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

Abstract

Rare earth-doped fibres are a diode-pumped, solid-state laser architecture that is highly scalable in average power. The performance of pulsed fibre laser systems is restricted due to nonlinear effects. Hence, fibre designs that allow for very large mode areas at high average powers with diffraction-limited beam quality are of enormous interest. Ytterbium-doped, rod-type, large-pitch fibres (LPF) enable extreme fibre dimensions, i.e., effective single-mode fibres with mode sizes exceeding 100 times the wavelength of the guided radiation, by exploiting the novel concept of delocalisation of higher-order transverse modes. The non-resonant nature of the operating principle makes LPF suitable for high power extraction. This design allows for an unparalleled level of performance in pulsed fibre lasers.

Phase-stable, multi-µJ femtosecond pulses from a repetition-rate tunable Ti:Sa-oscillator-seeded Yb-fiber amplifier

“…After pre-amplification, reduction of the repetition rate and stretching to around 200 ps [19], the pulse train is stabilized to a pre-chosen carrier-envelopeoffset frequency f ceo by a feed-forward scheme using an AOFS (see text for details) using a CEP4 stabilization unit (Spectra-Physics, Femtolasers). The main amplification to 80 W is accomplished by two amplification steps in Yb-doped large-pitch fibers (LPF) [23] and two grating compressors. Subsequently, a rod-type LMA fiber and chirped mirrors are used to generate 0.7-µJ, ~30-fs pulses.…”

“…To minimize additional intensity and phase noise, the pulse picker is operated in synchronicity with the repetition rate as described in [19]. After phase stabilization by an acousto-optic frequency shifter (AOFS) operated in the feed-forward stabilization scheme [5], the subsequent amplification stages and the compression comprise two Yb-large-pitch-fiber (LPF) amplifiers [23], two grating compressors and a rod-type large-modearea (LMA) fiber for spectral broadening, followed by a chirped-mirror compressor.…”

A concept for multiterawatt fibre lasers based on coherent pulse stacking in passive cavities

“…Thus, to generate high pulse energies and, consequently, peak powers, fibres with large mode-field areas are employed. 12 Moreover, the technique of chirped-pulse amplification (CPA) is essential to stretch the laser pulses in time and, hence, reduce their peak power during amplification. 13 State-of-the-art grating-based stretchers lengthen femtosecond pulses up to several nanoseconds and have allowed fibre-based systems to produce pulse peak powers of up to 3.8 GW.…”

Rapid, electronically controllable transverse mode selection in a multimode fiber laser

“…Scaling core area in a fiber laser, whilst preserving the ability to select a single transverse mode (usually the fundamental mode), is a topic which continues to attract much interest within the laser community [1][2][3]. The need for larger mode areas to mitigate against damage and unwanted nonlinear loss processes in cladding-pumped fiber lasers, and allow scaling to higher output power has resulted in the development of a number of different schemes to achieve preferential lasing on the fundamental mode.…”