Principles of operation of a passively mode-locked fiber ring laser and 3D mapping of ultra-short pulses

Abstract

In this article, we study the operation and basic elements in a passively mode-locked fiber ring laser (PML-FRL), emphasizing the saturable absorber (SA) effect seen as a nonlinear filter in transmission, which is produced by the non-linear polarization rotation (NPR) and a linear polarizer. Besides, we employ a technique of 3D mapping measurements for characterizing ultra-short pulse dynamics.

Generation of burst pulses through multimodal interference in a passively mode-locked ytterbium fibre-ring laser

“…The SOP reaches the HWR, and consequently, it is transmitted in a certain percentage through the PM-ISO. The mode-locking pulses are achieved on various round trips of the signal propagating within the cavity [23]. A mathematical equation can be written as:…”

Real-time characterization of regimes between continuous-wave operation and mode locking in an all-normal dispersion ytterbium-doped fiber ring laser

“…The data are then segmented into successive cavity periods, which are stacked to form a sequence along a new axis, labelled in terms of the roundtrip number. This yields a 3D (or 2D + color scale) mapping representation of the intensity profile evolution, which contains three axes: fast time (time restricted to a window corresponding to one cavity period T r ), round-trip number (or slow time) and intensity [31]. Because successive cavity periods are acquired in a single measurement (relying on a single trigger event), they all share the same temporal reference, and the consecutive traces are readily aligned to form a fluid sequence free of discontinuities, as they are uniformly separated by exactly one cavity round-trip time T r , which is the time after which each structure in the signal repeats itself on average [10].…”

Numerical study of the fibre dispersion contribution in the pulse propagation problem

“…ω 4 in equation ( 27) is solved numerically by the iterative step of equation (28). As a guide, see appendix B, considering the input parameters: number = 2 12 , twindow = 800 ps, T 0 = 1 ps, P 0 = 15.82 W, z f = 66525 km and Δz = 1 m. Thus, given the previous explanations, now it is clear that the spectral intensity profile driven by the individual contribution of the fourth-order dispersion remains constant over propagation, as depicted in figure 6(a). In contrast, the temporal intensity profile under the individual contribution of the fourth-order dispersion contribution undergoes a slight broadening, as shown after propagation over 10L D 4 = 66 525 km in figure 6(b).…”

“…Accordingly, the role of the dispersion contribution is highlighted in the propagation of optical solitons [1][2][3][4], the prediction of pulsating instabilities [5,6], the four-wave mixing process [3,6,7], the fibre components (e.g. couplers and fibre Bragg gratings) and fibre interferometric configurations [8,9], the optical fibre amplifiers [9,10], the generation of short and ultrashort pulses in mode-locked fibre lasers [9,[11][12][13], the supercontinuum generation process [3,[14][15][16][17], among others. Additionally, different versions of the NLSE that include the dispersion contribution (including high order dispersion), the Kerr effect and other nonlinear effects, can be used to model the picosecond and femtosecond pulse propagation in different types of fibres, such as standard SMF [3,16,17], twisted optical fibre [18] and microstructure fibre (highly nonlinear fibre arrangements such as photonic crystal fibre, photonic bandgap fibre and gas-filled hollow-core photonic crystal fibre) [6,9,14,15].…”