Результаты исследований: Публикации в книгах, отчётах, сборниках, трудах конференций › статья в сборнике материалов конференции › научная › Рецензирование
Comparison of multimode LD pump beam shaping in step-index and graded-index fibers and its influence on Raman lasing. / Kuznetsov, Alexey G.; Wolf, Alexey A.; Nemov, Ilya N. и др.
Micro-Structured and Specialty Optical Fibres VII. ред. / Kyriacos Kalli; Pavel Peterka; Christian-Alexander Bunge. SPIE, 2022. 121400F (Proceedings of SPIE - The International Society for Optical Engineering; Том 12140).Результаты исследований: Публикации в книгах, отчётах, сборниках, трудах конференций › статья в сборнике материалов конференции › научная › Рецензирование
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TY - GEN
T1 - Comparison of multimode LD pump beam shaping in step-index and graded-index fibers and its influence on Raman lasing
AU - Kuznetsov, Alexey G.
AU - Wolf, Alexey A.
AU - Nemov, Ilya N.
AU - Kablukov, Sergey I.
AU - Babin, Sergey A.
N1 - Funding Information: The study is supported by Russian Science Foundation (№21-72-30024). Publisher Copyright: © 2022 SPIE.
PY - 2022
Y1 - 2022
N2 - It is known that graded-index fibers (GIF) provide efficient Raman conversion of multimode radiation into a Stokes beam with improved beam quality known as Raman beam cleanup effect, whereas in step-index fibers (SIF) this effect is weak. Here we study propagation of low-coherent (~5 nm wide) highly-multimode (M2~30) pump radiation of high power 940-nm laser diodes (LDs) in GIF and SIF of ~100 µm core diameter. We measured pump beam shapes at the output of fibers with different length. It has been shown that the output beam shape is almost independent of the input pump beam shape approaching to rectangular or parabolic profile after propagation in only ten meters of SIF or GIF, respectively. The output beam shape mimics the refractive-index profile in the multimode fiber core due to random mode coupling. This means that Raman gain is nearly the same for all transverse modes in SIF and has maximum gain for the fundamental mode in GIF that is the main reason of strong Raman beam cleanup effect in GIF. We tested Raman lasing in 1-km GIF/SIF with 940-nm LD pumping of up to ~200 W power with a cavity formed by fiber Bragg gratings (FBGs). The output FBG fs-inscribed in GIF/SIF improves the output beam quality due to spatial filtering property, but in GIF the effect is much stronger.
AB - It is known that graded-index fibers (GIF) provide efficient Raman conversion of multimode radiation into a Stokes beam with improved beam quality known as Raman beam cleanup effect, whereas in step-index fibers (SIF) this effect is weak. Here we study propagation of low-coherent (~5 nm wide) highly-multimode (M2~30) pump radiation of high power 940-nm laser diodes (LDs) in GIF and SIF of ~100 µm core diameter. We measured pump beam shapes at the output of fibers with different length. It has been shown that the output beam shape is almost independent of the input pump beam shape approaching to rectangular or parabolic profile after propagation in only ten meters of SIF or GIF, respectively. The output beam shape mimics the refractive-index profile in the multimode fiber core due to random mode coupling. This means that Raman gain is nearly the same for all transverse modes in SIF and has maximum gain for the fundamental mode in GIF that is the main reason of strong Raman beam cleanup effect in GIF. We tested Raman lasing in 1-km GIF/SIF with 940-nm LD pumping of up to ~200 W power with a cavity formed by fiber Bragg gratings (FBGs). The output FBG fs-inscribed in GIF/SIF improves the output beam quality due to spatial filtering property, but in GIF the effect is much stronger.
KW - beam clean-up
KW - diode pumping
KW - FBG
KW - fiber laser
KW - graded-index fiber
KW - mode selection
KW - multimode
KW - pump depletion
KW - Raman laser
KW - random coupling
KW - step-index fiber
UR - http://www.scopus.com/inward/record.url?scp=85134465508&partnerID=8YFLogxK
UR - https://www.mendeley.com/catalogue/136686b1-d9df-3de0-907c-e5f2eaac05dd/
U2 - 10.1117/12.2622184
DO - 10.1117/12.2622184
M3 - Conference contribution
AN - SCOPUS:85134465508
SN - 9781510651562
T3 - Proceedings of SPIE - The International Society for Optical Engineering
BT - Micro-Structured and Specialty Optical Fibres VII
A2 - Kalli, Kyriacos
A2 - Peterka, Pavel
A2 - Bunge, Christian-Alexander
PB - SPIE
T2 - Micro-Structured and Specialty Optical Fibres VII 2022
Y2 - 9 May 2022 through 20 May 2022
ER -
ID: 36710087