Dual noise-like pulse and soliton operation of a fiber ring cavity

Abstract

Passively mode-locked fiber lasers (PML-FLs) are versatile sources that are capable of generating a broad variety of short and ultrashort optical pulses. Besides conservative solitons, PML-FLs allow the generation of different kinds of dissipative structures, usually called dissipative solitons, a concept that also encompasses more complex structures and collective behaviors such as soliton molecules, gas, rain of solitons, etc. In addition to this, PML-FLs are also able to generate even more complex objects, the so-called noise-like pulses (NLPs). A few recent research results revealed a connection between NLPs and solitons, a sign that deterministic ingredients enter into the composition of NLPs, whose nature is traditionally assumed to be random. Although it is usual that a fiber laser is able to generate either solitons or noise-like pulses, depending on pump power and adjustments in the cavity, these two regimes are rarely observed simultaneously. In this paper, a PML-FL in a ring configuration is presented, in which it is possible to observe and verify experimentally the simultaneous presence of NLPs and solitons. Interestingly, these two components are found in different spectral regions, which greatly facilitates their separation and individual study and characterization.

Real-time temporal-spectral analysis of complex dynamics involving multiple soliton states in a dual-wavelength passively mode-locked fiber ring laser

“…An isolator was used to ensure unidirectional laser operation. The laser cavity also includes a polarizer, a quarter-wave retarder (λ/4), and a variable-wave retarder (VWR) to control the polarization [28]. The laser also has 10 m of twisted SMF-28 fiber, wrapped on a 50 cm diameter spool.…”

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

“…The complex envelope corresponds to the NLP and the low-intensity peaks correspond to the bunches of solitons. It is important to remark that the complete identification and characterization of this regime of NLP and bunches of solitons was presented in [29]. Besides, the pulse dynamics of this regime is analyzed in [36].…”

“…Other PML-FLs have a figure-eight or ring configuration; for these architectures, usually an artificial SA is used, which relies on non-linear effects generated in optical fiber, so indirectly the absorbed energy through to a laser component (commonly a polarizer or an isolator) is reduced by the changes that produces the non-linear effect. The Non-linear Optical Loop Mirror (NOLM) [6,25,26], the Non-linear Amplifying Loop Mirror (NALM) [28,35] or the Non-linear Polarization Rotation (NPR) [9,29] effect are examples of artificial SA implemented in PML-FLs. Commonly, the NPR effect is the SA meachanism used in a passively mode-locked fiber ring laser (PML-FRL); the latter is studied in this paper.…”

Experimental study of non-stationary operation of a dual-wavelength passively mode-locked fibre ring laser

“…Another peculiar regime is reached when repulsive interactions between the solitons leads to their uniform distribution in the cavity, which corresponds to harmonic mode locking [23,26]; in [27] a soliton rain dynamics has been reported, which is possible to trigger by injection of a continuous-wave in a PML-FRL; another behaviour that has been identified is a robust dissipative soliton called pulsating soliton [28]: in this kind of pulses the temporal envelope displays a periodic behaviour whose time scale is larger than the cavity period (with a periodicity corresponding to a double period, triple period, etc). On the other hand, a packet confining multiple solitons can be formed, known as bunch of solitons [29,30], this one commonly presents a single-peak envelope or multiple-peak envelope. It is important to remark that, due to the resolution and bandwidth limitations of the fast oscilloscope, the amplitude of the envelope depends on the distribution of the solitons in the bunch, in particular on their spacing: indeed, the envelope amplitude will represent the energy of single solitons only if their spacing is large enough; if they are closely packed, the envelope reproduces the energy of multiple solitons.…”

“…On the other hand, the spectral component centred at 1558 nm (red line) is characteristic of dissipative solitons as attested by the Kelly sidebands. The identification and detailed characterization of this NLP and bunches of solitons regime was performed in [30].…”