Electro-optic waveguide device

• US 5,082,342 A
• Filed: 05/22/1990
• Issued: 01/21/1992
• Est. Priority Date: 11/20/1987
• Status: Expired due to Term

• Current Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Original Assignee: The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Inventors: West, Christopher L., Heaton, John M., Lewis, Meirion F., Wight, David R.
• Primary Examiner(s): Ullah, Akm
• Application Number:
  US07/488,042
• Time in Patent Office: 609 Days
• Field of Search: 350/96.12-96.14, 357/30, 357/17, 372/44
• US Class Current: 385/8
• CPC Class Codes: G02F 1/0154 using electro-optic effects, e.g. linear electro optic [LEO], Pockels, quadratic electro optical [QEO] or Kerr 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]

Abstract

An electro-optic waveguide device (10) comprises an assembly of waveguides (30) connected to a common light input region (41) and forming a common far field diffraction pattern (44). The device (10) comprises an n⁺ GaAs substrate (14) bearing a waveguide lower cladding layer (16) of n⁺ Ga₀.9 Al₀.1 As, which is in turn surmounted by a waveguide core layer (18) of n^- GaAs. The layer (18) has grooves (20) defining the waveguides (30), each of which has a respective Schottky contact (32). Each contact (32) is biased negative with respect to the substrate (14), which reverse biases the respective Schottky diode waveguide structure. The waveguide core layer (18) has electro-optic properties, and its refractive index varies with electric field. The phase of light emerging from each waveguide is therefore independently variable by means of its applied bias voltage. The waveguides (30) are arranged to provide output confined very largely to lowest order spatial modes, so that they produce a single far field diffraction pattern (44). Varying the set of bias voltages applied to the waveguides (30) produces output phase variation which changes the position of the diffraction pattern principal maximum (46) to produce beam steering.

Claims

1. An electro-optic waveguide device of multilayer construction including an array of electrically biasable waveguides of electro-refractive material, said device comprising:

(a) a waveguide core layer having a refractive index and two light confinement layers sandwiching said core layer therebetween, each of said confinement layers having a refractive index lower than said core layer refractive index, said waveguide core layer comprises at least part of a diode structure and said diode structure depletable of charge carriers under a reverse bias applied by means of said confinement layers;

(b) means defining grooving at least partly through said waveguide core layer and for defining individual waveguides, said individual waveguides forming an array;

(c) a grooving medium contained in said waveguides having a refractive index at least 1.5 less than said waveguide core layer refractive index, said means defining grooving and said medium comprising a means for optically isolating adjacent waveguides;

(d) a biasing means for each respective waveguide;

(e) means arranging said waveguides for inhibiting output of unwanted spatial modes; and

(f) said waveguides and said biasing means comprise a means for providing for radiation output from said waveguides to interfere and for generating a far field diffraction pattern having a main lobe steerable across an output region of the device.

2. A device according to claim 1 wherein said waveguides have a width less than 5λ

and centers of adjacent waveguide are less than 20λ

apart, where λ

is a free space operating wavelength of said device.

3. A device according to claim 1 wherein said grooving medium is air.

4. A device according to claim 1 wherein said device is at least partly constructed of successively disposed semiconductor material layers of the Ga_x Al_1-x As system.

5. A device according to claim 4, wherein one of the light confinement layers comprises a Schottky contact to said waveguide core layer.

6. A device according to claim 4, wherein said waveguide core layer is comprised of substantially undoped GaAs and said light confinement layers are comprised of GaAlAs and have mutually opposite conductivity type.

7. A device according to claim 4, wherein one of the light confinement layers is common to each of said waveguides.

8. A device according to claim 4, wherein said waveguide core layer includes a common crystal cleavage plane and each of said waveguides include respective light output surface regions in said common crystal cleavage plane.

9. An electro-optic waveguide device of multilayer construction including an array of electrically biasable waveguides of electro-refractive material, said device comprising:

(a) a waveguide core layer having a refractive index and two light confinement layers sandwiching said core layer therebetween, each of said confinement layers having a refractive index lower than said core layer refractive index, said waveguide core layer comprises at least part of a diode structure and said diode structure depletable of charge carriers under a reverse bias applied by means of said confinement layers;

(b) means defining grooving at least partly through said waveguide core layer and for defining individual waveguides, said individual waveguides forming an array;

(c) a grooving medium contained in said waveguides having a refractive index at least 1.5 less than said waveguide core layer refractive index, said means defining grooving and said medium comprising a means for inhibiting optical coupling between adjacent waveguides;

(d) means arranging said waveguides for inhibiting output of unwanted spatial modes; and

(e) means for biasing said waveguides, said means for biasing said waveguides comprising respective bond pads and conductors connected thereto, said bond pads located around a region of a device containing the waveguides and said conductors extending over a light input region of the device.

10. A device according to claim 9, wherein said waveguides and said biasing means comprise a means for generating a far field diffraction pattern at an input region of an array of receive waveguides, said device further including receive waveguides, said pattern having a main diffraction lobe receivable by any one of said receive waveguides and steerable across said array of receive waveguides.

11. A device according to claim 10 wherein the electro-optic waveguide device is comprised of a semiconductor multilayer structure.

12. A device according to claim 11, wherein said receive waveguides have a minimum relative spacing at said input region.

13. An electro-optic waveguide device of multilayer construction including an array of electrically biasable waveguide of electro-refractive material, said device comprising:

(a) a waveguide core layer having a refractive index and two light confinement layers sandwiching said core layer therebetween, each of said confinement layers having a refractive index lower than said core layer refractive index, said waveguide core layer comprises at least part of a diode structure and said diode structure depletable of charge carriers under a reverse bias applied by means of said confinement layers;

(b) means defining grooving at least partly through said waveguide core layer and for defining individual electro-optic waveguides, said individual electro-optic waveguides forming an array;

(c) a grooving medium contained in said electro-optic waveguides having a refractive index at least 1.5 less than said waveguide core layer refractive index, said means defining grooving and said medium comprising a means for inhibiting optical coupling between adjacent electro-optic waveguides;

(d) means arranging said electro-optic waveguides for inhibiting output of unwanted spatial modes;

(e) an array of receive waveguides having an input region; and

(f) said electro-optic waveguides comprising a means for generating a far field diffraction pattern at said input region of said array of receive waveguides, said diffraction pattern having a main diffraction lobe receivable by any one of the receive waveguides and steerable across said receive waveguide array.

14. A device according to claim 13 wherein the electro-optic waveguides and receive waveguides are formed as a semiconductor multilayer structure.

15. A device according to claim 14 wherein the receive waveguides have a minimum relative spacing at said input region.

16. An electro-optic waveguide device of multilayer construction including an array of electrically biasable waveguides of electro-refractive material, said device comprising:

(a) a waveguide core layer having a refractive index and two light confinement layers sandwiching said core layer therebetween, each of said confinement layers having a refractive index lower than said core layer refractive index, said waveguide core layer comprises at least part of a diode structure and said diode structure depletable of charge carriers under a reverse bias applied by means of said confinement layers;

(b) means defining grooving at least partly through said waveguide core layer and for defining individual electro-optic waveguides, said individual electro-optic waveguides forming an array;

(c) a grooving medium contained in said electro-optic waveguides having a refractive index at least 1.5 less than said waveguide core layer refractive index, said means defining grooving and said medium comprising a means for inhibiting optical coupling between adjacent electro-optic waveguides;

(d) means arranging said electro-optic waveguides for inhibiting output of unwanted spatial modes;

(e) a common analog voltage input;

(f) a signal processing means for providing a digital output corresponding to analogue input voltage;

(g) a detector array, said detector array comprising detectors disposed along a path traversed by an electro-optic waveguide output in response to voltage input variation, and the detector array is connected to said signal processing means; and

(h) the number of electro-optic waveguides is m, each of said waveguides include respective bias electrodes, each bias electrodes having a length nL, where n=1 to m and denotes the nth waveguide and electrode, and L is the length of a first electrode, the electrodes are connected to said common analog voltage input, said electro-optic waveguides and said bias electrodes comprising a means for providing said electro-optic waveguide outputs which are focussed together at said detector array.

17. A device according to claim 16 wherein said signal processing means includes comparing means for comparing each detector output signal with a reference signal level.

18. A device according to claim 16 wherein said electro-optic waveguides each further include respective second bias electrodes, said second bias electrodes comprising a means for producing a common electro-optic waveguide output focus under conditions of zero analogue input voltage.

19. A device according to claim 16 wherein said detector array is two dimensional and coded to provide output binary words.

20. A device according to claim 19 wherein said detector array has a Gray-code format.

21. An electro-optic waveguide device of multilayer construction including an array of electrically biasable waveguides of electro-refractive material, said device comprising:

(a) a waveguide core layer having a refractive index and two light confinement layers sandwiching said core layer therebetween, each of said confinement layers having a refractive index lower than said core layer refractive index, said waveguide core layer comprises at least part of a diode structure and said diode structure depletable of charge carriers under a reverse bias applied by means of said confinement layers, wherein said waveguide core layer is comprised of an electro-absorbing material at a light source wavelength;

(b) means defining grooving at least partly through said waveguide core layer and for defining individual electro-optic waveguides, said individual electro-optic waveguides forming an array;

(c) a grooving medium contained in said electro-optic waveguides having a refractive index at least 1.5 less than said waveguide core layer refractive index, said means defining grooving and said medium comprising a means for inhibiting optical coupling between adjacent electro-optic waveguides;

(d) means arranging said electro-optic waveguides for inhibiting output of unwanted spatial modes;

(e) detecting means for providing an analog output signal in accordance with a binary input signal; and

(f) electrical biasing means for biasing each electro-optic waveguide corresponding to a respective binary digit, said electro-optic waveguide output intensities are weighted to form a binary doubling progression accross the waveguide array, the waveguides are each arranged to be one of opaque and transmitting in accordance to their respective bias voltages being one of two values corresponding to a binary digit, and said electro-optic waveguide output intensities are detected and summed by said detecting means where the detecting means output is an analog output signal in accordance with the binary digits to which the electrode voltages correspond.

22. An electro-optic waveguide device of the kind incorporating an array of electrically biasable waveguides of electro-optic material, and wherein:

(a) the device is of multilayer construction, and includes a waveguide core layer sandwiched between two light confinement layers of lower refractive index,

(b) the waveguide core layer is part of a diode structure and is depletable of charge carriers under reverse bias applied via the confinement layers,

(c) grooving extends at least partly through the waveguide core layer to define individual waveguides of the array, the grooving containing a medium with refractive index at least 1.5 less than that of the waveguide core layer to inhibit optical coupling between adjacent waveguides,

(d) the waveguides are arranged to inhibit output of unwanted spatical modes, and

(e) the waveguides have respective electrodes of which adjacent pairs are connected together via respective radio frequency (RF) inductors forming a chain having an RF input, the waveguides have respective outputs imaged on to respective detectors, and a pulsed laser is arranged to illuminate the waveguides with light having a wavelength for which the waveguide material is electro-absorbing as appropriate to sample RF signals on the inductor chain in terms of signals received by the detectors.

23. An electro-optic waveguide device of the kind incorporating an array of electrically biasable waveguides of electro-optic material, and wherein:

(a) the device is of multilayer construction, and includes a waveguide core layer sandwiched between two light confinement layers of lower refractive index,

(b) the waveguide core layer is part of a diode structure and is depletable of charge carriers under reverse bias applied via the confinement layers,

(c) grooving extends at least partly through the waveguide core layer to define individual waveguides of the array, the grooving containing a medium with refractive index at least 1.5 less than that of the wave guide core layer to inhibit optical coupling between adjacent waveguides,

(d) the waveguides are arranged to inhibit output of unwanted spatial modes, and

(e) each waveguide has parabolic input and output regions.

24. An electro-optic waveguide device of the kind incorporating an array of electrically biasable waveguides of electro-refractive material, and wherein:

(a) the device is of multilayer construction, and includes a waveguide corer layer sandwiched between two light confinement layers of lower refractive index,

(b) the waveguide core layer is part of a diode structure and is depletable of charge carriers under reverse bias applied via the confinement layers,

(c) grooving extends at least partly through the waveguide core layer to define individual waveguides of the array, the grooving containing a medium with refractive index at least 1.5 less than that of the waveguide core layer and providing substantial optical isolation between adjacent waveguides,

(d) the waveguides are arranged to inhibit output of unwanted spatial modes,

(e) the waveguides are biasable to produce radiation outputs which interfere to generate a far field diffraction pattern with a steerable main lobe, and

(f) the device includes receiving means disposed to receive the steered main lobe.

25. An electro-optic waveguide device of the kind incorporating an array of electrically biasable waveguides of electro-refractive material, and wherein:

(a) the device is of multilayer construction, and includes a waveguide core layer sandwiched between two light confinement layers of lower refractive index,

(b) the waveguides core layer is part of a diode structure and is depletable of charge carriers under reverse bias applied via the confinement layers,

(c) grooving extends at least partly through the waveguide core layer to define individual waveguides of the array, the grooving containing a medium with refractive index at least 1.5 less than that of the waveguide core layer to inhibit optical coupling between adjacent waveguides,

(d) the waveguides are arranged to inhibit output of unwanted spatial modes,

(e) a respective biasing means is associated with each waveguide and provides means for controlling the phase of radiation output from that waveguide, and

(f) the waveguides and biasing means are in combination arranged to provide for waveguide radiation outputs to interfere and produce at least one curved output radiation wavefront arising from non-linear output phase variation across a plurality of adjacent waveguides forming at least part of the array.

26. An electro-optic waveguide device of the kind incorporating an array of electrically biasable waveguides of electro-optic material arranged to receive light from a common source and form a common diffraction pattern, and including:

(a) waveguide bias electrodes of length nL, where n=1 to m indicating waveguide number in the array and L is the length of a first electrode,

(b) connections from the electrodes to a common analogue voltage input,

(c) a detector array which is two-dimensional and disposed along a path executed by a waveguide output beam in response to input analogue voltage variation,

(d) comparing means for comparing detector outputs with a reference signal derived from the light source and indicating device operative state,

(e) a respective second bias electrode for each waveguide, the second bias electrodes being independently biasable to combine the waveguide outputs on a single detector at zero input analogue voltage, and

(f) detector array output means which are coded to provide a digital signal corresponding to electrode analogue input voltage.

27. An electro-optic waveguide device of the kind comprising an array of electrically biasable waveguides of electro-optic material arranged to receive light from a common source and form a common diffraction pattern with a main lobe, and including:

(a) waveguide bias electrodes of length nL, where n=1 to m indicating waveguide number in the array and L is the length of a first electrode,

(b) connections from the electrodes to a common analogue voltage input,

(c) a detector array disposed along a path executed by the main lobe in response to input analogue voltage variation,

(d) waveguide biasing means arranged to provide for the main lobe to be directed to a prearranged detector array location under zero analogue input voltage conditions, and

(e) detector array output coding means arranged to provide a digital signal corresponding to electrode analogue input voltage.

28. An electro-optic waveguide device including:

(a) an array of electrically biasable waveguides of electro-absorbing material arranged to receive and transmit light from a common source,

(b) separating means disposed between the waveguides to provide optical isolation therebetween,

(c) a respective bias electrode means for each waveguide, the electrode means being arranged to render the associated waveguide opaque or transmitting in response respectively to two electrode voltages,

(d) means for weighting the waveguide output intensities selectively in accordance with a binary doubling scheme so that each waveguide is associated with a respective binary digit significance, and

(e) means for detecting and summing weighted output intensities derived from the waveguides, the detecting means being arranged to provide an analogue output voltage corresponding to digital to analogue conversion of voltages applied to the waveguide bias electrode means.

29. An electro-optic waveguide device including:

(a) an array of electrically biasable waveguides of electro-absorbing material each arranged to receive and transmit light from a pulsed laser,

(b) separating means disposed between the waveguides to provide optical isolation therebetween,

(c) a respective bias electrode for each waveguide, the electrode being arranged to vary the associated waveguide transmission characteristics in response to applied electrode voltage,

(d) a respective inductor connecting each adjacent pair of bias electrodes, the inductors collectively forming a chain connected to a radio-frequency (RF) signal input,

(e) a respective detector arranged to detect light transmitted by each waveguide, the detectors being collectively arranged to provide sampling of an RF signal portion distributed over the inductor chain during transmission of a laser pulse by the waveguides.