Top hat single-mode polarization maintaining fiber and polarizing numerical design

Compactness, long term stability and no free-space alignment are important advantages of fiber lasers over bulky systems. These fiber lasers have also demonstrated their capability to deliver high-power pulses and are thus suitable for numerous applications. Nevertheless the intensity profile delivered usually has a Gaussian-like shape, which most of the time is sufficient, but it could be interesting, for many applications (laser-biological tissues interactions, heat treatment, industrial laser processing or for seeding large-scale laser facilities like Laser MegaJoule) to obtain a homogeneous intensity profile at the fiber laser output. Moreover several of these applications required a linearly polarized output beam. In order to achieve all these requirements we have developed and realized a new fiber design. This fiber is the first polarization maintaining single-mode fiber delivering a flat top intensity. A high quality flat mode was obtained at 1.05μm through the use of a well-tailored index profile and single-mode behavior was verified by shifting the injection and using the S² imaging. Moreover, boron Stress Applying Parts (SAPs) including in the cladding led to a birefringence of 0.6x10-4 and a measured PER better than 20dB even for a long fiber length (~20 m). Alongside the fabrication, we developed a simulation code, using Comsol Multiphysics®, to take into account the stress dependency induced by the SAPs. Further modeling allows us to present an effectively single-mode fiber design, delivering a top-hat mode profile and exhibiting a polarizing behavior.

[1]  Fred M. Dickey,et al.  Laser Beam Shaping , 2003 .

[2]  R. Howard,et al.  A single-polarization fiber , 1983 .

[3]  P. Roberts,et al.  Stress induced birefringence in hybrid TIR/PBG guiding solid photonic crystal fibers. , 2010, Optics express.

[4]  Mitsunobu Miyagi,et al.  Beam homogenizer for hollow-fiber delivery system of excimer laser light. , 2003, Applied optics.

[5]  Fernando L. Teixeira,et al.  General closed-form PML constitutive tensors to match arbitrary bianisotropic and dispersive linear media , 1998 .

[6]  Arnaud Mussot,et al.  High-energy temporally shaped nanosecond-pulse master-oscillator power amplifier based on ytterbium-doped single-mode microstructured flexible fiber. , 2011, Optics letters.

[7]  David J. Richardson,et al.  High power fiber lasers: current status and future perspectives [Invited] , 2010 .

[8]  Ivan P. Kaminow,et al.  Single polarization optical fibers: slab model (A) , 1978 .

[9]  Stephen A. Payne,et al.  Large flattened-mode optical fiber for reduction of nonlinear effects in optical fiber lasers , 2004, SPIE LASE.

[10]  Laurent Bigot,et al.  Polarization maintaining single-mode fiber delivering a flat top intensity profile. , 2015, Optics express.

[11]  A Katzir,et al.  Silver-halide fiber tip as a beam homogenizer for infrared hollow waveguides. , 1997, Optics letters.

[12]  Arnaud Mussot,et al.  Top-hat beam output of a single-mode microstructured optical fiber: impact of core index depression. , 2013, Optics express.

[13]  Dexiu Huang,et al.  Stress birefringence analysis of polarization maintaining optical fibers , 2005 .

[14]  K. Okamoto,et al.  Polarization-maintaining fibers and their applications , 1986 .

[15]  W. Chew,et al.  Systematic derivation of anisotropic PML absorbing media in cylindrical and spherical coordinates , 1997 .

[16]  M. C. de Lignie,et al.  Large polarization mode dispersion in fiber optic cables , 1994 .

[17]  Laurent Bigot,et al.  Advanced S$^2$ Imaging: Application of Multivariate Statistical Analysis to Spatially and Spectrally Resolved Datasets , 2014, Journal of Lightwave Technology.

[18]  Arnaud Mussot,et al.  Top-hat beam output with 100 μJ temporally shaped narrow-bandwidth nanosecond pulses from a linearly polarized all-fiber system. , 2014, Optics letters.

[19]  A Tünnermann,et al.  Stress-induced birefringence in large-mode-area micro-structured optical fibers. , 2005, Optics express.

[20]  M Douay,et al.  Solid photonic bandgap fiber assisted by an extra air-clad structure for low-loss operation around 1.5 microm. , 2007, Optics express.

[21]  H. Bartelt,et al.  Ytterbium-Doping Related Stresses in Preforms for High-Power Fiber Lasers , 2009, Journal of Lightwave Technology.

[22]  Ajoy Ghatak,et al.  Design of a waveguide refractive index profile to obtain a flat modal field , 1999, Other Conferences.