Observations of four types of pulses in a fiber laser with large net-normal dispersion

Abstract

Four different types of pulses are experimentally obtained in one erbium-doped all-fiber laser with large net-normal dispersion. The proposed laser can deliver the rectangular-spectrum (RS), Gaussian-spectrum (GS), broadband-spectrum (BS), and noise-like pulses by appropriately adjusting the polarization states. These kinds of pulses have distinctly different characteristics. The RS pulses can easily be compressed to femtosecond level whereas the pulse energy is restricted by the trend of multi-pulse shaping with excessive pump. The GS and BS pulses always maintain the single-pulse operation with much higher pulse-energy and accumulate much more chirp. After launching the pulses into the photonic-crystal fiber, the supercontinuum can be generated with the bandwidth of >700 nm by the BS pulses and of ~400 nm by the GS pulses, whereas it can hardly be generated by the RS pulses. The physical mechanisms behind the continuum generation are qualitatively investigated relating to different operating regimes. This work could help to a deeper insight of the normal-dispersion pulses.

Chaotic chirped-pulse oscillators

“…This is not the only possible mechanism for chaotic destabilization of the CPOs. In a number of recent works, fiber lasers operating in net-normal dispersion regimes have demonstrated noise-like and multi-state behavior [5,6,8,9], that was attributed to saturation of the SAM. These systems operated well in the positive dispersion with relatively small TOD, and produced completely different signatures, such as nearly symmetric spectra and bell-shaped autocorrelation traces with a narrow coherence spike at the top, thus allowing clear distinguishing from the To characterize the chaotic regime, we reconstruct the phase-space portrait for the experimental CDS dynamics based on the standard lag-delayed procedure [ Fig.…”

“…On top of that, the higher-order dispersion is often unavoidable in broadband systems. As a result, the CPOs are described by a quite complicated multidimensional parameter space; on practice one can often encounter increased amplitude or spectral noise, period multiplication and modulational instability, noise-like and chaotic behaviour [3][4][5][6][7][8][9]. It is important therefore to establish the physical mechanisms, properties, and find practical rules to help recognising such regimes.…”

“…We demonstrate that the chaotic mode-locking in a solid-state oscillator results from a parametric resonance with dispersive waves, having different signature and mechanism than observed in the fiber lasers [5][6][7][8][9].…”

All-fiber ultrafast thulium-doped fiber ring laser with dissipative soliton and noise-like output in normal dispersion by single-wall carbon nanotubes

“…This indicates that the laser operates under the NL regime. 16,17 Results shown in Figure 3(c) suggest that a bunch of ultra-short pulses with randomly varying pulse width and peak power are generated within an envelope of over 300 ps. Figure 3(d) is the RF spectrum (measured by Agilent E4411B) of the NL pulses at the fundamental repetition rate; two wide side lobes and low signal to noise (SNR) are indicative of the inherent jittering of NL operation.…”

Delivering dispersion-managed soliton and Q-switched pulse in fiber laser based on graphene and nonlinear optical loop mirror

“…There are generally several ways to achieve passive Q-switching such as semiconductor saturable absorber mirrors (SESAMs) [6], carbon nanotubes (CNTs) [7] and graphene [8] and so on. To obtain passively mode-locked fiber laser, except for the methods mentioned above, nonlinear polarization rotation (NPR) [9], NOLM [10] and nonlinear amplifier loop mirror (NALM) [11] are exploited over past decades, too. Recently, MoS 2 and WS 2 are also used to Q-switching and mode-locking [12,13].…”