Dmitry Gaponov

High-power photonic-bandgap fiber laser

An original architecture of an active fiber allowing a nearly diffraction-limited beam to be produced is demonstrated. The active medium is a double-clad large-mode-area photonic-bandgap fiber consisting of a 10,000 ppm by weight Yb(3+)-doped core surrounded by an alternation of high- and low-index layers constituting a cylindrical photonic crystal. The periodic cladding allows the robust propagation of a approximately 200 microm(2) fundamental mode and efficiently discriminates against the high-order modes. The M(2) parameter was measured to be 1.17. A high-power cw laser was built exhibiting 80% slope efficiency above threshold. The robust propagation allows the fiber to be tightly bent. Weak incidence on the slope efficiency was observed with wounding radii as small as 6 cm.

Inner cladding microstructuration based on symmetry reduction for improvement of singlemode robustness in VLMA fiber

Very large mode area, active optical fibers with a low high order mode content in the actively doped core region were designed by removing the inner cladding symmetry. The relevance of the numerical approach is demonstrated here by the investigation of a standard air-silica Large Pitch Fiber, used as a reference. A detailed study of all-solid structures is also performed. Finally, we propose new kinds of geometry for 50 μm core, all-solid microstructured fibers enabling a robust singlemode laser emission from 400 nm to 2200 nm.

Management of the high-order mode content in large (40 μm) core photonic bandgap Bragg fiber laser

Very large-mode-area Yb(3+)-doped single-mode photonic bandgap (PBG) Bragg fiber oscillators are considered. The transverse hole-burning effect is numerically modeled, which helps properly design the PBG cladding and the Yb(3+)-doped region for the high-order mode content to be carefully controlled. A ratio of the Yb(3+)-doped region diameter to the overall core diameter of 40% allows for single-mode emission, even for small spool diameters of 15 cm. Such a fiber was manufactured and subsequently used as the core element of a cw oscillator. Very good beam quality parameter M(2)=1.12 and slope efficiency of 80% were measured. Insensitivity to bending, exemplified by the absence of temporal drift of the beam, was demonstrated for curvature diameter as small as 15 cm.

High-energy dissipative solitons generation from a large normal dispersion Er-fiber laser

We report on a passively mode-locked erbium-doped fiber laser featuring a large normal dispersion and emitting high-energy dissipative solitons. Mode-locking is stabilized by the combined actions of a high nonlinearity amplitude modulator and a narrow band spectral filter. The laser routinely delivers highly chirped pulses with more than 38 nJ energy that can be compressed down to 700 fs duration using bulk gratings. Numerical simulations confirm the experimental results and reveal the self-similar pulse evolution along the normal dispersion fibers included inside the cavity.

Microstructured fibres and applications

In this paper, we explore some new concepts of optical fibre designs exhibiting large active core surrounded by resonant cladding for high power delivery.

High-power passively mode-locked dissipative soliton fiber laser featuring cladding-pumped non-CVD thulium-doped fiber

We are reporting on the characterization of a thulium-doped fiber laser applying new powder technology in the mode-locking regime. A high average output power of 185 mW at a repetition rate of 9 MHz was achieved directly from the oscillator, which resulted in 21 nJ of pulse energy. The single-pulse operation regime was confirmed by careful numerical modeling of the laser cavity.

1.55-μm wavelength ultrafast fiber oscillators and amplifiers

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.

Cladding-pumped high-power mode-locked thulium laser based on fiber prepared by powder sinter technology

Recently, a considerable progress has been done on power and energy scaling of pulsed thulium doped fiber amplifiers working at l ~ 2 mm. However, obtaining a high average power directly at the oscillator output remains a real challenge mainly due to the anomalous waveguide dispersion at this wavelength range. Usually energy scaling of mode-locked oscillators is based on dissipative solitonic (DS) regime which requires normal net cavity dispersion. For l > 1.5 mm, one must use dispersion compensating elements inside the cavity to provide such an operating regime. Typically, pulse energy measured directly at the output of a passively mode-locked thulium fiber oscillator in net normal dispersion cavities is in order of few mW. In our contribution, we propose to use a cladding-pumped Tm-doped fiber combined with a net normal dispersion cavity enabling the generation of high average power, high energy picosecond pulses (185 mW, 21 nJ, 16 ps). The step-index double-clad Tm-doped fiber has been fabricated using one of the newest glass manufacturing technologies which has already demonstrated very good capabilities for the fabrication of efficient and homogeneous active material.

Photonic bandgap fibers for high-power CW and pulsed applications

In the reach for high-power large mode area (LMA) fibers are routinely used. Photonic bandgap fibers can be engineered so that a single mode can be propagated in a large core fiber. High-power CW or pulsed bandgap lasers can then be elaborated.

Optical Fiber Design And Fabrication: Discussion On Recent Developments

Level of emitted power and beam quality of singlemode fiber lasers have been drastically increased at the expense of loss due to bend sensitivity, simplicity of manufacturing and packaging. Furthermore, the extension of the spectral coverage was primarily explored by exploiting non‐linear effects, neglecting numerous possible transitions of rare earths. Through different research areas, we demonstrate the possibilities offered by new fiber designs and alternative methods of manufacturing. Photonic Band Gap fibers reconcile diffraction limited beam and large mode area with low bending loss. 80% slope efficiency is demonstrated together with a robust propagation allowing the fiber to be tightly bent until wounding radii as small as 6 cm. Highly ytterbium doped multimode core surrounded by high refractive index rods fiber exhibits a transverse singlemode behavior under continuous wave laser regime. A robust LP01 mode is observed and filtering effect is clearly observed. A non CVD process based on silica sand...