Abstract
A pump-coupling architecture is disclosed for high-power cladding-pumped fiber lasers to mitigate transverse mode instability (TMI) by flattening the longitudinal heat load. A continuous, longitudinally distributed diffraction grating is formed along the full pumped length of the outer surface of the inner cladding of a double-clad fiber, rather than at a single coupling point. Pump light launched at one end into the outer cladding is progressively coupled into the inner cladding. The local coupling coefficient A(z) is derived analytically by solving an inverse thermal-design problem: a target heat-generation profile is prescribed, here a spatially uniform one, and the required coupling profile is obtained. For single-end pumping under an instantaneous-absorption approximation this gives the closed-form hyperbolic profile A(z) = 1/(L-z), in contrast to the exponentially decaying heat profile of Beer-Lambert absorption. The grating combines apodization for thermal shaping with chirp for spectral bandwidth and robustness to pump diode wavelength drift, and in a preferred embodiment an asymmetric blazed or tilted fringe profile for unidirectional coupling. The method generalizes via fiber-laser rate equations to arbitrary prescribed thermal distributions and spectrally non-uniform pump sources, and extends to fiber amplifiers, nonlinear waveguide devices, RF and microwave waveguides, and acoustic waveguides. Disclosed in South African provisional patent application No. 2026/06916, filed 6 July 2026. Parties interested in collaboration, licensing or development during the priority period are invited to contact the author at [email protected].
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
ARIELI, YOEL SHIMO, "Apodized Chirped Cladding Grating for Uniform Thermal Load Distribution in High-Power Fiber Lasers (Mitigating Transverse Mode Instability)", Technical Disclosure Commons, (October 21, 2026)
https://www.tdcommons.org/dpubs_series/12360