We report an all-fiber mode-lock holmium-doped ring laser passively mode-locked by nonlinear polarization rotation without dispersion compensation. The laser produced picosecond pulses at 2.057 µm. The average output power was 4.5 mW.

We demonstrate an all-fiber 2 μm holmium-doped laser hybrid mode locked by the co-action of nonlinear polarization evolution and absorption saturation of single-walled carbon nanotubes. The laser was pumped by a continuous-wave ytterbium-doped fiber laser at a wavelength of 1125 nm. The holmium laser generated 1.4 ps soliton pulses at a wavelength of 2082 nm with bandwidth up to 3.3 nm and repetition rate of 14.9 MHz. An average output power of 4.7 mW was obtained corresponding to pulse energy up to 0.3 nJ and peak power of 220 W.

The spectrally flat supercontinuum generation in the wavelength range of 900–2400 nm is demonstrated in silica-based fibers of variable core diameter and dispersion. It is shown that, in comparison with standard optical fibers of the same length, supercontinuum spectra 200 nm wider can be realized in the samples under study. The significant difference between the spectral and temporal transformations of radiation depending on the direction of propagation is demonstrated in the researched fiber samples.

In this paper, we demonstrate the selection of radiation from the stimulated Raman scattered radiation, while using a spectral filter, based on a high-reflection fiber Bragg grating and an optical circulator. As a result, a stable pulsed signal was obtained at a wavelength of 1125 nm with a repetition rate of 1 MHz. The pulse duration and energy varied from 120 to 173 ps and 9 to 15 nJ, respectively, depending on the operating regimes of the master oscillator and amplifier.

We have demonstrated the amplification of the small signals in a spectral range of 2-2.15 um by all-fiber Ho-doped amplifier pumped at 1125 nm. Maximum gain more than 35 dB was achieved.

Absorption of continuous wave and pulsed resonance radiation at a wavelength of 1.6 μm at the upward transition from the excited state ⁵ I ₇ of holmium (Ho ³⁺ ) ions in silica-based fiber has been studied. Analysis of experimental and simulated data of the absorption dynamics for the case of pulsed pumping of Ho-doped fiber allowed us to determine the previously unknown value of the absorption cross-section at the transition ⁵ I ₇ → ⁵ I ₅ as 1.9×10 ^-21 cm ² . It allowed us to correctly simulate the relaxation process of the ⁵ I ₇ level population averaged over the fiber length in the presence of stationary resonance radiation. The effect of pulsed resonance radiation with different peak powers (10 and 100 W) and pulse duration of 1 μ s on the stationary active medium was considered. The mutual influence of the Ho-doped fiber characteristics and the resonance radiation at a wavelength of 1.6 μm was found. This allows the resonance radiation to be used as an attenuator or modulator of laser radiation at the ⁵ I ₈ → ⁵ I ₇ transition in Ho-doped fibers.