in a plane that is substantially parallel to the region of modulating propagation constant.

31. The self-aligned optical modulator of claim 26, further comprising a field effect transistor (FET) portion including a source electrode and a drain electrode.

32. The self-aligned optical modulator of claim 31, wherein the FET is from one of 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).

33. The self-aligned optical modulator of claim 26, further comprising one or more body contact electrode(s) positioned relative to the waveguide and electrically integrated with an active semiconductor.

34. The self-aligned optical modulator of claim 33, further comprising a metal oxide semiconductor capacitor (MOSCAP) portion that includes the body contact electrode.

35. The self-aligned optical modulator of claim 33, wherein the body contact electrode includes a first body contact electrode and a second body contact electrode, the first body contact electrode, the gate electrode, and the second body contact electrode are located above the waveguide.

36. The self-aligned optical modulator of claim 35, wherein the first body contact electrode is located on an opposed side of the gate electrode from the second body contact electrode, and wherein the waveguide comprises any group III or group V semiconductor.

37. The self-aligned optical modulator of claim 26, further comprising a lens that focuses light passing through the first deflector and the second deflector towards the optical modulator device.

38. The self-aligned optical modulator of claim 26, wherein a free-carrier distribution of a 2DEG layer is varied by changing the voltage applied to the gate electrode, and wherein light flowing through the waveguide is controllably attenuated in response to the voltage applied to the gate electrode.

39. The self-aligned optical modulator of claim 26, further comprising an optical device coupled with a variable coupling to the self-aligned optical modulator.

40. A method for self-aligned optical modulation comprising:

positioning a planar electrode proximate a waveguide;

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

providing for the deflection of light in a first lateral direction within the waveguide;

providing for the deflection of light in a second lateral direction within the waveguide, wherein the deflection in the first lateral direction or the second lateral direction acts to direct light approaching the region of modulating propagation constant towards the region of modulating propagation constant; and

controlling a propagation constant level of the region of modulating propagation constant by varying the voltage to control the modulation of light flowing through the waveguide, and controlling the deflection of light in the first lateral direction or the second lateral direction.

41. The method of claim 40, wherein said modulation of the propagation constant level phase modulates an input optical signal.

42. The method of claim 40, wherein said modulation of the propagation constant level amplitude modulates the input optical signal.

43. The method of claim 42, wherein said modulation of the propagation constant level attenuates the input optical signal.

44. The method of claim 40, further comprising a 2DEG located between the planar electrode and a body contact electrode, wherein the 2DEG is oriented in a plane that is substantially parallel to a length of the region of modulating propagation constant.

45. The method of claim 44, wherein the free-carrier distribution of the 2DEG layer is modulated by changing the voltage applied to the planar electrode, and wherein light flowing through the waveguide is controllably modulated in response to modulating the free-carrier distribution of the 2DEG layer.

46. The method of claim 40, further comprising a field effect transistor (FET) portion including a planar electrode.

47. The method of claim 46, wherein the FET is from one of 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).

48. The method of claim 40, further comprising one or more body contact electrode(s) positioned relative to the waveguide and electrically integrated with the active semiconductor.

49. The method of claim 48, further comprising a metal oxide semiconductor capacitor (MOSCAP) portion including the body contact electrode.

50. The method of claim 48, wherein the body contact electrode is positioned below the waveguide.

51. The method of claim 48, wherein the body contact electrode includes a first body contact electrode and a second body contact electrode, the first body contact electrode, the planar electrode, and the second body contact electrode are located above the waveguide;

and the first body contact electrode is located on an opposed side of the planar electrode from the second body contact electrode.

52. The method of claim 40, wherein the waveguide comprises any group III or group V semiconductor.

53. The method of claim 40, further comprising an optical device coupled with a variable coupling to the self-aligned optical modulator.

54. 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:

project a region of modulating propagation constant into the waveguide that corresponds in shape to a shape of an electrode, by applying a voltage to the electrode; and

providing for the deflection of light in a first lateral direction within the waveguide;

providing for the deflection of light in a second lateral direction within the waveguide, wherein the deflection in the first lateral direction or the second lateral direction acts to direct light approaching the region of modulating propagation constant towards the region of modulating propagation constant; and

controlling a propagation constant level of the region of modulating propagation constant by varying the voltage to control the modulation of light flowing through the waveguide, and controlling the deflection of light in the first lateral direction or the second lateral direction.

55. The computer readable medium of claim 54, wherein said modulation of the propagation constant level phase modulates the input optical signal.

56. A self-aligned optical modulator for modulating light flowing through a waveguide by modulation of a propagation constant level of the waveguide, the self-aligned optical modulator comprising:

a region of modulating propagation constant disposed along a length of the waveguide and defining a region where light is modulated, wherein light is guided within the waveguide by total internal reflection, and the waveguide is formed at least in part from an active semiconductor;

a Field Effect Transistor portion (FET portion) including a gate electrode, a source electrode, and a drain electrode;

the gate electrode is mounted to, but electrically insulated from, the active semiconductor, the drain electrode and the source electrode are held at a substantially common voltage, wherein the gate electrode, the source electrode, and the drain electrode are positioned substantially above the waveguide, the source electrode is located on a substantially opposed side of the gate electrode from the drain electrode;

a two-dimensional electron (hole) gas (2DEG) having a free carrier distribution that is formed on the first surface when a voltage is applied between the gate electrode and the common voltage;

a voltage source connected to the gate electrode for applying the voltage to the gate electrode, wherein the gate electrode projects the region of modulating propagation constant into the waveguide;

a first deflector configured to deflect light in a first lateral direction within the waveguide;

a second deflector configured to deflect light in a second lateral direction within the waveguide wherein the deflection of the first deflector or the second deflector acts to direct light approaching the region of modulating propagation constant towards the region of modulating propagation constant; and

a controller that controls the propagation constant level of the region of modulating propagation constant by varying the voltage applied to the gate electrode to modulate light flowing through the waveguide, the controller also controls the operation of the first deflector and the second deflector.

57. An apparatus for modulating an input optical signal in order to generate a modulated output optical signal, comprising:

a planar electrode positioned proximate the waveguide;

means for modulating a region of modulating propagation constant in the waveguide that substantially corresponds in shape to a shape of the planar electrode, by applying a voltage to the planar electrode; and

means for providing for the deflection of light in a first lateral direction within the waveguide;

means for providing for the deflection of light in a second lateral direction within the waveguide, wherein the deflection in the first lateral direction or the second lateral direction acts to direct light approaching the region of modulating propagation constant towards the region of modulating propagation constant; and

means for controlling a propagation constant level of the region of modulating propagation constant by varying the voltage to control the modulation of light flowing through the waveguide, and controlling the deflection of light in the first lateral direction or the second lateral direction.