title: Enhanced pump absorption efficiency in coiled and twisted double-clad thulium-doped fibers.
abstract: Results of the first experimental demonstration of the recently proposed technique for improvement of the pump absorption in double-clad fibers by their simultaneous coiling and twisting are reported. The peak absorption (14 dB) of 3-m long hexagonal thulium-doped fiber was increased by 8 dB by its simultaneous coiling and twisting. Explanation of the effect is given by numerical modelling of the pump absorption in hexagonal and panda-type double-clad fibers. Improvement of fiber laser performance was also proved. The slope efficiency increased from 19.6% of the straight fiber to 23.9% of the coiled only fiber and 29.4% of the simultaneously coiled and twisted fiber.
authors.forename: Pavel
authors.initials: P
authors.lastname: Koška
authors.forename: Pavel
authors.initials: P
authors.lastname: Peterka
authors.forename: Jan
authors.initials: J
authors.lastname: Aubrecht
authors.forename: Ondřej
authors.initials: O
authors.lastname: Podrazký
authors.forename: Filip
authors.initials: F
authors.lastname: Todorov
authors.forename: Martin
authors.initials: M
authors.lastname: Becker
authors.forename: Yauhen
authors.initials: Y
authors.lastname: Baravets
authors.forename: Pavel
authors.initials: P
authors.lastname: Honzátko
authors.forename: Ivan
authors.initials: I
authors.lastname: Kašík