Efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser

Abstract

A novel approach to achieving robust single-spatial-mode operation of cladding-pumped fiber lasers with multimode cores is reported. The approach is based on the use of a fiber geometry in which the core has a helical trajectory within the inner cladding to suppress laser oscillation on higher-order modes. In a preliminary proof-of-principle study, efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser with a 30 microm diameter core and a numerical aperture of 0.087 has been demonstrated. The laser yielded 60.4 W of output at 1043 nm in a beam with M2 < 1.4 for 92.6 W launched pump power from a diode stack at 976 nm. The slope efficiency at pump powers well above threshold was approximately 84%, which compares favorably with the slope efficiencies achievable with conventional straight-core Yb-doped double-clad fiber lasers.

Twist-induced guidance in coreless photonic crystal fiber: A helical channel for light

“…Chiral fibers with cores have been studied since the 1980s, for example, in connection with circular birefringence ( 3 , 4 ), current sensing ( 5 , 6 ), and elimination of higher-order modes in fiber lasers using helical off-axis cores ( 7 , 8 ). Twisted multicore PCFs have been shown to support helical Bloch waves and to exhibit orbital angular momentum (OAM) birefringence ( 9 ).…”

Design of an All-Fiber Device for Exciting a Single LP0,n Mode in a Multimode Fiber

“…The wavelengths for exciting single LP 0,2 , LP 0,3 and LP 0,4 modes in MMF2 are shown in table 1. To verify these results, we simulated the structure employing wide angle beam propagation method with padé order (4,4) [10] using a commercial software package (BeamProp, Rsoft, ver.9). Wavelengths to achieve maximum γ 2 , γ 3 and γ 4 at the same length of MMF1 are also presented in table 1.…”

“…Large modal area and SM propagation are crucial requirements in high power fiber lasers. Various techniques have already been suggested for achieving an SM in large core area MMFs [2,[4][5][6]. In addition to these techniques, phenomenon of multimode interference in MMFs is also effectively utilized to achieve SM laser beams from MMFs [7].…”

High efficiency single-mode-multimode-single-mode fiber laser with diffraction-limited beam output

“…There had been other methods developed to achieve high output power while maintaining diffraction-limited beam output. Some of them involved specialty active fiber design, such as a special refractive-index profile to achieve M 2 < 2.0 beam quality [3], ultrashort cavity length with highly doped fiber [4], large-core phosphate fiber with an intracavity spatial-mode filter [5], helical-core fibers with a core 1559-128X/14/245554-05$15.00/0 © 2014 Optical Society of America diameter of 30 μm [6], and leakage channel gain fiber of 3160 μm 2 effective core area [7]. The disadvantages of these methods are the use of specially designed large-mode-area (LMA) fibers that are not commercially available.…”