Photonic-crystal-rod amplifiers for high-power pulsed optical radiation and associated method

• US 7,379,237 B1
• Filed: 05/27/2006
• Issued: 05/27/2008
• Est. Priority Date: 07/29/2005
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Aculight Corp. (Martin Marietta Corporation)
• Original Assignee: Aculight Corporation (Martin Marietta Corporation)
• Inventors: Di Teodoro, Fabio, Brooks, Christopher D.
• Primary Examiner(s): Hughes; Deandra M
• Application Number:
  US11/420,746
• Time in Patent Office: 731 Days
• Field of Search: 359/341.1, 385/126
• US Class Current: 359/341.41
• 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 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). By using multiple small waveguides in parallel, large amounts of energy can be passed through a laser, but with better control such that the aforementioned problems can be reduced. An additional advantage is that the polarization of the light can be maintained better than by using a single fiber core.

Claims

1. An apparatus comprising:

a photonic-crystal rod (PCR) having rare-earth-doped core with a diameter of at least 40 microns and an external diameter of at least 1 mm such that the rod is therefore thick enough to substantially and readily hold its shape when released, wherein the apparatus is operable to obtain optical pulses from the rod having a peak power of at least five hundred kilowatts (500 kW).

2. The apparatus of claim 1, wherein the core of the PCR has a diameter of at least 50 microns.

3. The apparatus of claim 1, wherein the core of the PCR has a diameter of at least 70 microns.

4. The apparatus of claim 1, wherein the core of the PCR has a diameter of at least 100 microns.

5. The apparatus of claim 1, wherein the apparatus is operable to obtain optical pulses from the rod having a peak power of at least two megawatts (2 MW).

6. The apparatus of claim 1, wherein the apparatus is operable to obtain optical pulses from the rod having a beam-quality M² value of less than 1.5.

7. The apparatus of claim 1, wherein the core of the PCR has a diameter of at least 70 microns and is Ytterbium (Yb) doped, and is operable to obtain optical pulses of peak power at least three megawatts (3 MW), a beam-quality M² value of less than 1.5, and a spectral linewidth of less than 13 GHz.

8. The apparatus of claim 1, wherein the core of the PCR has a diameter of at least 100 microns and is Ytterbium (Yb) doped, and is operable to generate optical pulses of peak power at least four megawatts (4 MW), a beam-quality M² value of less than 1.5, and a spectral linewidth of less than 20 GHz.

9. The apparatus of claim 1, wherein the core of the PCR is Ytterbium (Yb) doped, and is operable to generate linearly polarized optical pulses of peak power at least one hundred kilowatts (100 kW), and a degree of polarization of at least 15 dB (wherein the degree of polarization is a value of ten times the log (base 10) of the ratio of optical power along the polarization axis to the optical power along the orthogonal axis).

10. The apparatus of claim 1, further comprising at least one wavelength-conversion optical medium operable to receive high-peak-power input radiation having a first wavelength from the core of the rod and to generate radiation of a different second wavelength having a peak power of at least about 100 kW through wavelength conversion.

26. The apparatus of claim 1, wherein the core of the PCR has a diameter of at least 125 microns.

27. The apparatus of claim 1, wherein the core of the PCR has a diameter of at least 150 microns.

28. The apparatus of claim 1, wherein the core of the PCR has a diameter of at least 200 microns.

29. The apparatus of claim 1, wherein the apparatus emits optical pulses from the rod having a peak power of at least two megawatts (2 MW).

30. The apparatus of claim 1, wherein the apparatus emits optical pulses from the rod having a beam-quality M² value of less than 1.5.

31. The apparatus of claim 1, wherein the core of the PCR has a diameter of at least 70 microns and is Ytterbium (Yb) doped, and outputs optical pulses of peak power at least three megawatts (3 MW), a beam-quality M² value of less than 1.5, and a spectral linewidth of less than 13 GHz.

32. The apparatus of claim 1, wherein the PCR emits a linearly polarized output beam of wavelength in the 1.0-1.1-micron range and single-transverse-mode, near-diffraction-limited quality, and pulse peak power in excess of 1 MW, pulse energy in excess of 1 mJ, and pulse spectral linewidth less than 50 GHz.

11. A method comprising:

providing a photonic-crystal rod (PCR) having rare-earth-doped core with a diameter of at least 40 microns and an external diameter of at least 1 mm; and

amplifying optical pulses with the rod to generate pulses having a peak power of at least five hundred kilowatts (500 kW).

12. The method of claim 11, wherein the core of the PCR has a diameter of at least 50 microns.

13. The method of claim 11, wherein the core of the PCR has a diameter of at least 70 microns.

14. The method of claim 11, wherein the core of the PCR has a diameter of at least 100 microns.

15. The method of claim 11, wherein the amplifying generates optical pulses from the rod having a peak power of at least two megawatts (2 MW).

16. The method of claim 11, wherein the amplifying generates optical pulses from the rod having a beam-quality M² value of less than 1.5.

17. The method of claim 11, wherein the amplifying generates optical pulses of peak power at least three megawatts (3 MW), a beam-quality M² value of less than 1.5, and a spectral linewidth of less than 13 GHz.

18. The method of claim 11, wherein the amplifying generates optical pulses of peak power at least four megawatts (4 MW), a beam-quality M² value of less than 1.5, and a spectral linewidth of less than 20 GHz.

19. The method of claim 11, wherein the core of the PCR is Ytterbium (Yb) doped, and wherein the amplifying generates linearly polarized optical pulses of peak power at least one hundred kilowatts (100 kW), and a degree of polarization of at least 15 dB (wherein the degree of polarization is a value of ten times the log (base 10) of the ratio of optical power along the polarization axis to the optical power along the orthogonal axis).

20. The method of claim 11, further comprising:

receiving high-peak-power input radiation having a first wavelength from the PCR; and

performing wavelength-conversion to generate radiation of a different second wavelength and having a peak power of at least about 100 kW.

33. The method of claim 11, further comprising

emitting from the PCR a linearly polarized output beam of wavelength in the 1.0-1.1-micron range and single-transverse-mode, near-diffraction-limited quality, and pulse peak power in excess of 1 MW, pulse energy in excess of 1 mJ, and pulse spectral linewidth less than 50 GHz.

21. An apparatus comprising:

a photonic-crystal rod (PCR) having rare-earth-doped core with a diameter of at least 50 microns and an external diameter of at least 1 mm; and

means for amplifying optical pulses with the rod to generate pulses having a peak power of at least five hundred kilowatts (500 kW).

22. The apparatus of claim 21, wherein the means for amplifying generates optical pulses from the rod having a peak power of at least two megawatts (2 MW).

23. The apparatus of claim 21, wherein the means for amplifying generates optical pulses of peak power at least four megawatts (4 MW), a beam-quality M² value of less than 1.5, and a spectral linewidth of less than 20 GHz.

24. The apparatus of claim 21, wherein the core of the PCR is Ytterbium (Yb) doped, and the means for amplifying generates linearly polarized optical pulses of peak power at least one hundred kilowatts (100 kW), and a degree of polarization of at least 15 dB (wherein the degree of polarization is a value of ten times the log (base 10) of the ratio of optical power along the polarization axis to the optical power along the orthogonal axis).

25. The apparatus of claim 21, further comprising:

means for performing wavelength-conversion to generate radiation of a different second wavelength and having a peak power of at least about 100 kW.

34. The apparatus of claim 21, wherein the PCR emits a linearly polarized output beam of wavelength in the 1.0-1.1-micron range and single-transverse-mode, near-diffraction-limited quality, and pulse peak power in excess of 1 MW, pulse energy in excess of 1 mJ, and pulse spectral linewidth less than 50 GHz.