Regina Gumenyuk

Dissipative dispersion-managed soliton 2 μm thulium/holmium fiber laser

We report a first dissipative dispersive-managed soliton fiber laser operating at 2 μm. The cavity comprised of all-anomalous-dispersion fiber employs chirped fiber Bragg grating, which ensures net-normal cavity dispersion and semiconductor saturable absorber for mode-locking.

Temporal control of vector soliton bunching by slow/fast saturable absorption

Saturable absorbers exhibiting complex dynamics are shown to provide efficient means for control of soliton interactions. This study, focused specifically on dynamics of vector soliton interactions, demonstrates that a soliton bunch can be efficiently compressed by attractive force generated in a saturable absorber. Effect of absorption recovery time on soliton bunching is explored by using fast and slow semiconductor and carbon nanotube absorbers.

Vector Soliton Bunching in Thulium-Holmium Fiber Laser Mode-Locked With PbS Quantum-Dot-Doped Glass Absorber

Saturable absorber based on PbS quantum-dot-doped glasses exhibiting bi-temporal recovery dynamics provides effective means for control of vector soliton bunching in 2-μm spectral range. The slow response of absorption creates an attractive force between pulses, and a bunch of tightly bounded vector solitons propagates in a cavity as an entity. Subjected to the joint action of attractive and repulsive forces, the solitons tend to oscillate within the bunch.

1.32 μm mode-locked bismuth-doped fiber laser operating in anomalous and normal dispersion regimes.

We demonstrate a 1.32 μm mode-locked bismuth fiber laser operating in both anomalous and normal dispersion regimes. In anomalous dispersion regime, achieved by using 13 nm/cm linearly chirped fiber Bragg grating, the laser exhibits multiple soliton operation with pulse duration of 2.51 ps. With the net normal cavity dispersion, the single-pulse operation with higher power has been obtained by avoiding the limitations generic to conservative soliton systems.

Impact of Gain Medium Dispersion on Stability of Soliton Bound States in Fiber Laser

Effect of the gain medium dispersion on stability of soliton groups in fiber laser has been studied. An attractive force produced by bi-temporal saturable absorber is used to enhance the soliton interaction and results in a firm bound state formation. It is found that active media supporting soliton formation causes irregular bunching in the fiber cavity, while the gain media with normal non-soliton dispersion demonstrates stationary bound state soliton generation. The results provide guidelines for the synthesis of an optimal dispersion map for soliton fiber lasers.

Dispersion compensation technologies for femtosecond fiber system

Developed highly chirped broadband fiber Bragg gratings and suspended-core fibers are shown to offer flexible dispersion management and allow for femtosecond oscillators with transform-limited pulse quality. Such dispersion compensators could have potential, particularly for all-fiber chirped-pulse amplification systems.

Multiple solitons grouping in fiber lasers by dispersion management and nonlinearity control

Dispersion-managed bound solitons and soliton bunches have been studied experimentally in a fiber laser mode-locked by saturable absorber with biexponential recovery dynamics, which enforces strongly the soliton interaction. The excessive nonlinearity and dispersion in a cavity was found to provoke the collapse of bound solitons states and induce the irregular soliton dynamics, which indicates the random relative phase variations between the solitons caused by the dispersive wave.

Tapered Fiber Bragg Gratings for Dispersion Compensation in Mode-Locked Yb-Doped Fiber Laser

We demonstrate a method for dispersion compensation based a on constant-period fiber Bragg grating imprinted into a tapered fiber (T-FBG). This technique is more convenient than the conventional approach based on chirped fiber Bragg gratings made using chirped phase masks. Using a uniform phase mask, the chirp and dispersion of the T-FBG is determined by the taper shape, and can be varied by changing the tapering parameters. We show that the T-FBG is capable of dispersion compensation of a few meter long fiber laser, resulting in soliton mode-locking.

Effect of absorption recovery in bismuth-doped silica glass at 1450 nm on soliton grouping in fiber laser

Saturable absorption in bismuth-doped glasses was found to have a noticeable influence on soliton interaction and group formation. This phenomenon, observed in 1450 nm mode-locked bismuth-doped fiber laser, shows the distinct feature of the multiple pulse regime, which appears as a stationary pulse group whose length can be spread over the whole cavity length by variation of the pump power and polarization. Pulse positioning within the ensemble depends on the saturation fluence and the relatively fast recovery dynamics of bismuth fiber.

Energy transition characterization of 1.18 and 1.3 μm bands of bismuth fiber by spectroscopy of the transient oscillations

The experimental evidence of laser transition type in bismuth-doped silica fibers operating at different spectral bands is presented. Spectrally resolved transient (relaxation) oscillations studied for a Bi-doped fiber laser at room and liquid-nitrogen temperatures allow to identify the three- and four-level energy bands. 1.18 μm short-wavelength band is found to be a three-level system at room temperature with highly populated terminal energy level of laser transition. The depopulation of ground level by cooling the fiber down to liquid-nitrogen temperature changes the transition to four-level type. Four-level energy transition distinguished at 1.32 μm exhibits the net gain at room temperature.