Observation of soliton molecules with independently evolving phase in a mode-locked fiber laser.

We report the experimental generation of two-soliton molecules in an all-polarization-maintaining ytterbium-doped fiber laser operating in the normal dispersion regime. These molecules exhibit an independently evolving phase and are characterized by a regular spectral modulation pattern with a modulation depth of 80% measured as an averaged value. Moreover, the numerical modeling confirms that the limited modulation depth of the spectrum is caused by the evolution of the phase difference between the pulses.

Hysteresis of dissipative soliton molecules in mode-locked fiber lasers.

We numerically demonstrate bistability of a robust dissipative soliton molecule with independently evolving phase in a normal dispersion mode-locked fiber laser. It is shown that the separation of the peaks exhibits a hysteretic behavior as a function of the pump energy. Physically this corresponds to the coexistence of two bound-state branches, one with chaotic dynamics and another one with periodic dynamics. The crucial role of gain saturation for the appearance of the hysteresis is revealed. We observe the period-doubling route to chaos.

Analytical relation between effective mode field area and waveguide dispersion in microstructure fibers.

For optical fibers exhibiting a radially symmetric refractive index profile, there exists an analytical relation that connects waveguide dispersion and the Petermann-II mode field radius. We extend the usefulness of this relation to the nonradially symmetric case of microstructure fibers in the anomalous dispersion regime, yielding a simple relation between dispersion and effective mode field area. Assuming a Gaussian mode distribution, we derive a fundamental upper limit for the effective mode field area that is required to obtain a certain amount of anomalous waveguide dispersion. This relation is demonstrated to show excellent agreement for fiber designs suited for supercontinuum generation and soliton lasers in the near infrared.

Femtosecond Neodymium-doped microstructure fiber laser.

We demonstrate femtosecond operation of a Nd-doped mi-crostructure fiber laser. The fiber provides gain and anomalous dispersion at the lasing wavelength of 1.06 microm and enables the construction of short and simple cavity designs. The laser is passively mode-locked by the combined action of a saturable absorber mirror, fiber nonlinearity, and dispersion and produces transform limited sub-400-fs pulses with a pulse energy as high as 100 pJ.

Remote coupling in Bragg fibers.

We propose a remote directional coupler in Bragg fibers that allows for efficient conversion of the fundamental core mode into an annular mode structure over remote distances. We give design guidelines and confirm the results by finite-difference time-domain calculations.

Mode-locked Nd-doped microstructured fiber laser.

We demonstrate passive mode-locking of a microstructured fiber laser for the first time. The Nd-doped microstructured fiber exhibits a reduced dispersion at 1060 nm. A semiconductor saturable absorber mirror is used for passive mode-locking. Stable pulse formation with a pulse duration of about 26 ps and a pulse energy of 0.7 nJ is observed.