Bülend Ortaç

131 W 220 fs fiber laser system.

We report on an ytterbium-doped photonic-crystal-fiber-based chirped-pulse amplification system delivering 131 W average power 220 fs pulses at 1040 nm center wavelength in a diffraction-limited beam. The pulse repetition rate is 73 MHz, corresponding to a pulse energy of 1.8 microJ and a peak power as high as 8.2 MW.

Self-starting self-similar all-polarization maintaining Yb-doped fiber laser

We report on the generation of self-similar pulses from an self-starting saturable absorber mirror (SAM) based environmentally stable fiber laser comprising only polarization maintaining (PM) fibers. Pulse energies of 1 nJ at a repetition rate of 17 MHz were obtained, which could be externally compressed to an autocorrelation width of 280 fs.

Approaching microjoule-level pulse energy with mode-locked femtosecond fiber lasers.

We report on the generation of high-energy ultrashort pulses from a mode-locked Yb-doped large-mode-area fiber laser operating in the all-normal dispersion regime. The self-starting fiber laser emits 9 W of average output power at a pulse repetition rate of 9.7 MHz, corresponding to a pulse energy of 927 nJ. The laser produces positively chirped 8 ps output pulses, which are then compressed down to 711 fs. These compressed pulses exhibit megawatt-level peak powers. To our knowledge, this is the first time that a mode-locked fiber oscillator has generated femtosecond pulses with pulse energies approaching the microjoule level in combination with high average output power. Numerical simulations show excellent agreement with experimental results and reveal further scaling potential, which is discussed.

High-energy femtosecond Yb-doped dispersion compensation free fiber laser.

We report on a mode-locked high energy fiber laser operating in the dispersion compensation free regime. The sigma cavity is constructed with a saturable absorber mirror and short-length large-mode-area photonic crystal fiber. The laser generates positively-chirped pulses with an energy of 265 nJ at a repetition rate of 10.18 MHz in a stable and self-starting operation. The pulses are compressible down to 400 fs leading to a peak power of 500 kW. Numerical simulations accurately reflect the experimental results and reveal the mechanisms for self consistent intracavity pulse evolution. With this performance mode-locked fiber lasers can compete with state-of-the-art bulk femtosecond oscillators for the first time and pulse energy scaling beyond the muJ-level appears to be feasible.

On the study of pulse evolution in ultra-short pulse mode-locked fiber lasers by numerical simulations

In this contribution we highlight several aspects concerning the numerical simulation of ultra-short pulse mode-locked fiber lasers by a non-distributed model. We show that for fixed system parameters multiple attractors are accessible by different initial conditions especially in the transient region between different mode-locking regimes. The reduction of multiple attractors stabilizing from different quantum noise fields to a single solution by gain ramping is demonstrated. Based on this analysis and model, different regimes of mode-locking obtained by varying the intra-cavity dispersion and saturation energy of the gain fiber are revised and it is shown that a regime producing linearly chirped parabolic pulses known from self-similar evolution is embedded in the wave-breaking free mode-locking regime.

Generation of parabolic bound pulses from a Yb-fiber laser

We report the observation of self-similar propagation of bound-state pulses in an ytterbium-doped double-clad fiber laser. A bound state of two positively chirped parabolic pulses with 5.4 ps duration separated by 14.9 ps is obtained, with 1.7 nJ of energy per pulse. These pulses are extra-cavity compressed to 100 fs. For higher pumping power and a different setting of the intra-cavity polarization controllers, the laser generates a bound state of three chirped parabolic pulses with different time separations and more than 1.5 nJ energy per pulse. Perturbation of this bound state by decreasing pump power results in the generation of a single pulse and a two-pulse bound state both structures traveling at the same velocity along the cavity. A possible explanation of the zero relative speed by a particular phase relation of the bound states is discussed.

High average and peak power femtosecond large-pitch photonic-crystal-fiber laser

We report on the generation of high-average-power and high-peak-power ultrashort pulses from a mode-locked fiber laser operating in the all-normal-dispersion regime. As gain medium, a large-mode-area ytterbium-doped large-pitch photonic-crystal fiber is used. The self-starting fiber laser delivers 27 W of average power at 50.57 MHz repetition rate, resulting in 534 nJ of pulse energy. The laser produces positively chirped 2 ps output pulses, which are compressed down to sub-100 fs, leading to pulse peak powers as high as 3.2 MW.

Generation of bound states of three ultrashort pulses with a passively mode-locked high-power Yb-doped double-clad fiber laser

We report the generation of high-power ultrashort bound states of three pulses in an ytterbium-doped double-clad fiber laser. The laser is mode-locked through nonlinear polarization rotation technique in a unidirectional cavity configuration. A pair of diffraction grating is incorporated in the cavity to compensate for the normal dispersion of the fiber. The laser generates chirped bound states of three pulses with either equal or different time separations, with more than 500-pJ energy per pulse. These pulses are subsequently compressed to 100 fs with a compression factor of more than 40.

High-energy femtosecond Yb-doped fiber laser operating in the anomalous dispersion regime

In this contribution, we report the first experimental demonstration of passively mode-locked Yb-doped single-mode large-mode-area air-clad photonic crystal fiber laser.

90 W average power 100 μJ energy femtosecond fiber chirped-pulse amplification system

We report on an ytterbium-doped fiber based chirped-pulse amplification system delivering 100 microJ pulse energy at a repetition rate of 900 kHz, corresponding to an average power of 90 W. The emitted pulses are as short as 500 fs. To the best of our knowledge, this is the highest average power ever reported for high-energy femtosecond solid-state laser systems.