Chirally Coupled Core Fibers at 1550-nm and 1064-nm for Effectively Single-Mode Core Size Scaling

Abstract

Novel index-guiding-core single-mode fibers with V >> 2.405 are demonstrated at 1550-nm and 1064-nm wavelengths. This fiber design is based on chirally-coupled core concept, which enables a new type of index-guiding and photonic-crystal fiber structures.OCIS codes: (060.2280) Fiber design and fabrication; (060.2320) Fiber optics amplifiers and oscillators Introduction.Recent advance of fiber laser technology into multi-kW average 1 and multi-MW peak 2, power generation in diffractionlimited output beams have been critically based on adopting so called Large-Mode Area (LMA) fibers, in which multimode fibers with large cores (typically 20-μm to 30-μm diameter, with 65-μm to 80-m state of the art demonstrations 2 ) are used with careful mode-management 3, 4 for achieving single-mode operation. This offsets many traditional technological advantages of conventional single-mode low-power fiber laser technology, hindering development of all-monolithic large-core fiber systems.

Yb-doped large-pitch fibres: effective single-mode operation based on higher-order mode delocalisation

“…Consequently, the HOMs can tunnel out of the core, which leads to the filtering of undesired power content along the fibre. Prominent representatives of this approach are chirally coupled core fibres 8 and Bragg fibres. 9 However, any resonant design is very challenging to produce (due to the tight tolerances that have to be normally matched), and it might fail due to some experimental constraints, e.g., a narrow transmission band or the effective-index changes that occur when pumping or bending the fibre.…”

Optimizing single mode robustness of the distributed modal filtering rod fiber amplifier

“…Degradation of beam quality is a critical factor for future power scaling of fiber optical lasers and amplifiers. An all solid fiber with chirally-coupled cores (CCC) has been demonstrated to increase the core diameter up to 33.5 μm and have effective SM operation by coupling all higher order modes (HOMs) of the central core into high-loss helix side modes [5,6]. The CCC fiber is dependent on fabrication parameters of the helix side core and further core scaling has yet to be seen.…”

Single-mode ytterbium-doped large-mode-area photonic bandgap rod fiber amplifier

“…For example, manufacturing of low-NA SM LMA Photonic Crystal Fibers (PCFs), using an air/silica microstructured cladding, has typically higher yield than the step-index approach and have successfully been applied in amplifier systems [1,2]. Another approach is to use Multi-Mode (MM) step-index fiber cores, where the Higher-Order-Modes (HOMs) are either suppressed by utilizing differential bend loss [3], chirally coupled cores [4] or differential mode loss in so-called leaky-channel fibers [5]. SM operation in highly MM fibers can also be obtained by matching the launched beam to the FM and carefully exciting the Fundamental Mode (FM) only [6].…”