Third harmonic generation (THG) via intermodal phase matching in fibers provides a convenient way to generate ultraviolet (UV) wavelengths. In this study, we systematically compare three THG configurations based on 1089 nm pumping to demonstrate UV output characteristics and dependencies on pump parameters and microfiber layout: (i) narrow-band conversion using a single long microfiber, (ii) narrow-band conversion using cascaded short microfibers, and (iii) broad-band conversion with a Raman-broadening pump. In the narrow-band case using a relatively long silica microfiber (waist diameter 520 nm, waist length 6 mm), third harmonic at 363 nm is generated at 1.14 $\mu$W average power, making a notable record in similar works. With multiple short silica microfibers (waist diameter 520 nm, waist length 3 mm), the idea of cascading the interaction media to improve THG performance is experimentally tested; the results show that the crucial phase relation required for coherent overlap of third harmonic components is satisfactorily achieved, while signal enhancement is counteracted by serious losses in the system, indicating that efficient signal delivering is a key issue in fiber-based optical frequency conversions. With the broad-band pump including the specific 1089 nm wavelength, the intermodal phase matching model for THG is verified, and a non-destructive approach is suggested to check the waist diameter of a fabricated microfiber.

>To date, the vast majority of ultrafast laser applications require a stable,unvarying, mode-locked pulsed output. Meanwhile, each year, laser research groups report multitudes of original ultrafast dynamics accessible from relatively standard laser architectures. The richness and universality of ultrafast laser dynamics hinge on the diversity of multiple-pulse regimes combined with a large range of bifurcations. 1 Ultrafast light patterns can self-assemble in a laser cavity, leading,

We unveil a family of dissipative solitons with composite structure, consisting of a central body sandwiched between two sets of sidelobes. The strongest sidelobes allow for long-range interactions with other solitons, and their composite phase structure allows for the generation of soliton molecules on demand.

Tm-doped fiber amplifiers (TDFAs) are capable of generating a broadband emission spanning from 1600 nm to 2100 nm. This wavelength range is significant for important applications, such as eye-safe atmospheric propagation, spectroscopy, sensing, and material processing. Utilizing this broadband emission can enhance the capacity of the optical communication channels. However, for dense wavelength division multiplexing, along with broadband amplification, a flat gain is equally desirable. Achieving a flat spectral gain profile is challenging due to the wavelength-dependent parameters in the TDFA, including the gain and inversion. To address the challenge of achieving flat broadband gain, we propose a scheme referred to as a "gain- guided amplifier". By integrating and optimizing a passive gain-flattening filter within a dual-stage amplifier configuration, we report an ultra-flat broadband spectral gain from 1690 nm to 1986 nm. Furthermore, the parameters such as pump configuration, fiber length, and attenuation functions have been optimized to produce up to 30 dB gain having +/- 0.05 dB tilt along with a noise figure less than 5 dB. This is one of the broadest and flatter gains ever predicted fora TDFA, which can pave the way for next-generation optical communication networks.

We investigate the self-generation of optical rogue waves from a noise-like pulse (NLP) fiber laser using the nonlinear polarization evolution mechanism as a virtual saturable absorber. We demonstrate a significant enhancement of the rate of rogue wave generation when a higher-order saturable absorption nonlinearity is selected. Numerical simulations and theoretical analysis corroborate and elucidate the experimental observations, showing that a higher probability for the optical rogue wave generation is achieved by combining overdriven saturated absorption with NLP generation.

Dispersion engineering has been instrumental in promoting the generation of higher energy mode-locked pulses through intracavity pulse stretching. Such an approach, which involves extra-cavity compression, often struggles to produce bell-shaped pulses. An alternative approach to generate energetic and pedestal-free pulses directly from the laser oscillator is to use dissipative effects in the near absence of dispersive effects [1], [2], which is easily accessible within fiber lasers in the multi-ps pulse regime. Mode-locked lasers generating pulses with narrow optical spectrum and pulse duration above 10 ps are advantageous for numerous applications, from nonlinear wavelength conversion and spectroscopy to laser ranging [3], [4]. This motivates the development of compact, tunable fiber laser oscillators delivering adjustable picosecond pulses in the microjoule range. In this work, we tailor intracavity picosecond pulses through spectral filtering using the framework of the recently demonstrated energy-managed soliton laser concept [5]. The present dispersion-less energy-managed mode-locked fiber laser presents a remarkable flexibility and scalability in pulse energy and duration. This work combines numerical modeling with experimental validation, using standard telecom components in the 1.5 μm telecom window, and demonstrates the generation of mode-locked pulses of up to 0.34 μJ at a fundamental repetition rate of 1.9 MHz.

We present an all-anomalous mode-locked laser architecture combining a few-mode gain fiber with single-mode passive fibers. This hybrid fiber laser generates high-energy pulses whose features are controlled by an intracavity spectral filter. Using a 1.7-nm filter bandwidth, the laser delivers 2.5-ps pulses of 39-nJ energy and 15.6-kW peak power. Increasing the filter bandwidth to 12 nm, the laser delivers nearly Fourier-transform limited 230-fs soliton pulses with 2.1-nJ pulse energy and 9-kW peak power. These results validate the scalability and flexibility of the energy-managed soliton laser approach for generating high-energy dissipative solitons in the anomalous dispersion regime with adjustable duration.

As the need for compact, cost-effective, and reliable laser sources continues to rise, fiber lasers have gained widespread interest in science and technology. In recent years, passively mode-locked fiber lasers (PMLFLs) have emerged as pivotal tools for generating ultrashort pulses, propelling advancements across various domains including communication, manufacturing, medicine, defense, and security. Amongst the various types of lasing states supported by a PMFL, the emphasis in this review is on the noise-like pulses (NLP) and their potential applications in supercontinuum generation (SCG). Interestingly, the quasi-stationary operation of the NLP envelope containing numerous chaotic sub-pulses has facilitated relatively high energy and broad bandwidth compared to standard mode-locked laser pulses. Moreover, the NLP generation goes beyond a specific cavity arrangement, the nature of mode-locking or cavity dispersion. Therefore, through this review, the foremost aim is to report the differences in NLPs across various experimental settings reported so far and highlight the strategies beneficial for high-energy and broadband NLP development directly from a fiber oscillator. Secondly, the application of NLP as a seed laser is examined to stimulate SCG in different types of fibers, underlining the improved supercontinuum characteristics over the conventional ultrashort pulse pumping schemes. Finally, the benefit of NLP-seeded SCG for various bio-medical and industrial applications are highlighted, thanks to the broader and flatter continuum achievable through compact experimental settings.

Dispersion engineering has been instrumental in promoting, through intracavity pulse stretching, the generation of higher-energy mode-locked pulses. Such approach requires extra-cavity compression and struggles to deliver bell-shaped pulses. However, in the context of dissipative solitons, it is also possible to generate energetic, pedestal-free pulses in the quasi-absence of dispersive linear effects. We achieve the latter by tailoring picosecond pulses through spectral filtering, inspired by the recently reported energy-managed soliton laser architecture. The present dispersion-less energy-managed mode-locked fiber laser demonstrates remarkable flexibility in both pulse energy and duration. Its experimental validation, using standard telecom components in the telecom window, yields mode-locked pulses of up to at a repetition rate of 1.9 MHz. We introduce an additional energy scaling by incorporating a few-mode gain fiber to generate pulses featuring low spectral distortion.

The $1.5-\mu \mathrm{m}$ wavelength band is a low-loss region for SiO2, serving as a communication window for fiber optic networks and falling within the eye-safe range. Therefore, pulsed lasers operating at this wavelength play a significant role in applications such as ranging and fiber optic communication. In 2024, we introduced the concept of energy-managed solitons, which allows surpassing the conventional soliton energy in fiber lasers employing exclusively anomalous dispersion as well as featuring extended laser output flexibility [1], [2]. Whereas the original work employed a cavity architecture including a free-space optics section and multi-W pumping power [1], [2], the present work elucidates the pulse-energy scalability within a simple and compact all-fiber cavity structure under lower pumping power (100–200 mW).

We present a 2-μm all-fiber laser in which a highly chirped fiber Bragg grating (CFBG) sets the net cavity dispersion to -100.9 ps2. Within an energy-managed laser architecture, this large anomalous dispersion enables the mode-locking of energetic and narrow-band pulses featuring: 17.8 nJ energy, 15.2 ps duration, and 0.36 nm bandwidth. These results validate that mode-locked laser oscillators incorporating CFBGs can generate picosecond pulses in the 2-μm wavelength region and demonstrate that, when combined with energy management, simultaneous scaling of pulse duration and energy is achieved. Experimental observations are well reproduced by numerical simulations.

We investigate both analytically and numerically the optical resonant radiation of bright, dark, and Peregrine solitons in a phase-matched second-harmonic generation process, when they undergo a large temporal walk-off. By virtue of approximate analytical soliton solutions, we obtain simple yet universal formulas for their resonant radiation frequencies, all of which show a good agreement with numerical simulations. We unveil that the optical resonant radiation occurs solely when the second-harmonic component has a normal group-velocity dispersion, and the temporal walk-off tends to stabilize the soliton evolution, by reducing the resonant radiation even in the phase-matched regime. These findings have significantly generalized previous results and will shed more light on the mechanism behind the generation of dispersive waves in quadratic media.

Mode-locked lasers exhibit a rich diversity of nonlinear dynamics, often featuring the nontrivial coexistence of linear dispersive waves and coherent structures, especially in transient evolution involving multiple soliton pulses. The coexistence of solitons and an embedded dispersive wave background sets a challenge for characterizing and analyzing these transient dynamics. Here, we demonstrate the real-time full-field characterization of transient soliton dynamics in a mode-locked fiber laser using nonlinear Fourier transform (NFT) and high-bandwidth coherent homodyne detection, revealing new insights into the physics of optical soliton interactions within complex nonlinear systems. Such characterization includes the formation of multiple solitons amid wide relaxation oscillations, the switching of multiple solitons, and controlled soliton drifting with associated digital encoding. NFT proves its efficiency in separating and analyzing coherent structures among the dispersive wave radiation in fiber lasers. By implementation of the inverse NFT, the corresponding pure soliton distribution can be reconstructed. These findings shed new light on ultrafast transient dynamics in optics.

With the generic non-Hermitian Hatano-Nelson Hamiltonians in real space, we investigate both analytically and numerically a multitude of non-Hermitian skin effects in a two- or three-dimensional intertwined lattice. Exact skin-mode solutions in such high-dimensional lattices as well as their topological explanations are provided, when subjected to hybrid boundary conditions or certain types of fully open boundary conditions. Under fully open boundary conditions, we particularly demonstrate several unusual non-Hermitian skin modes in either a two- or three-dimensional lattice, including the edge skin modes that can condense simultaneously on two or more edges for a two-dimensional lattice and the corner skin modes that have a much higher state density than others for a three-dimensional lattice, neither of which are achievable under hybrid boundary conditions. We anticipate that these results may inspire and facilitate the experimental studies of high-dimensional non-Hermitian physics, given their potential to realizing non-Hermitian topological lasing.

We address the challenge of configuring a fiber laser cavity to enable efficient access to multi-pulse structures such as dissipative soliton molecules. We theoretically compare multi-pulsing routes in the parameter space of the laser. By using a two-dimensional parameter space, we experimentally demonstrate an important reduction in the laser pumping power required to form soliton molecules.

We report on multi-wavelength generation through simultaneous second-order and third-order nonlinear parametric (SRS) in silica fibers. The fiber system consists of a short standard step-index silica fiber and a microfiber tapered from it. When this system is pumped with a 130 ps laser at 1040 nm, multiple new wavelengths in the UV (340-370 nm) and green (507-547 nm) bands arise through fourwave mixing (FWM)/sum-frequency generation (SFG) from the pump and its Raman signals. The evolution of these wavelengths with pump power is demonstrated in detail. fibers.

Ultrafast fiber lasers constitute a flexible platform to investigate new solitary wave concepts. To surpass the low energy limitation of the conventional solitons generated in standard telecom fibers, successive breakthroughs have promoted the usage of an important frequency chirping within fiber oscillators. This lead to original solitary wave regimes such as stretched-pulse, all-normal-dispersion, and self-similar dynamics. We here revisit ultrafast fiber lasers built from standard optical fibers featuring solely anomalous dispersion. We propose a new cavity design enhancing key dissipative effects with contained frequency chirping and demonstrate the generation of high energy pulses in the few-picoseconds regime. The involved intracavity dynamics blends conventional and dissipative soliton features in an unseen way with low- and high-energy propagation regions, allowing an increased flexibility and novel scalability prospects. The authors revisit ultrafast fiber lasers with anomalous dispersion to propose a new laser design enhancing dissipative effects. Their approach yields high-energy few-picosecond pulses, blending soliton features for improved flexibility and scalability.

Stripe solitons (SSs), the special localized wavepackets exhibiting periodic modulations, are identified in condensed matter physics and nonlinear science. Here, giant-chirp and chirp-free SSs in all-fiber lasers are demonstrated composed of single-mode fiber and polarization-maintaining fiber. The chirp property of SSs depends on the cavity dispersion while the stripe period relies on the fiber birefringence. Theoretical and numerical results coincide with experimental findings, revealing that the filtering and frequency shift of two vector modes is governed by the mode coupling related to birefringence and the nonlinear coupling induced by the phase modulation, respectively, which disrupts their complementarity and ultimately leads to modulation of the overall spectrum. With the aid of the saturable absorption and cross-phase modulation effects, the multi-color pulses synergistically overlap, giving rise to the unique SSs. These results present a simple approach for generating chirp-controllable SSs in all-fiber lasers, which is crucial for applications in difference frequency generation and soliton physics. Giant-chirp and chirp-free stripe solitons are obtained in all-fiber lasers composed of single-mode and polarization-maintaining fibers. The cascaded mode coupling and interference between the two polarization components result in the periodically modulated spectra. The self- and cross-phase modulation effects shape the overall spectrum into the stripe structure while the saturable absorption effect forces the multi-color pulses into an overlapped state. image

The development of the connections between ultrafast laser dynamics and solitary waves concepts is presented, with an attempt to emphasize on important research milestones and conceptual advances. At various stages, the concepts of conventional and dissipative solitons are found to echo, oppose, or complement each other. The pivotal role of fiber lasers is highlighted, which multiplied the investigation of ultrafast laser dynamics since the 90s, and lead to the widespread usage of dissipative soliton concepts that were instrumental in understanding original dynamical regimes and related optical waveforms, such as the generation of bright solitons in the normal dispersion regime and the self-assembly of optical soliton molecules within laser cavities.