Power scalable optical systems for generating, transporting, and delivering high power, high quality, laser beams

• US 20030063884A1
• Filed: 04/05/2002
• Published: 04/03/2003
• Est. Priority Date: 01/04/2001
• Status: Active Grant

• Current Assignee: Lockheed Martin Coherent Technologies, Inc. (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Coherent Technologies, Inc. (Martin Marietta Corporation)
• Inventors: Pelouch, Wayne S., McKinnie, Iain, Smith, Duane D., Unternahrer, Josef, Prasad, Narasimha S., Koroshetz, John
• Granted Patent: US 7,042,631 B2
• Time in Patent Office: Days
• US Class Current: 385/129
• CPC Class Codes: G02B 6/032 with non solid core or cladding G02B6/02295 takes precedence
• CPC Class Codes: G02B 6/2813 based on multimode interference effect, i.e. self-imaging
• CPC Class Codes: H01S 3/042 for solid state lasers H01S3/0401 takes precedence
• CPC Class Codes: H01S 3/063 Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength waveguide gas lasers H01S3/0315
• CPC Class Codes: H01S 3/08095 Zig-zag travelling beam through the active medium
• CPC Class Codes: H01S 3/094057 by tapered duct or homogenized light pipe, e.g. for concentrating pump light
• CPC Class Codes: H01S 3/0941 of a laser diode
• CPC Class Codes: H01S 3/1643 YAG
• CPC Class Codes: H01S 3/2333 Double-pass amplifiers
• CPC Class Codes: H01S 3/2383 Parallel arrangements
• CPC Class Codes: H01S 5/10 Construction or shape of the optical resonator , e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region H01S5/20 takes precedence
• CPC Class Codes: H01S 5/50 Amplifier structures not provided for in groups H01S5/02 - H01S5/30

Abstract

Power scalable, rectangular, multi-mode, self-imaging, waveguide technologies are used with various combination of large aperture configurations, 20, 50, 80, 322, 324, 326, 328, 330, 332, 334, 336, 338, Gaussian 360 and super-Gaussian 350 beam profiles, thermal management configurations 100, flared 240 and tapered 161 waveguide shapes, axial or zig-zag light propagation paths, diffractive wall couplers 304, 306, 308, 310, 312, 314, 316, 318, 320 and phase controller 200, flexibility 210, phased arrays 450, 490, beam combiners 530, 530′, and separators 344, 430, and other features to generate, transport, and deliver high power laser beams.

Claims

1. A power scalable optical system for generating, transporting, and delivering high power laser beams, comprising:

means for producing a high power, super-Gaussian laser beam; and

a multi-mode, self-imaging waveguide coupled optically to receive and transmit said high power, super-Gaussian laser beam to at least one output aperture that is positioned in a re-imaging plane in the waveguide.

2. The power scalable optical system of claim 1, wherein said means for producing a high power, super-Gaussian laser beam includes an amplifier for a laser beam that has a wavelength (λ

), comprising;

a multi-mode, self-imaging waveguide having a core comprising a gain or mixing medium with an index of refraction (n) and a core length extending between a core entrance face and a core exit face, said core also having a rectangular cross-section that provides a waveguide width (a), which is large enough to support and propagate multiple modes of the laser beam and a waveguide self-imaging period (WSIP) defined as a distance in the multi-mode waveguide in which a profile or image of the laser beam is periodically re-imaged, wherein WSIP=4na²/λ

in general for the laser beam propagating through the core and WSIP=na²/λ

when the laser beam is symmetric with respect to the center of the waveguide, and wherein said core is such that the laser beam propagating through the core from the core entrance face to the core exit face has an optical path length with a numerical aperture and an exit face that is a non-zero integer multiple of the waveguide self-imaging period (WISP);

means for modifying phase and/or amplitude profile of a beam to provide an input laser beam with a super-Gaussian profile and for focusing the input laser beam at the core entrance face within the numerical aperture of the core entrance face to propagate the laser beam into and through the waveguide to the exit face; and

a pump light source coupled into the waveguide core medium to propagate pump light energy into the core medium to be extracted by the laser beam.

3. The amplifier of claim 2, including a reflector capable of reflecting the laser beam positioned to reflect the laser beam back through the waveguide core.

4. The amplifier of claim 3, wherein the reflector is positioned at the exit face.

5. The amplifier of claim 3, wherein the reflector is positioned outside the waveguide at a distance from the exit face.

6. The amplifier of claim 5, wherein the reflector is shaped to re-focus the reflected laser beam onto the exit face for propagation back through the waveguide core.

7. The amplifier of claim 5, including an optical imaging system between the exit face and the reflector that is capable of re-imaging the reflected laser beam on the exit face for propagation back through the waveguide core.

8. The amplifier of claim 3, including an extraction optical coupling system capable of coupling the reflected laser beam out of the entrance face of the waveguide and separating the reflected laser beam from the pre-amplified laser beam.

9. The amplifier of claim 8, wherein the extraction optical coupling system includes a polarizing beam splitter positioned in the pre-amplified beam and a ¼

-λ

) birefringent retarder positioned between the polarizing beam splitter and the entrance face of the waveguide core.

10. The amplifier of claim 3, wherein the pump light source is coupled into the waveguide core medium through the exit face.

11. The amplifier of claim 10, wherein the reflector is transparent to the pump light.

12. The amplifier of claim 2, wherein the pump light source is coupled into the waveguide core medium through a lateral side of the waveguide core medium.

13. The amplifier of claim 12, wherein the pump light source is a laser diode.

14. The amplifier of claim 13, wherein the pump light source produces pump light with a wavelength that is smaller than the wavelength λ

of the laser beam.

15. The amplifier of claim 12, including multiple pump light sources coupled into lateral sides of the waveguide core medium.

16. The amplifier of claim 2, wherein the gain medium is a semiconductor material.

17. The amplifier of claim 16, wherein the semiconductor medium comprises AlGaAs.

18. The amplifier of claim 2, wherein the gain medium is a ion-doped, glassy material.

19. The amplifier of claim 2, wherein the gain medium is a crystalline material.

20. The amplifier of claim 2, wherein the gain medium is a refractory material.

21. The amplifier of claim 2, wherein the gain medium comprises sapphire.

22. The amplifier of claim 2, wherein the gain medium comprises at least one oxide.

23. The amplifier of claim 2, wherein the gain medium comprises at least one germanite.

24. The amplifier of claim 2, wherein the gain medium comprises at least one fluoride.

25. The amplifier of claim 2, wherein the gain medium comprises at least one chloride.

26. The amplifier of claim 2, wherein the gain medium comprises at least one chalcogenide.

27. The amplifier of claim 2, wherein the gain medium comprises at least one apatite.

28. The amplifier of claim 2, wherein the gain medium comprises doped YAG.

29. The amplifier of claim 28, wherein the gain medium comprises Yb:

YAG.

30. The amplifier of claim 2, wherein the gain medium comprises Nd dopant.

31. The amplifier of claim 2, wherein the gain medium comprises a liquid.

32. The amplifier of claim 31, wherein the gain medium comprises an optically nonlinear liquid.

33. The amplifier of claim 31, wherein the gain medium comprises CS₂.

34. The amplifier of claim 2, wherein the core is rectangular and is clad with a cladding material that has a lower index of refraction than the core.

35. The amplifier of claim 2, wherein the core is rectangular, has no cladding, but has an index of refraction that is sufficiently greater than a surrounding atmosphere to confine the light beam in the core.

36. The amplifier of claim 35, wherein the core comprises Nd-doped, phosphate glass.

37. The amplifier of claim 34, including a heat sink positioned adjacent and in contact with the cladding material.

38. The amplifier of claim 34, wherein the cladding material has at least one flat side and the heat sink is positioned in contact with the flat side.

39. The amplifier of claim 38, wherein the pump light source also has at least one flat side that is positioned in thermally conductive contact with a flat side of the sink.

40. The amplifier of claim 39, wherein the heat sink has a uniform thickness.

41. The amplifier of claim 39, wherein the heat sink has a varying thickness.

42. The amplifier of claim 35, including an intervening heat conductor layer on a surface of the core and a heat sink positioned on the intervening heat conductor layer.

43. The amplifier of claim 40, wherein the intervening layer comprises a fluoropolymer material.

44. The amplifier of claim 40, wherein the intervening layer comprises a silico-oxide material.

45. The power scalable optical system of claim 1, wherein said means for producing a high power, super-Gaussian laser beam includes a laser resonator for producing a laser beam, comprising:

a multi-mode, self-imaging waveguide positioned in an optical resonator cavity and having a core medium, which, when excited, emits light with a wavelength (λ

), said core medium having a core length extending between a first core face and a second core face and also having an index of refraction (n) and a rectangular cross-section that provides a waveguide width (a), which is large enough to support and propagate multiple modes of a laser beam and a waveguide self-imaging period (WSIP) defined as a distance in the multi-mode waveguide in which a laser beam profile or image is periodically re-imaged, wherein WSIP=4na²/λ

in general for the laser beam propagating through the core and WSIP=na²/λ

when the laser beam is perfectly symmetric with respect to the center of the waveguide, and wherein said core length is such that the laser beam propagating through the core from the first face to the second face has an optical path length that is a non-zero integer multiple of the waveguide self-imaging period (WSIP); and

means adjacent the first face and/or the second face for conditioning the laser beam to have a super-Gaussian profile.

46. The laser resonator of claim 45, including a pump light source coupled optically to the waveguide core medium to propagate pump light energy into the core medium at a wavelength that optically excites the core medium to emit the λ

wavelength light.

47. The laser resonator of claim 45, wherein the core medium is a optoelectronic semiconductor material and the laser resonator includes electrical contacts positioned adjacent the core medium in a manner that facilitates application of an electric current to excite the semiconductor material to produce the laser light.

48. The laser resonator of claim 45, wherein either the first core face or the second core face includes a rectangular aperture for the laser light to exit and enter the core medium, and wherein the optical resonator cavity includes a reflective surface positioned a distance apart from the core medium and in alignment with the rectangular aperture to reflect laser light that emanates from the core medium back into the rectangular aperture to reflect laser light that emanates from the core medium back into the rectangular aperture with a super-Gaussian profile of a selected order at the rectangular aperture.

49. The laser resonator of claim 46, wherein the selected order is a lower order.

50. The laser resonator of claim 49, wherein the reflective surface is curved to focus the reflected laser light on the rectangular aperture with the lower order super-Gaussian profile.

51. The laser resonator of claim 45, wherein the means for conditioning the laser beam to have a super-Gaussian profile includes a phase modification plate.

52. The laser resonator of claim 45, wherein the means for conditioning the laser beam to have a super-Gaussian profile includes a phase modification plate.

53. The laser resonator of claim 45, wherein the means for conditioning the laser beam to have a super-Gaussian profile includes an amplitude modification plate.

54. The laser resonator of claim 48, wherein the reflective surface is fully reflective.

55. The laser resonator of claim 48, wherein the reflective surface is partially reflective.

56. The laser resonator of claim 48, wherein the reflective surface is a first reflective surface and the optical resonator cavity includes a second reflective surface with the core medium positioned between the first reflective surface and the second reflective surface.

57. The laser resonator of claim 56, wherein the second reflective surface is fully reflective.

58. The laser resonator of claim 56, wherein the second reflective surface is partially reflective.

59. The laser resonator of claim 56, wherein the second reflective surface is positioned at either the first core face or the second core face.

60. The laser resonator of claim 45, wherein the self-imaging waveguide is rectangular in cross-section.

61. The laser resonator of claim 60, wherein the rectangular waveguide comprises:

a rectangular core medium with flat external surfaces;

cladding on the external surfaces, said cladding also having at least one flat external surface; and

a heat sink positioned in contact with the flat external surface of the cladding.

62. The amplifier of claim 2, including cladding material with an index of refraction less than the index of refraction of the core medium.

63. The amplifier of claim 62, wherein said cladding material is a first cladding material, and wherein the amplifier includes:

a second cladding material surrounding the first cladding material and having an index of refraction that is less than the index of refraction of the first cladding material; and

wherein the pump light source coupled optically to the core medium via an optical coupling to the first cladding material.

64. The amplifier of claim 62, wherein the core medium and the first cladding material comprise a longitudinally elongated, optical fiber.

65. The amplifier of claim 47, wherein the core medium, the first cladding material, and the second cladding material comprise a longitudinally elongated, optical fiber.

66. The amplifier of claim 64, wherein optical fiber has a circular cross-section.

114. The laser apparatus of claim 112, including a stacked array of laser diode pump light sources coupled optically to the waveguide.

136. The method of claim 135, including conditioning the input laser beam to have a lower order super-Gaussian profile.

67. An optical system for delivering a beam with a desires spatial profile to an application, comprising:

an elongated, twistable, and bendable, multi-mode, self-imaging, beam transport waveguide that has at least one inlet aperture and at least one outlet aperture spaced a distance of WSIP×

i from the inlet aperture; and

a laser amplifier with optical components that are capable of producing a laser beam with the desire spatial profile coupled to the inlet aperture of the beam transport waveguide.

68. The optical system of claim 67, including a plurality of outlet apertures distributed in different locations along the beam transport waveguide, wherein each outlet aperture is a distance of WSIP×

i from the inlet aperture, and where i is different for at least some of the outlet apertures.

69. The optical system of claim 68, including an addressable outlet coupler at each outlet aperture.

70. The optical system of claim 69, wherein the outlet coupler comprises a diffraction grating.

71. The optical system of claim 67, including a liquid crystal outlet coupler at the outlet aperture, said liquid crystal having a variable index of refraction that varies, in response to voltage changes across the liquid crystal, in a range between an index of refraction that confines all light in the waveguide and an index of refraction that couples at least some of the light out of the waveguide.

72. The optical system of claim 67, including an array of individually addressable, electric contacts adjacent the liquid crystal that can be addressed with different voltages to vary indices of refraction of a plurality of different portions of the liquid crystal, and which contacts are small enough and positioned closely enough together such that different portions of the liquid crystal can be actuated to change indices of refraction in a manner that functions as a grid to launch light coupled out of the waveguide in a desire direction.

73. The optical system of claim 71, including a second multi-mode, self-imaging, waveguide with at least one inlet aperture and at least one outlet aperture, wherein the inlet aperture of the second waveguide is positioned adjacent the outlet aperture of the first waveguide such that light coupled by the liquid crystal out of the waveguide is coupled into the second waveguide, and wherein the outlet aperture of the second waveguide is positioned at a distance equal to WSIP×

i from the inlet aperture of the second waveguide.

74. The optical system of claim 73, wherein the liquid crystal in the outlet aperture of the first waveguide is actuateable to couple out of the waveguide no more than ten percent of the light in the waveguide per ¼

-Talbot period.

75. The optical system of claim 74, wherein the second waveguide is elongated, twistable, and bendable and has a plurality of outlet apertures distributed in different locations along its length, and wherein each outlet aperture in the second waveguide is positioned at respective distances from the inlet aperture equal to WSIP×

i, where i is different for at least some of the outlet apertures in the second waveguide.

76. The optical system of claim 74, including a liquid crystal outlet coupler at the outlet aperture of the second waveguide, said liquid crystal having a variable index of refraction that varies, in response to voltage changes across the liquid crystal, in a range between an index of refraction that confines all light in the second waveguide and an index of refraction that couples at least some of the light out of the second waveguide.

77. The optical system of claim 67, including:

two outlet apertures positioned in a common plane, but on opposite sides of the beam transport waveguide and at a distance of WSIP×

i from the inlet aperture;

a first branch waveguide with a first branch inlet aperture and at least one first branch outlet aperture, said first branch waveguide being positioned so that the first branch inlet aperture is adjacent and coupled optically to one of the outlet apertures of the beam transport waveguide, and wherein the first branch outlet aperture is positioned at a distance of WSIP×

i from the first branch inlet aperture;

a second branch waveguide with a second branch inlet aperture and at least one second branch outlet aperture, said second branch waveguide being positioned so that the second branch inlet aperture is adjacent and coupled optically to the other one of the outlet apertures of the beam transport waveguide, and wherein the second branch outlet aperture is positioned at a distance of WSIP×

i from the second branch inlet aperture.

78. The optical system of claim 77, wherein i is not necessarily the same for each of the distances WSIP×

i.

79. The optical system of claim 78, including a first liquid crystal modulator positioned in one of the outlet apertures and a second liquid crystal modulator positioned the other one of the outlet apertures.

80. The optical system of claim 67, wherein the beam transport waveguide has a hollow core for high power beam transport without nonlinear thermally-induced optical distortions.

81. An amplifier system for producing a high power laser beam, comprising:

a multi-mode, self-imaging, waveguide having a core of solid gain or mixing medium with a rectangular cross-section, and cladding material that has a coefficient of thermal conduction, interior cladding surfaces abutting opposite, waveguiding surfaces of the rectangular core, and exterior cladding surfaces that are opposite the interior cladding surfaces;

a beam input coupling system capable of providing a desired spatial phase profile of the laser beam at an entrance aperture of the core to propagate the laser beam into waveguide;

a pump light source coupled into the waveguide core medium to propagate pump light energy into the core medium to be extracted by the laser beam;

a beam output coupling system capable of coupling an output beam from the core at a plane where the beam propagating in the core re-phases into the desired spatial phase profile; and

a heat sink positioned adjacent and in contact with an exterior surface of the cladding material, said heat sink.

82. The amplifier system of claim 81, wherein the heat sink has a coefficient of thermal conduction that is higher than the coefficient of thermal conduction of the cladding.

83. The amplifier system of claim 81, wherein the heat sink comprises a heat spreader, which has a coefficient of thermal conduction lower than the coefficient of thermal conduction of the cladding.

84. The amplifier system of claim 81, wherein at least one exterior surface of the cladding material is flat and wherein the heat sink has at least one flat surface that is positioned in contact with the flat exterior surface of the cladding.

85. The amplifier system of claim 84, wherein the core is a one-dimensional, self-imaging, waveguide core, and wherein the cladding abutting one of the waveguiding surfaces has a heat sink with a flat surface abutting a flat exterior surface of the cladding and the cladding abutting the opposite one of the waveguiding surfaces also has a heat sink with a flat surface abutting a flat exterior surface of the cladding so that heat flow through the core to the cladding is substantially one-dimensional.

86. The amplifier system of claim 84, wherein the heat sink is wider than the waveguide so that the flat surface of the heat sink extends laterally outward from the cladding, and wherein the pump light source includes at least one laser diode with a flat exterior side, said laser diode being positioned to couple light energy produced by the laser diode into a lateral side of the waveguide and with the flat exterior side of the laser diode in contact with the flat surface of the heat sink.

87. The amplifier system of claim 84, wherein the heat sink has a uniform thickness.

88. The amplifier system of claim 84, wherein the heat sink has a varying thickness for maintaining a desired temperature profile in the waveguide.

89. The amplifier system of claim 86, wherein the pump light source includes a plurality of laser diodes with flat sides mounted on the flat surface of the heat sink and distributed spatially along opposite lateral sides of the waveguide in positions to couple light from the laser diodes into lateral sides of the waveguide.

90. The amplifier system of claim 81, wherein the heat sink is passive.

91. The amplifier system of claim 90, wherein the heat sink comprises carbon-carbon composite.

92. The amplifier system of claim 81, wherein the heat sink is active.

93. The amplifier system of claim 92, wherein the heat sink comprises a copper micro/mini channel fluid heat sink.

94. The amplifier system of claim 81, wherein the core medium has a coefficient of thermal expansion and the cladding material has a coefficient of thermal expansion that is not more than twenty percent less than the coefficient of thermal expansion of the core material.

95. The amplifier system of claim 94, wherein the cladding material is capable of bonding to the core material.

96. The amplifier system of claim 95, wherein the core material comprises YAG and the cladding material comprises sapphire (Al₂O₃).

97. The amplifier system of claim 95, wherein the cladding material has a thickness of no more than 1 mm.

98. The amplifier system of claim 95, wherein difference between heat conductivity of the core material and heat conductivity of the cladding material is no more than twenty-five percent of the heat conductivity of the cladding material.

99. Laser amplifier apparatus, comprising:

a multi-mode, rectangular, self-imaging, waveguide comprising a core of optical gain or mixing medium with a rectangular cross-section, opposed top and bottom surfaces, and opposed left and right lateral surfaces, reflectors adjacent the left and right lateral surfaces, an inlet aperture, and an outlet aperture;

a pump light source coupled optically into the core;

an optical system positioned to couple an input laser beam with a desired spatial profile to the input aperture at an angle that propagates the laser beam to reflect off the reflectors in a zig-zag path in the core medium to the outlet aperture positioned in a re-imaging plane where the beam re-phases into the desired spatial profile.

100. The laser amplifier apparatus of claim 99, wherein the zig-zag path from the inlet aperture to the outlet aperture has a length equal to WSIP×

i.

101. The laser amplifier apparatus of claim 99, wherein the input beam has a first wavelength and the pump light has a second wavelength, the reflectors are dichroic mirrors that reflect light having the first wavelength and transmit light having the second wavelength, and the pump light source is positioned adjacent the left and right lateral surfaces to direct pump light through the dichroic mirrors into the core medium.

102. The laser amplifier apparatus of claim 99, wherein the core has a first end face and a second end face at respective opposed ends of the core, the inlet aperture and the outlet aperture are both at the first end face, and the optical system also include a reflective component adjacent the second end face positioned to redirect the beam, emerging from the second face after propagating through a first leg of the zig-zag path, back into the second face to propagate through a second leg of the zig-zag path to the outlet aperture.

103. The laser amplifier apparatus of claim 102, wherein the reflective components adjacent the second end face is positioned to redirect the beam back into the second face in an orientation that causes the second leg of the zig-zag path to propagate through some portions of the core that are not occupied by the first leg of the zig-zag path.

104. The laser amplifier apparatus of claim 100, wherein, the outlet apparatus of claim 100, wherein, the outlet aperture is the same as the inlet aperture and at least one lateral edge tapered toward a longitudinal axis of the core medium so that angles of incidence of the laser beam to the reflectors become smaller and density of the zig-zag path becomes greater as the beam propagates through the core medium until it reaches a terminal path segment at which the beam reverse propagates back through the zig-zag path to the inlet and outlet aperture.

105. The laser amplifier apparatus of claim 101, wherein the tapered lateral edge is straight.

106. The laser amplifier apparatus of claim 101, wherein the tapered lateral edge is curved.

107. The laser amplifier apparatus of claim 100, the pump light source is coupled optically into a portion of the core where the optical path has a higher density than another portion of the core.

108. Laser amplifier apparatus, comprising:

a multi-mode, one-dimensional, rectangular, self-imaging, waveguide including a core with a length equal to WSIP×

i and which is flared outwardly in a non-imaging, transverse, direction so that the core has increasing larger rectangular cross-sections from an inlet face at one end of the core to an outlet face at the opposite end; and

a pump light source coupled optically to the core.

109. The laser amplifier apparatus of claim 108, including cladding on waveguiding surfaces of the core.

110. The laser amplifier apparatus of claim 108, wherein the pump light source includes a plurality of laser diodes distributed along at least one lateral side of the waveguide.

111. The laser amplifier apparatus of claim 110, wherein laser diodes closer to the outlet face emit more power than laser diodes that are closer to the inlet face.

112. Laser apparatus, comprising:

a multi-mode, rectangular, self-imaging, waveguide, which has a core comprising a solid gain medium laminated between two sheets of cladding with exterior surfaces, said waveguide being sandwiched between two heat sinks, each of which has a heat sink surface that interfaces in contacting relation with one of the exterior surfaces of the cladding and that extends outwardly beyond the cladding to form a pump mounting surface;

at least one laser diode pump light source mounted in thermally conductive relation to the heat sink surfaces and in a position to couple pump light into the core; and

an optical system configured and positioned to direct a beam into the core of the waveguide with a desired spatial profile and to couple the beam out of the core after the beam has extracted pump energy from the core and at a re-imaging plane where, after having separated into multiple modes of propagation through the core, the beam re-phases into the desired spatial profile.

113. The laser apparatus of claim 112, wherein the waveguide is a one-dimensional, rectangular, self-imaging, waveguide.

115. The laser apparatus of claim 112, wherein the heat sink comprises carbon-carbon composite.

116. The high power laser apparatus of claim 112, wherein the heat sink comprises a copper micro/mini channel fluid heat sink.

117. The Laser apparatus, comprising:

a multi-mode, rectangular, self-imaging, waveguide, which has a core comprising an unclad, solid gain medium and at least one flat side;

a heat sink with at least one flat side positioned in thermal conductive relation to the flat side of the core;

at least one laser diode pump light source mounted in position to couple pump light into the core; and

an optical system configured and positioned to direct a beam into the core of the waveguide with a desired spatial profile and to couple the beam out of the core after the beam has extracted pump energy from the core and at a re-imaging plane, where, after having separated into multiple modes of propagation through the core, the beam re-phases into the desired spatial profile.

118. The laser apparatus of claim 117, including an intervening, heat conductive, material positioned between the core and the heat sink, said intervening material having an index of refraction that is low enough to not interfere with waveguiding of light in the core.

119. An optical beam combiner, comprising:

a first multi-mode, rectangular, self-imaging, input waveguide that has a first input waveguide inlet aperture and a first input waveguide outlet aperture, wherein the first input waveguide outlet aperture is positioned a distance of WSIP×

i from the first input waveguide inlet aperture;

a second multi-mode, rectangular, self-imaging, input waveguide that has a second input waveguide inlet aperture and a second input waveguide outlet aperture, wherein the second input waveguide outlet aperture is positioned adjacent and in a common plane with the first input waveguide outlet aperture and at a distance of WSIP×

i from the second input waveguide inlet aperture;

a multi-mode, rectangular, self-imaging combiner waveguide that has a combiner waveguide inlet aperture sized and shaped to match a composite of the first input waveguide outlet aperture and the second input waveguide outlet aperture positioned in the common plane, said combiner waveguide inlet aperture also being positioned in the common plane and coupled optically to receive light from both the first and second inlet waveguide outlet apertures, and said combiner waveguide also having a combiner waveguide outlet aperture that is positioned at a self-imaging plane of the combiner waveguide.

120. The optical beam combiner of claim 119, wherein the combiner has a constant size rectangular cross-section from the combiner waveguide inlet aperture to the combiner waveguide outlet aperture.

121. The optical beam combiner of claim 119, wherein the combiner waveguide is tapered to have a decreasing size rectangular cross-section from the combiner waveguide inlet aperture to the combiner waveguide outlet aperture.

122. The optical beam combiner of claim 121, wherein the combiner waveguide is adiabatically tapered.

123. A laser beam transport system, comprising:

a plurality of multi-mode, rectangular, self-imaging, waveguides stacked together in an array, wherein all of the waveguides in the array are of equal cross-sectional shape and size and of equal length and have input apertures all in a common input aperture plane and output apertures all in a common output aperture plane, said length between the input aperture plane and the output aperture plane being equal to WSIP×

i.

124. The laser beam transport system of claim 123, including means for producing a plurality of phase-matched laser beams that have a common spatial profile and for coupling each of the plurality of laser beams into respective inlet apertures of the waveguides in the array so that the laser beams propagate in multiple modes through the respective waveguides in the array and re-phase at the respective outlet apertures to combine together in a composite laser beam with the common spatial profile.

125. The laser beam transport system of claim 123, including:

a transmitter array that produces a plurality of beams in an array, each of said beams being an integral part of a composite image, and optically couples such beams into respective ones of the waveguides; and

a detector array with individual photo detector elements that correspond to respective ones of the waveguides positioned and aligned to detect the respective beams propagated through the waveguides to the outlet apertures.

126. A laser beam synthesizer, comprising:

a plurality of multi-mode, rectangular, self-imaging waveguides, each of which has an inlet aperture and at least one outlet aperture positioned at a distance of WSIP×

i from the input aperture;

means for producing a plurality of phase-matched beams with a common spatial profile and for coupling such beams into the inlet apertures of respective ones of said waveguides; and

a beam director positioned at each of the outlet apertures, the beam director at each of the outlet apertures being set to direct all of the beams to a common point.

127. The laser beam synthesizer of claim 126, wherein the beam directors includes an electrically addressable, diffractive coupler.

128. A method of providing a high power, diffraction limited, laser beam to a desired application, comprising:

producing a high power laser beam with a spatial profile;

coupling said beam into an input aperture of an elongated, multi-mode, self-imaging, waveguide that extends to an output aperture positioned both at a desired point of delivery for the beam and at a self-imaging plane where the beam re-phases into the desire spatial profile; and

coupling said beam out of said output aperture for the desired application.

129. The method of claim 128 including producing the high power laser beam with a super-Gaussian profile.

130. The method of claim 129, including producing the high power laser beam with a super-Gaussian profile by:

conditioning an input laser beam to have a super-Gaussian profile; and

coupling the conditioned beam with its super-Gaussian profile into a core entrance face of a laser amplifier comprising a multi-mode, self-imaging waveguide having a core comprising a gain or mixing medium with a core length extending between the core entrance face and a core exit face, which is positioned in a self-imaging plane where the input laser beam, after separating into multiple modes for propagation through the core, re-phases into the super-Gaussian profile;

pumping the gain or mixing medium of the core with additional light energy; and

extracting such additional light energy from the gain or mixing medium with the input beam as it propagates in multiple modes through the core so that said input beam re-phases as an output beam at said exit face with the super-Gaussian profile and the additional energy extracted from the gain or mixing medium.

131. The method of claim 130, including in-coupling a free space spherical and/or plane wavefront into a wall coupling of a rectangular, multi-mode, self-imaging, waveguide.

132. The method of claim 130, including pumping and extracting sufficient light energy so that the re-phased, super-Gaussian profile, beam at said exit face is a high power beam.

133. The method of claim 132, including dissipating enough heat from the core to prevent optical distortions in the beam from thermal gradients in the core.

134. The method of claim 133, including dissipating heat from the core by placing at least one fiat side of the waveguide in contact with a flat surface of a heat sink.

135. The method of claim 130, including conditioning the input laser beam to have a super-Gaussian profile by modifying phases and/or amplitudes across the beam to a desired super-Gaussian order.

137. The method of claim 130, wherein the beam is Gaussian.

138. The method of claim 130, including propagating the beam in a zig-zag path through the core.

139. The method of claim 138, including propagating the beam a second time through the core in a second zig-zag path.

140. The method of claim 128, including coupling said beam out o said output aperture with a diffraction grating.

141. The method of claim 128, including coupling said beam out of said output aperture by actuating a liquid crystal material positioned at the aperture to increase index of refraction of the liquid crystal enough to disable waveguiding effect of the aperture to a sufficient extent to outcouple a desire amount of the light beam from the waveguide.

142. The method of claim 141, including steering the outcoupled portion of the beam to propagate in a desired direction in relation to the output aperture by selectively actuating spaced-apart portions of the liquid crystal in a manner that creates an optical grating with a desired density to refract the outcoupled beam to the desired direction.

143. The method of claim 141, including capturing the outcoupled beam into second waveguide that has an input aperture positioned adjacent said liquid crystal material.

144. The method of claim 128, including extending the elongated, self-imaging waveguide to the point of delivery of the beam by twisting and bending the elongated, self-imaging, waveguide a sufficient amount to avoid any adjacent obstacles, but not so much as to cause optical distortion of the desired phase and amplitude profile at the output aperture.

145. The method of claim 128, including controlling phase of the beam as the beam propagates in the waveguide by positioning a diffractive material in a wall of the waveguide and applying a voltage across the diffractive material in a manner that changes index of refraction of the diffractive material to an extent needed to modify phase of the propagating beam to a desire phase.

146. The method of claim 145, wherein the diffractive material is liquid crystal.

147. The method of claim 128 including controlling wavelength of the beam as the beam propagates in the waveguide by positioning a diffractive material in a wall of the waveguide and applying a voltage across the diffractive material in a manner that changes index of refraction of the diffractive material to an extent needed to couple light of undesired wavelengths out of the waveguide through the diffractive material.

148. The method of claim 147, wherein the diffractive material is liquid crystal.

149. The method of claim 128, including controlling phase of the beam propagating in the waveguide by squeezing the waveguide to deform the waveguide a sufficient amount to shift the phase of the beam.

150. The method of claim 128, including splitting the beam by:

positioning two outlet apertures in a common plane on opposite waveguiding sides of the waveguide and at a distance of WSIP×

i from the inlet aperture;

positioning a multi-mode, rectangular, self-imaging, first branch waveguide, which has a first branch inlet aperture and a first branch outlet aperture spaces from each other by a distance of WSIP×

i, adjacent one of the two outlet apertures of the waveguide and coupling a first portion of the beam from said one of the two outlet apertures into the first branch inlet aperture; and

positioning a multi-mode, rectangular, self-imaging, second branch waveguide, which has a second branch inlet aperture and a second branch outlet aperture spaced from each other by a distance of WSIP×

i, adjacent the other one of the two outlet apertures of the waveguide and coupling a second portion of the beam from said some of the two outlet apertures into the second branch inlet aperture.

151. The method of claim 150, including:

coupling said first portion of the beam out of said first branch outlet; and

coupling said second portion of the beam out of said second branch outlet.

152. The method of claim 150, including:

positioning a diffractive window in each of the two outlets of the waveguide; and

actuating the diffractive windows to couple desired amounts of light out of the waveguide in the first portion of the beam and in the second portion of the beam.

153. The method of claim 152, wherein the diffractive window comprises liquid crystal.

154. The method of claim 153, including actuating the respective liquid crystal windows by varying voltages across them.

155. A method of delivering a high power, composite beam with a desire spatial profile to an application, comprising:

assembling a plurality of multi-mode, rectangular, self-imaging, waveguides of equal cross-sectional dimensions and of equal length between respective inlet and outlet apertures of the waveguides into an array with the outlet apertures of all of the waveguides in a common plane;

producing a plurality of high power laser beams that are phase-matched to each other and that have the desired spatial profile;

coupling the plurality of laser beams into respective input apertures of the plurality of waveguides so that the laser beams propagate through separate waveguides to the outlet apertures in the common plane; and

coupling the laser beams out of the waveguides in a composite high power laser beam that has the desired spatial profile.

156. The method of claim 155, including producing the high power laser beams with a super-Gaussian spatial profile.

157. The method of claim 156, including producing the high power laser beams with a low order super-Gaussian spatial profile.

158. A method of transporting an image, comprising:

producing a plurality of phase-matched laser beams each of which comprises an integral portion of a composite image; and

coupling each of the beams into a respective one of an array of rectangular, multi-mode, self-imaging waveguides and maintaining respective positions of the waveguides in relation to each other at respective outlet apertures of the waveguides in a common outlet plane.

159. The method of claim 158, including coupling each of the laser beams from the respective outlet apertures to a photodetector array.

160. A method of delivering a synthesized, high power, laser beam with a desired spatial profile, comprising:

producing a plurality of phase-matched, high power laser beams with the desired spatial profile;

coupling the laser beams into input apertures of respective ones of a plurality of elongated, multi-mode, rectangular, self-imaging, waveguides, each of which waveguides has at least one outlet aperture spaced at a distance of WSIP×

i from the inlet aperture of such waveguide; and

coupling the laser beams out of said outlet apertures and directing them to a common point.