Configuration of and method for optical beam shaping of diode laser bars

• US 6,700,709 B1
• Filed: 03/01/2002
• Issued: 03/02/2004
• Est. Priority Date: 03/01/2002
• Status: Expired due to Fees

• Current Assignee: Boston Laser, Inc.
• Original Assignee: Boston Laser, Inc.
• Inventors: Fermann, Martin E.
• Primary Examiner(s): MACK, RICKY LEVERN
• Application Number:
  US10/085,620
• Time in Patent Office: 732 Days
• Field of Search: 359/618, 359/641, 385/33, 385/37, 372/50
• US Class Current: 359/641
• CPC Class Codes: G02B 19/0014 at least one surface having optical power
• CPC Class Codes: G02B 19/0023 at least one surface having optical power
• CPC Class Codes: G02B 19/0057 in the form of a laser diode array, e.g. laser diode bar semiconductor laser arrays with beam combining arrangement H01S5/4012
• CPC Class Codes: G02B 27/09 Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for adapting the beam shape of a laser diode G02B19/0052; adapting the beam shape of an LED G02B19/0061; coupling into light guides using intermediate optical elements G02B6/4204; beam shaping specially adapted for lasers H01S3/005
• CPC Class Codes: G02B 27/0961 Lens arrays lens arrays per se G02B3/0006
• CPC Class Codes: G02B 27/0966 Cylindrical lenses cylindrical lenses per se G02B3/06
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/4012 Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms
• CPC Class Codes: H01S 5/4025 Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence

Abstract

An optical beam shaping element is used to produce a beam of high brightness from a diode bar or a single emitter diode, allowing for efficient coupling of the beam into an optical fiber. An embodiment of the beam shaping element allows the construction of a quasi-monolithic or truly monolithic beam shaper incorporating both fast axis collimation as well as beam rotation. Additional slow axis collimation or collimation of the beam-rotated fast axes of the individual emitting elements of the diode bar is also possible in one quasi-monolithic or truly monolithic design. The beam rotation element comprises an array of beam-inverting planar grin lenses aligned with their axes of equal refractive index at an angle of ±45° with respect to the slow axes of the emitters. Alterative embodiments comprise beam rotation elements based on two planar grin lens arrays, arrays of uniaxial grin lenses, arrays of uniaxial focusing reflective optic or arrays of cylindrical Fresnel lenses. The beam shaping element can be used in conjunction with stacks of diode bars or alternatively optical beams of ultra-high power can be generated by combining multiple fiber coupled diode bars in a fiber bundle incorporating metallization and a heat sink.

Claims

1. An optical element for beam shaping of an optical laser beam emission of a diode laser, said optical element comprising:

a first element arranged for collimation of a fast axis of the laser beam emission; and

a second element arranged for rotation of the laser beam emission by substantially ±

90°

, characterized in that both said first and second elements are optically bonded to each other constituting at least a quasi-monolithic single optical element.

2. The optical element according to claim 1, wherein both elements constitute a single monolithic element.

3. The optical element according to claim 1, wherein said second element constitutes an array of optical beam rotation elements, optically bonded to each other constituting at least a quasi-monolithic single optical element.

4. The optical element according to claim 3, wherein said second element constitutes a single monolithic array of optical beam rotation elements.

5. The optical element according to claim 1, further comprising a third element for collimation of a slow axis of the laser beam emission,

characterized in that said third optical element is optically bonded to either side of said second element constituting at least a quasi-monolithic single optical element.

6. The optical element according to claim 5, wherein all three elements constitute a single monolithic element.

7. The optical element according to claim 5, wherein said third element constitutes a planar grin lens.

8. The optical element according to claim 5, wherein said third element constitutes a planar grin lens array.

9. The optical element according to claim 5, wherein said third element constitutes a surface curved in both or either of the directions orthogonal to the propagation direction.

10. The optical element according to claim 5, wherein said third element constitutes a multi-facet surface in both or either of the directions orthogonal to the propagation direction curved in both or either of the directions orthogonal to the propagation direction.

11. An optical element according to claim 5, further comprising cylindrical, spherical or aspherical lenses for coupling the diode beam into an optical fiber.

12. An optical element according to claim 1, further comprising cylindrical, spherical or aspherical lenses for coupling the diode beam into an optical fiber.

13. The optical element according to claim 1, further comprising a third element for collimation or expansion of the beam-rotated fast axis of the diode laser, characterized in that said third optical element is optically bonded to said second element constituting a quasi-monolithic single optical element.

14. The optical element according to claim 13, wherein said first, second and third elements constitute a single monolithic element.

15. The optical element according to claim 1, further comprising a third element for simultaneous (i) collimation of a slow axis of the laser beam emission and (ii) collimation of the laser beam emission after said rotation of said fast axis of the diode laser, characterized in that said third optical element is optically bonded to said second element constituting a quasi-monolithic single optical element.

16. The optical element according to claim 15, wherein said first, second and third elements constitute a single monolithic element.

17. The optical element according to claim 1, where said first element constitutes a planar grin lens.

18. The optical element according to claim 1, wherein said first element constitutes a uni-axial optical element with its optical axis aligned parallel to a slow axis of the diode laser axis, said first element further comprising a curved input surface and a flat output surface.

19. The optical element according to claim 1, wherein said second element constitutes a planar grin lens array.

20. The planar grin lens array according to claim 19, wherein a pitch of said planar grin lens array is equal to approximately 0.5.

21. The planar grin lens array according to claim 19, wherein planes of equal refractive index in said planar grin lens array are aligned at an angle of substantially ±

45°

with respect to a plane defined by a propagation direction of said laser beam emission and a slow axis of the diode laser.

22. The planar grin lens array according to claim 21, wherein a pitch of said planar grin lens array is equal to approximately 0.5.

23. An optical device comprising:

a plurality of optical elements for shaping a respective laser beam emission of a respective diode laser, each of said optical elements including (i) a first component element arranged for collimation of a fast axis of a respective laser beam emission and (ii) a second component element arranged for rotation of a respective laser beam emission by substantially ±

90°

;

respective pairs of said first and second component elements optically bonded to each other to form at least a quasi-monolithic single optical element;

said optical elements coupled into a multiple of optical fibers aligned in an optical fiber bundle so as to provide at least one combined beam of high optical power.