Photonic-crystal-rod optical amplifier with sealed-hole endcap and associated method

• US 7,835,068 B1
• Filed: 05/27/2006
• Issued: 11/16/2010
• Est. Priority Date: 07/29/2005
• Status: Active Grant

• Current Assignee: Lockheed Martin Aculight Corp. (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Di Teodoro, Fabio, Brooks, Christopher D.
• Primary Examiner(s): BOLDA, ERIC L
• Application Number:
  US11/420,750
• Time in Patent Office: 1,634 Days
• Field of Search: 359/341.1, 385/51, 385/126
• US Class Current: 359/341.1
• CPC Class Codes: C03B 37/10 Non-chemical treatment surface treatment of fibres or filaments made from glass, minerals or slags C03C25/00
• CPC Class Codes: G02B 6/02328 Hollow or gas filled core
• CPC Class Codes: G02B 6/02347 Longitudinal structures arranged to form a regular periodic lattice, e.g. triangular, square, honeycomb unit cell repeated throughout cladding
• CPC Class Codes: G02B 6/02376 Longitudinal variation along fibre axis direction, e.g. tapered holes
• CPC Class Codes: G02B 6/02385 Comprising liquid, e.g. fluid filled holes
• CPC Class Codes: G02B 6/3826 characterised by form or shape
• CPC Class Codes: G02B 6/3853 Lens inside the ferrule lensed connectors G02B6/32
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/0064 Anti-reflection devices, e.g. optical isolaters absorbing layers for marking or protecting purposes in laser working B23K26/50; magneto-optical non-reciprocal devices G02F1/093, G02F1/0955
• CPC Class Codes: H01S 3/0078 Frequency filtering
• CPC Class Codes: H01S 3/06704 Housings; Packages
• CPC Class Codes: H01S 3/06708 Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering optical fibres as passive waveguides G02B6/02
• CPC Class Codes: H01S 3/06729 Peculiar transverse fibre profile
• CPC Class Codes: H01S 3/06741 Photonic crystal fibre, i.e. the fibre having a photonic bandgap
• CPC Class Codes: H01S 3/06745 Tapering of the fibre, core or active region
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/06758 Tandem amplifiers
• CPC Class Codes: H01S 3/094007 Cladding pumping, i.e. pump light propagating in a clad surrounding the active core

Abstract

A method and apparatus use a photonic-crystal fiber having a very large core while maintaining a single transverse mode. In some embodiments, the method and apparatus includes a photonic-crystal fiber or rod (PCF or PCR) optical device having a beam-expanding endcap formed, e.g., by collapsing or otherwise sealing holes of the PCF or PCR. In some fiber lasers and amplifiers having large cores problems exist related to energy being generated at multiple-modes (i.e., polygamy), and of mode hopping (i.e., promiscuity) due to limited control of energy levels and fluctuations. The problems of multiple-modes and mode hopping result from the use of large-diameter waveguides, and are addressed by the invention. This is especially true in lasers using large amounts of energy (i.e., lasers in the one-megawatt or more range).

Claims

1. An apparatus comprising:

a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from at or near a first end of the device to at or near a second end of the device, wherein the holes are sealed at the second end of the device to form a beam-expanding endcap, and wherein the beam-expanding endcap includes an optical-exit facet at the second end that is polished after the holes are sealed.

25. The apparatus of claim of claim 1, wherein the photonic-crystal optical device is a first photonic-crystal optical device of a plurality of photonic-crystal optical devices contained within a photonic-crystal-rod (PCR) ribbon, and wherein each of the plurality of devices in the PCR ribbon is substantially similar to the first photonic-crystal optical device.

26. The apparatus of claim 25, wherein each one of the plurality of photonic-crystal optical devices emits an output beam such that the PCR ribbon emits a plurality of output beams, the apparatus further comprising:

a lens configured to form the plurality of output beams into a plurality of parallel beams;

a first diffraction grating configured to converge the plurality of parallel beams; and

a second diffraction grating configured to diffract the converged plurality of beams into a single spectrally combined output beam.

2. An apparatus comprising:

a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from at or near a first end of the device to at or near a second end of the device, wherein the holes are sealed at the second end of the device to form a beam-expanding endcap,—

wherein the device is a first photonic-crystal rod (PCR) having an outer diameter of at least 1 mm.

3. The apparatus of claim 2, wherein the holes are sealed to a distance of at least 1 mm from the second end of the first PCR device.

4. The apparatus of claim 2, wherein the holes are collapsed to a distance of at least 1 mm from the second end of the first PCR device.

5. The apparatus of claim 2, wherein the holes are filled with an index-matching material to a distance of at least 1 mm from the second end of the first PCR device.

6. An apparatus comprising:

a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from at or near a first end of the device to at or near a second end of the device, wherein the holes are sealed at the second end of the device to form a beam-expanding endcap,

wherein the device is a first photonic-crystal rod (PCR) having an outer diameter of at least 1 mm, and

wherein the endcap of the first PCR is formed to a diameter smaller than a diameter of the first PCR away from the endcap, and a facet is formed at an end of the endcap of the first PCR.

7. The apparatus of claim 6, further comprising a second photonic-crystal rod having an endcap that is formed to a diameter smaller than a diameter of the second PCR away from the endcap, and having a facet formed on the endcap of the second PCR, wherein the endcap of the first PCR is placed side-by-side to the endcap of the second PCR such that the end facet of the first PCR and the end facet of the second PCR are placed at a center-to-center distance closer than the diameter of the first PCR away from the endcap of the first PCR.

8. An apparatus comprising:

A photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from at or near a first end of the device to at or near a second end of the device, wherein the holes are sealed at the second end of the device to form a beam-expanding endcap, the apparatus further comprising a solid-glass endcap that is laser-welded to the second end of the photonic-crystal optical device.

9. A photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from at or near a first end of the device to at or near a second end of the device, wherein the holes are sealed at the second end of the device to form a beam-expanding endcap, the apparatus further comprising a solid-glass endcap that is fused to the second end of the photonic-crystal optical device.

10. An apparatus comprising:

a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device;

means for sealing the holes for a distance from the second end of the device to form a beam-expanding endcap; and

means for polishing an optical-exit facet at the second end after the holes are sealed by the means for sealing.

11. An apparatus comprising:

a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device; and

means for sealing the holes for a distance from the second end of the device to form a beam-expanding endcap, wherein the means for sealing comprises a fiber-splicing device.

12. An apparatus comprising:

a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device; and

means for sealing the holes for a distance from the second end of the device to form a beam-expanding endcap, wherein the device is a first photonic-crystal rod (PCR) having an outer diameter of at least 1 mm; and

wherein the means for sealing comprises;

means for melting the holes shut to a distance of at least 1 mm from the second end of the first PCR device; and

means for polishing an optical exit facet on the sealed end.

13. An apparatus comprising:

a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device; and

means for sealing the holes for a distance from the second end of the device to form a beam-expanding endcap, wherein the device is a first photonic-crystal rod (PCR) having an outer diameter of at least 1 mm; and

wherein the means for sealing comprises;

means for temporarily sealing the holes at the second end with an epoxy;

means for tapering a diameter of the second end;

means for removing the epoxy seal;

means for melting the holes shut at the second end; and

means for faceting the second end.

14. An apparatus comprising:

a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device; and

means for sealing the holes for a distance from the second end of the device to form a beam-expanding endcap, wherein the device is a first photonic-crystal rod (PCR) device, and wherein the means for sealing comprises means for laser-welding a solid-glass endcap to the second end of the first PCR device.

15. A method comprising:

providing a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device;

sealing the holes for a distance from the second end of the device to form a beam-expanding endcap; and

after the sealing of the holes, polishing an optical-exit facet at the second end.

16. The method of claim 15, wherein the sealing comprises melting the holes shut at the second end to form a solid-glass beam-expanding endcap.

20. The method of claim 15, wherein the sealing comprises sealing the holes to a distance of at least 1 mm from the second end of the photonic-crystal optical device.

17. A method comprising:

providing a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device;

sealing the holes for a distance from the second end of the device to form a beam-expanding endcap, wherein the device is a first photonic-crystal rod (PCR) having an outer diameter of at least 1 mm; and

wherein the sealing comprises;

melting the holes shut to a distance of at least 1 mm from the second end of the first PCR device; and

polishing an optical exit facet on the sealed end.

18. A method comprising:

providing a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device;

sealing the holes for a distance from the second end of the device to form a beam-expanding endcap, wherein the device is a first photonic-crystal rod (PCR) having an outer diameter of at least 1 mm; and

wherein the sealing comprises;

affixing a temporary seal to the holes at the second end;

reducing a diameter of the second end;

removing the temporary seal;

melting the holes shut at the second end; and

faceting the second end.

19. A method comprising:

providing a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device;

sealing the holes for a distance from the second end of the device to form a beam-expanding endcap, wherein the device is a first photonic-crystal rod (PCR) having an outer diameter of at least 1 mm; and

wherein the sealing comprises;

temporarily sealing the holes at the second end with an epoxy;

tapering a diameter of the second end;

removing the epoxy seal;

melting the holes shut at the second end; and

faceting the second end.

21. A method comprising:

providing a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device;

sealing the holes for a distance from the second end of the device to form a beam-expanding endcap, wherein the sealing comprises collapsing the holes to a distance of at least 1 mm from the second end of the photonic-crystal optical device; and

after the sealing of the holes, polishing an optical-exit facet at the second end.

22. A method comprising:

providing a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device; and

sealing the holes for a distance from the second end of the device to form a beam-expanding endcap, wherein the sealing comprises collapsing the holes to a distance of at least 1 mm from the second end of the photonic-crystal optical device, wherein the device is a first photonic-crystal rod (PCR) device, and wherein the sealing comprises laser-welding a solid-glass endcap to the second end of the first PCR device.

23. A method comprising:

providing a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device; and

sealing the holes for a distance from the second end of the device to form a beam-expanding endcap, wherein the sealing comprises collapsing the holes to a distance of at least 1 mm from the second end of the photonic-crystal optical device, wherein the device is a first photonic-crystal rod (PCR) device, and wherein the sealing comprises fusing a solid-glass endcap to the second end of the first PCR device.

24. A method comprising:

providing a photonic-crystal optical device having a core surrounded by a plurality of lengthwise holes that extend from a first end of the device to a second end of the device; and

sealing the holes for a distance from the second end of the device to form a beam-expanding endcap, wherein the sealing comprises collapsing the holes to a distance of at least 1 mm from the second end of the photonic-crystal optical device, wherein the device is a first photonic-crystal rod (PCR) device, and wherein the sealing comprises filling the holes with an index-matching material to a distance of at least 1 mm from the second end of the first PCR device.