Thulium-doped fiber performance optimization via fiber bending and twisting and inner-cladding shape design

O. Schreiber; J. Aubrecht; A. A. Jasim; F. Todorov; P. Honzátko

doi:10.1117/12.2592309

18 April 2021 Thulium-doped fiber performance optimization via fiber bending and twisting and inner-cladding shape design

O. Schreiber, J. Aubrecht, A. A. Jasim, F. Todorov, P. Honzátko

Author Affiliations +

Proceedings Volume 11773, Micro-structured and Specialty Optical Fibres VII; 117731A (2021) https://doi.org/10.1117/12.2592309
Event: SPIE Optics + Optoelectronics, 2021, Online Only

Conference Poster

Abstract

Thulium-doped fiber lasers have been extensively investigated as the most promising source of efficient laser emission at wavelengths around 2 μm, i. e., in the eye-safer spectral region and in the atmospheric window as well. It allows for wide range of applications including medicine, defense, distance measurement or materials processing. To enhance pump absorption efficiency along the active double-clad fiber, good overlap of the pump light and doped fiber core should be achieved along the fiber length. The overlap can be increased by breaking the circular symmetry of the inner cladding by shaping its cross-section. Further mode-mixing and better pump absorption can be achieved by coiling and twisting of double-clad fibers. In this work we present experimental measurement of 792 nm pump cladding absorption of a series of double-clad thuliumdoped fibers with respect to their bend radius, the inner cladding cross-sectional shape and twist rate. With these fibers, we assembled a set of fiber lasers with different resonator setups and tested their performance. Twisting was introduced to fiber during drawing from an octagonal, CO2 laser-shaped or mechanically grinded preform so that the twist remained frozen in the drawn fiber. We have shown that the fiber twist significantly improves the pump absorption even in the case of straight or coiled fibers with large coil radii. We provide a preliminary comparison of two fiber laser resonators.

Conference Presentation

Citation Download Citation

O. Schreiber, J. Aubrecht, A. A. Jasim, F. Todorov, and P. Honzátko "Thulium-doped fiber performance optimization via fiber bending and twisting and inner-cladding shape design", Proc. SPIE 11773, Micro-structured and Specialty Optical Fibres VII, 117731A (18 April 2021); https://doi.org/10.1117/12.2592309

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