Segmented acoustic core photonic crystal fiber laser

• US 7,822,314 B1
• Filed: 07/02/2008
• Issued: 10/26/2010
• Est. Priority Date: 07/02/2008
• Status: Expired due to Fees

• Current Assignee: US Department of The Air Force (U.S. Department Of Defense)
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Dajani, Iyad A., Shay, Thomas M., Robin, Craig A.
• Primary Examiner(s): Le; Uyen-Chau N
• Assistant Examiner(s): Bedtelyon; John M
• Application Number:
  US12/166,611
• Time in Patent Office: 846 Days
• Field of Search: 385/142, 359/334, 359/341.1, 359/341.5
• US Class Current: 385/142
• CPC Class Codes: G02B 6/02333 Core having higher refractive index than cladding, e.g. solid core, effective index guiding
• CPC Class Codes: G02B 6/02357 Property of longitudinal structures or background material varies radially and/or azimuthally in the cladding, e.g. size, spacing, periodicity, shape, refractive index, graded index, quasiperiodic, quasicrystals
• CPC Class Codes: G02B 6/02371 Cross section of longitudinal structures is non-circular
• CPC Class Codes: H01S 2301/03 Suppression of nonlinear conversion, e.g. specific design to suppress for example stimulated brillouin scattering [SBS], mainly in optical fibres in combination with multimode pumping
• 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

Abstract

Stimulated Brillouin scattering (SBS) in a photonic crystal fiber is suppressed by doping the individual core segments such that the Brillouin frequency of each segment is sufficiently different from the neighboring segments that Brillouin scattered light from one core segment sees negligible gain from the other core segments, whereby higher power narrow-linewidth optical fiber amplifiers and lasers may be obtained. The optical properties of the guiding medium are preserved through the careful design of the core and the lattice structure.

Claims

1. In a standard photonic crystal fiber comprised in cross-section of N uniformly doped, hexagon-shaped silica core segments enclosed by a cladding comprised of stress applying parts and air holes, the improvement comprising adding a plurality of non-rare earth dopants known to either raise or lower the acoustic index of refraction or the optical index of refraction or both to said N core segments selected in type and concentration such that the acoustic index of refraction of each core segment is changed to support N distinctly different peak Brillouin frequencies having no linewidth overlap while maintaining the same optical index of refraction for all N core segments, thereby enabling kilowatt-level narrow-linewidth fiber lasers and amplifiers.

2. The photonic crystal fiber improvement of claim 1, wherein said plurality of additional non-rare earth dopants includes two or more dopants selected from germanium, aluminum, fluorine, and phosphorous.

3. The photonic crystal fiber improvement of claim 1, wherein said claim 1 improvement is combined with a longitudinal thermal gradient to thereby further increase the stimulated Brillouin scattering threshold.