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Optical pulses at high repetition rates are generated using rational harmonic mode locking and saturable absorber made of graphene nanoparticles in a fiber laser. The pulse generation from the fiber laser is modeled by solving the Generalized Nonlinear Schrodinger Equation. The computation involved varying the various saturable absorption parameters, such as linear and nonlinear absorption coefficients. Experimentally stable pulse trains at 20 GHz and 50 GHz are generated with a pulse width of ∼ 2.7 ps. This result agrees with the simulation.

A 30-GHz pulse-train is generated using the rational harmonic mode-locking technique, experimentally, using a Mach–Zehnder Lithium Niobate modulator. The width of the pulses is then reduced from 5.8-ps to 1.9-ps by incorporating nonlinear polarization rotation. This phenomenon arises due to the very high nonlinear behavior of the photonic crystal fiber (PCF) added to the ring laser cavity. Numerically solving the Generalized Nonlinear Schrödinger Equation provided insights into the pulse evolution behavior. The relative polarization angle and length of the PCF were varied to study their effects on the pulse-width.

Fiber laser technology and related performance and maturity are surveyed with the perspectives of laser acceleration. Advantageous fiber attributes allow high efficiencies in energy-conversion and heat removal and superior performance in high repetition. Wide utilization in the industries has led to high reliability and cost effectiveness in fiber laser technology. With coherent combination of fiber amplifiers, average-power and peak-power levels are targeted for practical laser-driven plasma acceleration applications.

Recent developments in fiber lasers and nanomaterials have allowed the possibility of using laser wakefield acceleration (LWFA) as the source of low-energy electron radiation for endoscopic and intraoperative brachytherapy, a technique in which sources of radiation for cancer treatment are brought directly to the affected tissues, avoiding collateral damage to intervening tissues. To this end, the electron dynamics of LWFA is examined in the high-density regime. In the near-critical density regime, electrons are accelerated by the ponderomotive force followed by an electron sheath formation, resulting in a flow of bulk electrons. These low-energy electrons penetrate tissue to depths typically less than 1 mm. First a typical resonant laser pulse is used, followed by lower-intensity, longer-pulse schemes, which are more amenable to a fiber-laser application.

High power fiber lasers are gaining increasing shares in the laser material processing market due to their many advantages over gas and solid-state lasers. The design approaches for the typical architectures used in continuous emission fiber lasers are revised and the impact of the different choices on the specifications of the cavity components are analyzed. Then, some results on the fabrication of key components for an all-fiber setup, such as pump (PCs) and signal combiners (SCs), are reported. Finally, an example of a high power module, suitable for the development of an over 4 kW system is presented.

The impact of thermally-induced refractive index changes on the single-mode (SM) properties of large mode area (LMA) photonic crystal fibers are thoroughly investigated by means of a full-vector modal solver with integrated thermal model. Three photonic crystal fiber designs are taken into account, namely the 19-cell core fiber, the large-pitch fiber (LPF) and the distributed modal filtering (DMF) fiber, to assess the effects of the interplay between thermal effects and the high-order mode (HOM) suppression mechanisms exploited in order to obtain effectively SM guiding. The results have shown significant differences in the way the SM regime is changed by the increase of heat load, providing useful hints for the design of LMA fibers for high power lasers.

In this paper, we review our recent developments on ultrafast pulse generation in erbium-doped fiber laser systems operating in the 1550 nm wavelength range. This work concerns the generation of ultrafast pulses from dissipative soliton fiber lasers featuring resonant saturable absorber mirrors, as well as their amplification in highly efficient erbium-doped large-mode-area fibers. Different amplification schemes featuring all-fiber components are studied leading to the achievement of record pulse energy from a high repetition rate laser system.

In this paper, we summarize the fundamental properties and review the latest developments in high power ytterbium-doped fiber (YDF) lasers. The review is focused primarily on the main fiber laser configurations and the related cladding pumping issues. Special attention is placed on pump combination techniques and the parameters that affect the brightness enhancements observed in high power fiber lasers. The review also includes the major limitations imposed by fiber nonlinearities and other parasitic effects, such as optical damage, modal instabilities and photodarkening. The paper summarizes the power evolution in continuous-wave (CW) and pulsed YDF lasers and their impact on material processing and other industrial applications.

We study the interaction and merging of optical solitons in normal-dispersion fiber lasers within the framework of the cubic-quintic complex Ginzburg–Landau equation (CGLE). We start finding homogeneous analytic solutions to this equation that are used in numerical simulations to build interacting kinks that lead to the formation of stable solitons. We then study numerically the interaction and merging of these solitons and characterize this process using moments such as the energy and momentum along the fiber. We have found that the merging process occurs only for small enough values of the initial distance (that depends on the phase difference) between solitons, otherwise they repel each other monotonically. The structure of the merging process shows a double peaked energy burst and (depending on the phase difference) a gain and/or loss of momentum. Finally, we propose a fitting model for isolated solitons in order to find a suitable analytical representation for the attractive interaction law before their merging.

A novel thermal tuning technique of fiber Bragg gratings is proposed. With this technique, the thermal sensitivity of FBG can now be flexibly designed. The proposed technique is used in an erbium-doped fiber ring laser. A wavelength shift of 6.8 nm is obtained with a temperature change of only 20°C, which corresponds to a thermal sensitivity of 0.34 nm/°C. The 3 dB linewidth of the laser is less than 0.1 nm in the whole tuning range. The threshold and slope efficiency of the laser are 7.9 mW and 18.6%, respectively. The laser tuning has good linearity and good repeatability.

A broadband pulsed mid-infrared difference frequency generation (DFG) laser source based on MgO-doped congruent LiNbO₃ bulk is experimentally demonstrated, which employs a homemade pulsed ytterbium-doped ring fiber laser and a continuous wave erbium-doped ring fiber laser to act as seed sources. The experimental results indicate that the perfect phase match crystal temperature is about 74.5${}^{\circ }$C. The maximum spectrum bandwidth of idler is about 60 nm with suitable polarization states of fundamental lights. The central wavelength of idlers varies from 3293 nm to 3333 nm over the crystal temperature ranges of 70.4–76${}^{\circ }$C. A jump of central wavelength exists around crystal temperature of 72${}^{\circ }$C with variation of about 30 nm. The conversion efficiency of DFG can be tuned with the crystal temperature and polarization states of fundamental lights.

We report what is, to our knowledge, the first experimental observation of the ultrafast evolution dynamics from bound states (BSs) to single-pulse states (SPSs) by using the dispersive Fourier-transform (DFT) technique. The evolutions from three categories of initial BSs to SPSs are spectrally resolved in real time. Usually, accompanied by complex soliton–soliton interaction and competition, one of the two bound pulses weakens to disappearance, and the other one evolves into SPS. During the transition, the two bound pulses ordinarily depart away from each other with complex changes of relative phase. However, it is found that not all the evolutions are accompanied by the increase of temporal separation between two bound pulses. The obtained results would facilitate a deep understanding of complex dynamics in nonlinear systems and provide valuable data for further theoretical studies.

The complex Ginzburg–Landau equation is solved numerically and three types of pulsating pulses are obtained: plain pulsating, erupting, and creeping solitons. We discuss the main characteristics of these pulses and demonstrate the possibility of converting them into fixed-shape pulses under the influence of some higher-order effects.

The generation of mode-locking pulse train in Erbium-doped fiber laser (EDFL) cavity was demonstrated using Nickel Oxide (NiO) saturable absorber (SA). The NiO compound synthesized via sonochemical method was embedded into poly ethylene oxide (PEO) film through solution casting technique to fabricate the SA film device. A small piece of the SA film was sandwiched between two ferrules in the EDFL cavity. By adding 180m single mode fiber (SMF) in the ring cavity, a stable mode-locking pulse train operating at 1558nm with a repetition rate of 1.1MHz was achieved. At 197.5mW pump power, the proposed mode-locked EDFL has output power and pulse energy of 3.35mW and 3.36nJ, respectively. This study may well be the first demonstration of mode-locked EDFL using NiO-based SA. The result indicates that NiO is the promising material for ultrafast photonic applications.

Fiber laser technology and related performance and maturity are surveyed with the perspectives of laser acceleration. Advantageous fiber attributes allow high efficiencies in energy-conversion and heat removal and superior performance in high repetition. Wide utilization in the industries has led to high reliability and cost effectiveness in fiber laser technology. With coherent combination of fiber amplifiers, average-power and peak-power levels are targeted for practical laser-driven plasma acceleration applications.

Recent developments in fiber lasers and nanomaterials have allowed the possibility of using laser wakefield acceleration (LWFA) as the source of low-energy electron radiation for endoscopic and intraoperative brachytherapy, a technique in which sources of radiation for cancer treatment are brought directly to the affected tissues, avoiding collateral damage to intervening tissues. To this end, the electron dynamics of LWFA is examined in the high-density regime. In the near-critical density regime, electrons are accelerated by the ponderomotive force followed by an electron sheath formation, resulting in a flow of bulk electrons. These low-energy electrons penetrate tissue to depths typically less than 1 mm. First a typical resonant laser pulse is used, followed by lower-intensity, longer-pulse schemes, which are more amenable to a fiber-laser application.

Optical pulses at high repetition rates are generated using rational harmonic mode locking and saturable absorber made of graphene nanoparticles in a fiber laser. The pulse generation from the fiber laser is modeled by solving the Generalized Nonlinear Schrodinger Equation. The computation involved varying the various saturable absorption parameters, such as linear and nonlinear absorption coefficients. Experimentally stable pulse trains at 20 GHz and 50 GHz are generated with a pulse width of ∼ 2.7 ps. This result agrees with the simulation.

A 30-GHz pulse-train is generated using the rational harmonic mode-locking technique, experimentally, using a Mach–Zehnder Lithium Niobate modulator. The width of the pulses is then reduced from 5.8-ps to 1.9-ps by incorporating nonlinear polarization rotation. This phenomenon arises due to the very high nonlinear behavior of the photonic crystal fiber (PCF) added to the ring laser cavity. Numerically solving the Generalized Nonlinear Schrödinger Equation provided insights into the pulse evolution behavior. The relative polarization angle and length of the PCF were varied to study their effects on the pulse-width.