Electro-optical phased array beam modulator

• US 6,128,421 A
• Filed: 02/22/1999
• Issued: 10/03/2000
• Est. Priority Date: 02/22/1999
• Status: Expired due to Fees

• Current Assignee: Rodger Allen Roberts
• Original Assignee: Rodger Allen Roberts
• Inventors: Roberts, Rodger Allen
• Primary Examiner(s): Palmer, Phan T. H.
• Application Number:
  US09/255,514
• Time in Patent Office: 589 Days
• Field of Search: 385/3, 385/8, 385/2, 385/4, 385/9, 385/37, 385/14, 385/40, 385/1, 385/147, 359/223, 359/224, 359/291, 359/251, 359/298, 359/846, 372/44, 372/46, 342/368, 342/158, 342/372
• US Class Current: 385/3
• CPC Class Codes: G02F 1/2955 by controlled diffraction or phased-array beam steering controlled diffraction for optical waveguide switching G02F1/313

Abstract

An electro-optical phased array beam modulator is an apparatus for modulating a polarized coherent light source to produce a directionally controlled output beam which can be continuously steered in two separate dimensions by two independently controlled input control signals. It includes a waveguide bundle comprising a multiplicity of similar phase modulator elements with an input end into which polarized coherent light is received and an emitting end on which is located an emitting array from which phase shifted light emerges. It includes an electronic control circuit to convert two input control signals into four corner voltages, which are applied across a resistor grid array and then linearly distributed to the individual phase modulator elements by means of column and row resistor elements, so as to produce a planar voltage distribution pattern of transverse voltages applied across the individual phase modulator elements, corresponding to the required direction of the output beam defined by the two input control signals. A phase shift is induced in the light passing through each phase modulator element proportional to the magnitude of such transverse voltage and the length over which it is applied. Constructive and destructive interference of the light occurs as it emerges from the emitting elements of the emitting array, forming a wave front, the orientation of which is dependent upon the combined effect of the phase shift pattern induced in all the phase modulator elements by such planar voltage distribution pattern.

Claims

1. An apparatus for producing, from a polarized coherent light source, an output beam which can be steered in two dimensions by means of two input control signals, comprising:

a) a waveguide bundle with an input end and an emitting end, comprising;

a multiplicity of similar phase modulator elements each of which comprises;

a waveguide of an electro-optical material;

an input port at the input end of said waveguide to receive the polarized coherent light;

an emitting element at the emitting end of said waveguide to allow phase shifted light to emerge;

a control voltage electrode electrically connected to a resistor grid array; and

a base voltage electrode electrically connected to a base bias grid;

said control voltage electrode and said base voltage electrode running along the length of said waveguide and comprising the means for applying a transverse voltage across said waveguide, by which a phase shift in the light passing through said waveguide is induced proportional to the magnitude of the transverse voltage and the effective length over which the transverse voltage is applied; and

an emitting array at the emitting end comprising a regular array formed from said emitting elements, from which the output beam is produced by the interference of the emerging phase shifted light;

b) an electronic control circuit comprising the means for receiving the two input control signals, providing a base bias voltage and producing four corner voltages, which corner voltages are interrelated in such a way that when said four corner voltages are applied across four corner voltage terminals of said resistor grid array, said four corner voltages produce a substantially planar voltage distribution pattern of the transverse voltages across said emitting array, the orientation of which substantially planar voltage distribution pattern is consistent with the required direction of the output beam defined by the two input control signals;

c) said resistor grid array comprising the means for creating substantially linear voltage gradients within said resistor grid array when the corner voltages are applied to said corner voltage terminals and for applying a separate waveguide control voltage to each of said control voltage electrodes such that the resulting voltage pattern of the transverse voltages applied individually across each of said waveguides is substantially linear along any row and any column in said emitting array, and which resistor grid array comprises the following elements electrically connected together in a grid;

said corner voltage terminals;

a multiplicity of row resistor elements all of substantially the same resistance; and

a multiplicity of column resistor elements all of substantially the same resistance, which resistance is much lower than that of said row resistor elements, in order to minimize deviations from linearity in the planar voltage distribution pattern; and

d) said base bias grid comprising the means for applying the base bias voltage to all said base voltage electrodes.

2. The apparatus of claim 1, wherein the polarized coherent light source is received at the input end of said waveguide bundle at substantially the same phase angle across the input end.

3. The apparatus of claim 1, wherein the corner voltages consist of a reference control voltage and three analog control voltages and wherein the reference control voltage is grounded to the same electrical ground as said electronic control circuit.

4. The apparatus of claim 1, wherein the base bias voltage is grounded to the same electrical ground as said electronic control circuit.

5. The apparatus of claim 1, wherein the corner voltages consist of a reference control voltage and three analog control voltages and wherein said electronic control circuit comprises the means for:

a) grounding both the reference control voltage and the base bias voltage to the electrical ground of said electronic control circuit; and

b) converting the two input control signals into the three analog control voltages, referred to as the second, third and fourth corner voltages, in such a way that;

the second corner voltage is substantially proportional to the first input control signal;

the third corner voltage is substantially proportional to the second input control signal; and

the fourth corner voltage is substantially equal to the sum of the second corner voltage and the third corner voltage.

6. The apparatus of claim 1 wherein the corner voltages consist of a reference control voltage and three analog control voltages and wherein said electronic control circuit comprises the means for applying a reverse tilt to the planar voltage distribution pattern, thereby permitting the scanning range to extend to all four quadrants of a projection plane, by:

a) grounding the base bias voltage to the electrical ground of said electronic control circuit;

b) converting the two input control signals into a first intermediate signal and a second intermediate signal such that;

the first intermediate signal is substantially proportional to the amount by which the first input control signal differs from the midpoint of its operating range, and

the second intermediate signal is substantially proportional to the amount by which the second input control signal differs from the midpoint of its operating range;

c) deriving one of three values for the reference control voltage depending on the relative values of the first intermediate signal and the second intermediate signal; and

d) converting the first intermediate signal, the second intermediate signal and the reference control voltage into the three analog control voltages, referred to as the second, third and fourth corner voltages, in such a way that;

the second corner voltage is substantially equal to the sum of the reference control voltage and the first intermediate signal;

the third corner voltage is substantially equal to the sum of the reference control voltage and the second intermediate signal; and

the fourth corner voltage is substantially equal to the sum of the reference control voltage, the first intermediate signal and the second intermediate signal.

7. The apparatus of claim 1, wherein said electronic control circuit comprises a programmable controller programmed to convert the two input control signals into the corner voltages.

8. The apparatus of claim 7, wherein said programmable controller comprises the means for receiving the two input control signals in a digital form.

9. The apparatus of claim 7, wherein said programmable controller comprises the means for applying a reverse tilt to the planar voltage distribution pattern, thereby permitting the scanning range to extend to all four quadrants of a projection plane.

10. The apparatus of claim 7, wherein said programmable controller comprises the means for applying trigonometric error compensation to the corner voltages.

11. The apparatus of claim 1, wherein said electronic control circuit comprises the means for receiving two continuously variable input control signals and converting them in such a way that the output beam can be controlled continuously over its operating range.

12. The apparatus of claim 1, wherein said electronic control circuit comprises the means for receiving two independently variable input control signals and converting them in such a way that the movement of the output beam in the direction of one axis of a projection plane is substantially independent of its movement along the other axis.

13. The apparatus of claim 1, wherein said electronic control circuit is fabricated on to an end of a waveguide assembly, which waveguide assembly comprises said waveguide bundle and an outer casing surrounding said waveguide bundle.

14. The apparatus of claim 1, wherein said resistor grid array is fabricated on to an end of a waveguide assembly, which waveguide assembly comprises said waveguide bundle and an outer casing surrounding said waveguide bundle.

15. The apparatus of claim 1, wherein said base bias grid is fabricated on to an end of a waveguide assembly, which waveguide assembly comprises said waveguide bundle and an outer casing surrounding said waveguide bundle.

16. The apparatus of claim 1, wherein said phase modulator elements are essentially parallel to one another and are embedded in a solid matrix structure.

17. The apparatus of claim 1, wherein the entire apparatus is an integrated solid state device.

18. The apparatus of claim 1, wherein said waveguide comprises a central core of substantially circular cross-section.

19. The apparatus of claim 1, wherein said waveguide comprises a central core of substantially hexagonal cross-section.

20. The apparatus of claim 1, wherein said electro-optical material of said waveguide is comprised of lead lanthanum zirconate titanate.

21. The apparatus of claim 20, wherein said lead lanthanum zirconate titanate includes trace amounts of barium and strontium as stabilizing agents.

22. The apparatus of claim 1, wherein said electro-optical material of said waveguide is comprised of lead lanthanum stannate zirconate titanate.

23. The apparatus of claim 22, wherein said lead lanthanum stannate zirconate titanate includes trace amounts of barium and strontium as stabilizing agents.

24. The apparatus of claim 1, wherein said phase modulator elements further include a non-reflective coating at their emitting ends.

25. The apparatus of claim 1 wherein said emitting array is a two dimensional emitting array.

26. The apparatus of claim 25, wherein operable emitting elements of said emitting array form a hexagonal shape.

27. The apparatus of claim 1, wherein said emitting array is a rectangular emitting array with m number of rows and n number of columns.

28. The apparatus of claim 27, wherein:

the number of rows is equal to the number of columns;

said emitting array is a square emitting array; and

said resistor grid array is a square resistor grid array.

29. The apparatus of claim 27, wherein:

the number of rows is equal to the number of columns;

said emitting array is an offset square emitting array; and

said resistor grid array is an offset square resistor grid array and further includes half value row resistor elements.

30. The apparatus of claim 1, wherein the phase modular elements are substantially identical to one another.

31. The apparatus of claim 1, wherein the intensity of the polarized coherent light source is substantially the same across the input end of said waveguide bundle.

32. The apparatus of claim 1, which further includes an attenuating filter located at an end of said waveguide bundle, said attenuating filter comprising the means for modifying the effective shape of the emitting array by attenuating the light passing through said attenuating filter according to a predetermined attenuation pattern across its surface.

33. The apparatus of claim 1, wherein the electrical connection between said resistor grid array and each of said control voltage electrodes further includes the means for amplifying the electrical signal between said resistor grid array and each of said control voltage electrodes.

34. An apparatus for producing, from a polarized coherent light source, an output beam which can be steered in two dimensions by means of two input control signals, comprising:

a) a waveguide stack with an input end and an emitting end, comprising;

a plurality of similar planar phase modulator elements, stacked on top of one another so as to form said waveguide stack, each of which planar phase modulator elements comprises;

a planar thin film waveguide of an electro-optical material;

a longitudinal input port at the input end of said planar thin film waveguide to receive the polarized coherent light;

a longitudinal emitting element at the emitting end of said planar thin film waveguide to allow phase shifted light to emerge;

a planar control voltage electrode, the opposite sides of which are each electrically connected to opposite points of a resistor grid array; and

a planar base voltage electrode electrically connected to a base bias grid;

said planar control voltage electrode and said planar base voltage electrode running along opposite surfaces of said planar thin film waveguide and comprising the means for applying a linearly varying transverse voltage across said planar thin film waveguide, by which, linearly varying phase shifts in the light passing through said planar thin film waveguide are induced, which phase shifts at any point along said longitudinal emitting element are proportional to the magnitude of the linearly varying transverse voltage at that point and the effective length over which the linearly varying transverse voltage is applied; and

an emitting array at the emitting end comprising a linear array of said longitudinal emitting elements, from which the output beam is produced by the interference of the emerging phase shifted light;

b) an electronic control circuit comprising the means for receiving the two input control signals, providing a base bias voltage and producing four corner voltages, which four corner voltages are interrelated in such a way that when said four corner voltages are applied across four corner voltage terminals of said resistor grid array, said four corner voltages produce a substantially planar voltage distribution pattern of the transverse voltages across the surface of said emitting array, the orientation of which substantially planar voltage distribution pattern is consistent with the required direction of the output beam defined by the two input control signals;

c) said resistor grid array comprising the means for creating substantially linear voltage gradients within two columns of said resistor grid array when the four corner voltages are applied to said four corner voltage terminals and for applying separate waveguide control voltages to side electrodes on opposite sides of each of said planar control voltage electrodes, and which resistor grid array comprises the following elements electrically connected together in a grid;

said corner voltage terminals;

a multiplicity of column resistor elements arranged in said two columns, which column resistor elements are all of substantially the same resistance, which resistance, in order to minimize deviations from linearity in the planar voltage distribution pattern, is much lower than the resistance of each of said planar control voltage electrodes between the side electrodes on opposite sides of each of said planar control voltage electrodes; and

d) said base bias grid comprising the means for applying the base bias voltage to all said planar base voltage electrodes.

35. An apparatus for producing, from a polarized coherent light source, an output beam which can be steered in two dimensions by means of a multiplicity of separate transverse voltages received from a control and distribution circuit, comprising a waveguide bundle with an input end and an output end, which waveguide bundle comprises:

a) a multiplicity of similar phase modulator elements each of which comprises;

a waveguide of an electro-optical material;

an input port at the input end of said waveguide to receive the polarized coherent light;

an emitting element at the emitting end of said waveguide to allow phase shifted light to emerge;

a control voltage electrode comprising the means for receiving a waveguide control voltage from the control and distribution circuit; and

a base voltage electrode comprising the means for receiving a base bias voltage from the control and distribution circuit;

said control voltage electrode and said base voltage electrode running along the length of said waveguide and comprising the means for applying the transverse voltage, across said waveguide, by which a phase shift in the light passing through said waveguide is induced proportional to the magnitude of the transverse voltage and the effective length over which the transverse voltage is applied; and

b) an emitting array at the emitting end comprising a regular array formed from said emitting elements, from which the output beam is produced by the interference of the emerging phase shifted light.

36. The apparatus of claim 35, wherein the phase modular elements are substantially identical to one another.

37. A control and distribution circuit, for producing a multiplicity of separate transverse voltages from two input control signals and distributing the transverse voltages individually across the waveguide of each of a multiplicity of similar phase modulator elements of a waveguide bundle, in order to steer an output beam produced by said waveguide bundle from a polarized coherent light source, comprising:

a) an electronic control circuit comprising the means for receiving the two input control signals. providing a base bias voltage and producing four corner voltages, which corner voltages are interrelated in such a way that when said four corner voltages are applied across four corner voltage terminals of a resistor grid array said four corner voltages produce a substantially planar voltage distribution pattern of the transverse voltages across an emitting array of said waveguide bundle, the orientation of which substantially planar voltage distribution pattern is consistent with the required direction of the output beam defined by the two input control signals;

b) said resistor grid array comprising the means for creating substantially linear voltage gradients within said resistor grid array when the corner voltages are applied to said corner voltage terminals and for applying a separate waveguide control voltage to the control voltage electrode of each of said phase modulator elements such that the resulting voltage pattern of the transverse voltages applied individually across each of said waveguides is substantially linear along any row and any column in said emitting array, and which resistor grid array comprises the following elements electrically connected together in a grid;

said corner voltage terminals;

a multiplicity of row resistor elements all of substantially the same resistance; and

a multiplicity of column resistor elements all of substantially the same resistance, which resistance is much lower than that of said row resistor elements, in order to minimize deviations from linearity in the planar voltage distribution pattern; and

c) a base bias grid comprising the means for applying the base bias voltage to all base voltage electrodes of said phase modulator elements.

38. The apparatus of claim 37, wherein the corner voltages consist of a reference control voltage and three analog control voltages and wherein the reference control voltage is grounded to the same electrical ground as said electronic control circuit.

39. The apparatus of claim 37, wherein the base bias voltage is grounded to the same electrical ground as said electronic control circuit.

40. The apparatus of claim 37, wherein the corner voltages consist of a reference control voltage and three analog control voltages and wherein said electronic control circuit comprises the means for:

a) grounding both the reference control voltage and the base bias voltage to the electrical ground of said electronic control circuit; and

b) converting the two input control signals into the three analog control voltages, referred to as the second, third and fourth corner voltages, in such a way that;

the second corner voltage is substantially proportional to the first input control signal;

the third corner voltage is substantially proportional to the second input control signal; and

the fourth corner voltage is substantially equal to the sum of the second corner voltage and the third corner voltage.

41. The apparatus of claim 37, wherein the corner voltages consist of a reference control voltage and three analog control voltages and wherein said electronic control circuit comprises the means for applying a reverse tilt to the planar voltage distribution pattern, thereby permitting the scanning range to extend to all four quadrants of a projection plane, by:

a) grounding the base bias voltage to the electrical ground of said electronic control circuit;

b) converting the two input control signals into a first intermediate signal and a second intermediate signal such that;

the first intermediate signal is substantially proportional to the amount by which the first input control signal differs from the midpoint of its operating range, and

the second intermediate signal is substantially proportional to the amount by which the second input control signal differs from the midpoint of its operating range;

c) deriving one of three values for the reference control voltage depending on the relative values of the first intermediate signal and the second intermediate signal; and

d) converting the first intermediate signal, the second intermediate signal and the reference control voltage into the three analog control voltages, referred to as the second, third and fourth corner voltages, in such a way that;

the second corner voltage is substantially equal to the sum of the reference control voltage and the first intermediate signal;

the third corner voltage is substantially equal to the sum of the reference control voltage and the second intermediate signal; and

the fourth corner voltage is substantially equal to the sum of the reference control voltage, the first intermediate signal and the second intermediate signal.

42. The apparatus of claim 37, wherein said electronic control circuit comprises a programmable controller programmed to convert the two input control signals into the corner voltages.

43. The apparatus of claim 42, wherein said programmable controller comprises the means for receiving the two input control signals in a digital form.

44. The apparatus of claim 42, wherein said programmable controller comprises the means for applying a reverse tilt to the planar voltage distribution pattern, thereby permitting the scanning range to extend to all four quadrants of a projection plane.

45. The apparatus of claim 42, wherein said programmable controller comprises the means for applying trigonometric error compensation to the corner voltages.

46. The apparatus of claim 37, wherein the electrical connection between said resistor grid array and each of said control voltage electrodes further includes the means for amplifying the electrical signal between said resistor grid array and each of said control voltage electrodes.

47. An apparatus for producing, from a polarized coherent light source, an output beam which can be steered in one dimension by means of one input control signal, comprising:

a) a waveguide bundle with an input end and an emitting end, comprising;

a multiplicity of similar phase modulator elements each of which comprises;

a waveguide of an electro-optical material;

an input port at the input end of said waveguide to receive the polarized coherent light;

an emitting element at the emitting end of said waveguide to allow phase shifted light to emerge;

a control voltage electrode electrically connected to a resistor grid array; and

a base voltage electrode electrically connected to a base bias grid;

said control voltage electrode and said base voltage electrode running along the length of said waveguide and comprising the means for applying a transverse voltage across said waveguide, by which a phase shift in the light passing through said waveguide is induced proportional to the magnitude of the transverse voltage and the effective length over which the transverse voltage is applied; and

an emitting array at the emitting end comprising a regular array formed from said emitting elements, from which the output beam is produced by the interference of the emerging phase shifted light;

b) an electronic control circuit comprising the means for receiving the input control signal, providing a base bias voltage and producing two corner voltages, which two corner voltages consist of a reference control voltage and an analog control voltage, which are interrelated in such a way that when the two corner voltages are applied across two corner voltage terminals of said resistor grid array, said two corner voltages produce a substantially planar voltage distribution pattern of the transverse voltages across said emitting array, the orientation of which substantially planar voltage distribution pattern is consistent with the required direction of the output beam defined by the input control signal;

c) said resistor grid array comprising the means for creating substantially linear voltage gradients within said resistor grid array when the two corner voltages are applied to said two corner voltage terminals and for applying a separate waveguide control voltage to each of said control voltage electrodes such that the resulting voltage pattern of the transverse voltages applied individually across each of said waveguides is substantially linear along any row and any column in said emitting array, and which resistor grid array comprises the following elements electrically connected together in a grid;

said two corner voltage terminals; and

a multiplicity of row resistor elements all of substantially the same resistance; and

d) said base bias grid comprising the means for applying the base bias voltage to all said base voltage electrodes.

48. The apparatus of claim 47, wherein the phase modular elements are substantially identical to one another.

49. The apparatus of claim 47, wherein the reference control voltage is grounded to the same electrical ground as said electronic control circuit.

50. The apparatus of claim 47, wherein the base bias voltage is grounded to the same electrical ground as said electronic control circuit.

51. The apparatus of claim 47, wherein said electronic control circuit comprises the means for:

a) grounding both the reference control voltage and the base bias voltage to the electrical ground of said electronic control circuit; and

b) converting the input control signal into the analog control voltage in such a way that the analog control voltage is substantially proportional to the input control signal.

52. The apparatus of claim 47, wherein said electronic control circuit comprises the means for applying a reverse tilt to the planar voltage distribution pattern, thereby permitting the scanning range to extend to two quadrants of a projection plane, by:

a) grounding the base bias voltage to the electrical ground of said electronic control circuit,

b) converting the input control signal into the analog control voltage in such a way that the analog control voltage is substantially proportional to the amount by which the input control signal differs from the midpoint of its operating range; and

c) deriving one of two values for the reference control voltage depending on whether the amount by which the input control signal differs from the midpoint of its operating range is positive or negative.

53. An apparatus for producing, from a polarized coherent light source, an output beam which can be steered in one dimension by means of one input control signal, comprising:

a) a waveguide stack with an input end and an emitting end, comprising at least one planar phase modulator element, which planar phase modulator element comprises;

a planar thin film waveguide of an electro-optical material;

a longitudinal input port at the input end of said planar thin film waveguide to receive the polarized coherent light;

a longitudinal emitting element at the emitting end of said planar thin film waveguide to allow phase shifted light to emerge, from which the output beam is produced by the interference of the emerging phase shifted light;

a planar control voltage electrode, the opposite sides of which are each electrically connected to an electronic control circuit; and

a planar base voltage electrode electrically connected to a base bias grid;

said planar control voltage electrode and said planar base voltage electrode running along opposite surfaces of said planar thin film waveguide and comprising the means for applying a linearly varying transverse voltage across said planar thin film waveguide, by which, linearly varying phase shifts in the light passing through said planar thin film waveguide are induced, which phase shifts at any point along said longitudinal emitting element are proportional to the magnitude of the linearly varying transverse voltage at that point and the effective length over which the linearly varying transverse voltage is applied,

b) an electronic control circuit comprising the means for receiving the input control signal, providing a base bias voltage and producing two corner voltages, which two corner voltages are interrelated in such a way that when said two corner voltages are applied to opposite sides of each of said planar control voltage electrodes, said two corner voltages produce a substantially linearly varying transverse voltage across said planar thin film waveguide, the gradient of which substantially linearly varying transverse voltage is consistent with the required direction of the output beam defined by the input control signal; and

c) said base bias grid comprising the means for applying the base bias voltage to said planar base voltage electrode.