Packaged laser diode array system and method with reduced asymmetry

• US 6,044,096 A
• Filed: 11/03/1997
• Issued: 03/28/2000
• Est. Priority Date: 11/03/1997
• Status: Expired due to Fees

• Current Assignee: JDS Uniphase Corporation (Lumentum Holdings Inc.)
• Original Assignee: SDL Inc (RWS Holdings Plc)
• Inventors: Wolak, Edmund L., Endriz, John G.
• Primary Examiner(s): Davie, James W.
• Application Number:
  US08/962,768
• Time in Patent Office: 876 Days
• Field of Search: 372/101, 372/43, 372/108, 372/36, 372/34, 372/109, 428/196, 356/153
• US Class Current: 372/36
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• 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: G02B 27/143 using macroscopically faceted or segmented reflective surfaces
• 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 5/4025 Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence

Abstract

A system and method for operating a high power laser diode device with high efficiency coupling of a laser diode bar. The laser diode bar and a micro-cylinder lens are vertically oriented in a device package, such that the array axis of the laser bar and the longitudinal axis of the micro-cylinder lens are aligned substantially parallel to a gravity vector. In the two different embodiments disclosed, either initial collimation of the fast-axis divergence or, alternatively, initial collimation of both the fast-axis and slow-axis divergences take place before beam reformatting via a beam array turning mirror. Additionally, the vertical orientation of these components is combined with methods of compensating for the bending or "smile" of the laser diode bar to provide for optimal output beam coupling, resulting in a uniform far field intensity distribution.

Claims

1. A method for efficient collimation of an aligned multiple beam output coupled from a diode laser bar to a lens system to conserve source brightness and output uniformity, comprising the steps of:

orienting the laser diode bar having multiple beam outputs substantially in straight-line alignment in a manner that its longitudinal length is aligned along a direction substantially parallel to a gravity vector; and

orienting the lens system in a manner that its longitudinal axis is aligned along a direction substantially parallel to the gravity vector so that both the laser diode bar and the lens system are prevented from sagging as in the case where its longitudinal axis is aligned along a direction substantially perpendicular to the gravity vector so that substantially straight-line alignment of the lens system is maintained with the straight-line alignment of the multiple beam outputs.

2. The method of claim 1, further comprising the step of:

compensating for a bending of the laser diode bar by applying a varying bias current to a plurality of thermal load elements, wherein the laser bar comprises a plurality of laser diode sources and a plurality of thermal load elements, wherein each thermal load element is in direct contact with one of the plurality of laser diode sources, and wherein the bias current is varied corresponding to a far field intensity distribution the light output from the laser bar.

3. The method of claim 1, wherein at least two of the plurality of individual laser diode sources are offset relative to each other with respect to the longitudinal axis, further comprising the step of:

compensating for a bending of the laser diode bar by changing a current applied to a first offset source relative to the current applied to a second offset source, wherein after the change in current, a far field intensity distribution profile of the output beam is uniform.

4. A multiple light beam assembly providing for high output beam coupling efficiency through enhanced beam alignment and uniformity, comprising:

a laser diode bar having a plurality of individual laser diode sources providing multiple beam outputs substantially aligned along a longitudinal axis of said bar, said laser diode array oriented substantially parallel to a gravity vector so that the sagging of the laser diode bar is prevented providing a substantially straight-line alignment of the multiple beam outputs oriented along the gravity vector; and

a lens system optically coupled to receive said straight-line alignment of the multiple beam outputs of said laser diode bar and collimate said outputs in a least one orthogonal direction, a longitudinal axis of said lens system oriented substantially parallel to the gravity vector so that the sagging of the lens system is also prevented so that substantially straight-line alignment of the lens system is maintained with the straight-line alignment of the multiple beam outputs.

5. The multiple light beam assembly of claim 4, wherein said array further comprises:

a plurality of thermal load elements coupled to said plurality of laser diode sources.

6. The multiple light beam assembly of claim 5, wherein said array further comprises:

a power source supply for providing a bias current independently to said plurality of laser diode sources and said plurality of thermal load elements.

7. The multiple light beam assembly of claim 6, wherein said bias current to either said sources or to said thermal load elements is variable.

8. The multiple light beam assembly of claim 4, wherein at least two of said plurality of individual laser diode sources are offset from each other relative to said bar longitudinal axis, an emitted intensity of each of said offset sources being altered to alter a far field intensity distribution profile of said multiple beam output to render the profile more uniform.

9. The multiple light beam assembly of claim 4, wherein said lens system comprises a lens for collimating a fast-axis divergence of said diode laser array.

10. The multiple light beam assembly of claim 9, wherein said lens system comprises a cylinder lens.

11. The multiple light beam assembly of claim 10, wherein said cylinder lens is a D-shaped cylindrical lens.

12. The multiple light beam assembly of claim 4, wherein said lens system comprises at least one lens for collimating both a fast-axis and a slow-axis divergence of said diode laser bar.

13. The multiple light beam assembly of claim 4, wherein said assembly further comprises:

a turning mirror optically coupled to receive said collimated multiple beam output from said lens system and reformat said orientation and alignment of said multiple beam output of said laser diode bar.

14. The multiple light beam assembly of claim 13, wherein said orientation is 90°

rotation of individual beams comprising said multiple beam output with their re-alignment one above another.

15. The multiple light beam assembly of claim 13, wherein the assembly further comprises:

a beam-fill optics optically coupled to receive said multiple beam output from said turning mirror to provide an output having the appearance of a single virtual source comprising said multiple beam output.

16. The multiple light beam assembly of claim 15, further comprising:

a further lens optically coupled to receive the multiple beam output from said beam-fill optics and collimate said output in at least another orthogonal direction.

17. The multiple light beam assembly of claim 16, wherein said lens system collimates said multiple beam output fast-axis divergence and said further lens collimates said multiple beam output slow-axis divergence.

18. The multiple light beam assembly of claim 16, wherein said assembly further comprises:

a focusing lens optically coupled to receive said multiple beam output from said further lens to focus said output to a diffraction limited spot.

19. A multiple light beam assembly providing for high output beam coupling efficiency, comprising:

a laser diode bar having a plurality of individual laser diode sources providing multiple beam outputs substantially aligned along a longitudinal axis of said bar, said laser diode array oriented substantially parallel to a gravity vector so that the sagging of the laser diode bar is prevented providing a substantially straight-line alignment of the multiple beam outputs oriented along the gravity vector; and

a lens system optically coupled to receive said aligned multiple beam output of said laser diode bar comprising a first lens to collimate said aligned multiple beam output in a first orthogonal direction and a second lens to collimate said aligned multiple beam output in a second orthogonal direction, a longitudinal axis of both of said lens oriented substantially parallel to the gravity vector so that the sagging of the lens system is also prevented so that substantially straight-line alignment of the lens system is maintained with the straight-line alignment of the multiple beam outputs; and

a turning mirror optically coupled to receive the orthogonally collimated multiple beam output from said lens system and reformat the orientation of multiple beam output of said laser diode bar.

20. The multiple light beam assembly of claim 19 further comprising a beam filling optics following said turning mirror to format the individual beams into a uniform field appearing as a single beam output.