Ultrafast double-slab regenerative amplifier with combined gain spectra and intracavity dispersion compensation.

We report on a diode-pumped double-slab Yb:KYW regenerative amplifier with combined gain spectra and intracavity dispersion compensation. At repetition rates > 20 kHz an average power of up to 5 W after compression was generated, resulting in a maximum pulse energy of 250 µJ. Pulse durations of around 190 fs were achieved by using a GRISM compressor with a transmission efficiency of 90%.

Quantum-limited noise performance of a femtosecond all-fiber ytterbium laser.

We report on quantum-limited noise performance of a mode-locked ytterbium all-fiber laser. The laser operates at a high normal net dispersion without dispersion compensation. We show that the naïve application of analytical models to such lasers leads to strongly underestimated timing jitter, whereas a numerical simulation is in reasonable agreement with measurements. The measured timing phase noise is found to be essentially limited by quantum noise influences and not by technical noise. Furthermore we show that the phase noise of different comb lines has a quasi-fix point at the center of the optical spectrum and that the jitter is translated into high carrier-envelope offset phase noise with a linewidth of around 3 MHz.

Ultrafast high power Yb:KLuW regenerative amplifier.

We report on an high power ultra-short pulse regenerative Yb:KLuW amplifier based on the thin disk concept. A maximum pulse energy of 571 microJ was extracted at a repetition rate of 20 kHz. Compression of the output pulses resulted in a pulse duration of 197 fs assuming a deconvolution factor of 2.16. At a repetition rate of 125 kHz a maximum average power of 17.9 W was measured in front of the compressor.

Sub-100 fs pulses from a low repetition rate Yb-doped fiber laser.

We report on a passively mode-locked ytterbium-doped fiber laser with a repetition rate of 1.8 MHz. The laser was hybridly mode-locked via nonlinear polarization evolution and a semiconductor saturable absorber mirror. It generated chirped 3.8 ps long pulses with a pulse energy of 1.0 nJ which could be dechirped to a pulse duration of 93 fs.

Impact of third-order dispersion on the generation of wave-breaking free pulses in ultrafast fiber lasers.

Wave-breaking free pulses generated in passively mode-locked fiber lasers can tolerate a certain cubic phase delay induced by third-order dispersion without losing pulse quality. We demonstrate that the spectral as well as the temporal profile of the pulses become asymmetric. The generated pulses had a pulse energy up to 3.5nJ and could be externally compressed down to 145fs. The fact that the pulses could always be dechirped within 10% of the Fourier limit points out the linearity of the chirp. The pulse asymmetry was also observed in the output coupling characteristic of the mode-locking mechanism.

Similariton fiber laser with a hollow-core photonic bandgap fiber for dispersion control.

We report on an ytterbium-doped similariton fiber ring laser with a hollow-core photonic bandgap fiber for intracavity dispersion control. The oscillator is hybrid mode locked with a saturable Bragg reflector and by nonlinear polarization evolution. This scheme allows for an exact adjustment of the transmission characteristic to avoid the formation of bunched noiselike pulses while the self-starting characteristic is preserved. The oscillator generates highly stretched similaritons at 1025 nm with a pulse energy above 1n J at a repetition rate of 21.9 MHz.

Dynamics of parabolic pulses in an ultrafast fiber laser.

We report experimental and numerical results on the dynamics and propagation of parabolic pulses in a passively mode-locked ytterbium-doped fiber laser. Experimental data and numerical simulations are shown to match. Particular importance is attached to the pulse-shaping process in the different sections of the resonator. The paramount role of the gain fiber and saturable absorber in the laser is explicated.

Resonant nonlinearity in high-energy Er3+-fiber chirped-pulse-amplifiers.

We present experimental results, which show that the up-chirp of dispersively stretched femtosecond pulses decreases linearly with increasing pulse energy after amplification in Erbium-doped fibers. For 6 microJ output pulses a nonlinear dispersion of -410(6) fs(2) was measured. This nonlinear dispersive effect is attributable to the resonant dispersion of the Erbium-ions and the decrease of the inversion during pulse amplification and was about one order of magnitude larger than predicted by the literature. Most likely this deviation is attributable to the complex population dynamics of the Er3+-ions during pulse amplification, since in the literature the relation between the refractive index and Er3+-inversion was described for a quasi-static population distribution. Due to the high resonant dispersion the required compressor dispersion for minimum output pulse duration depends strongly on the output pulse energy in Erbium-doped fiber-based chirped-pulse-amplifier set-ups.

Novel suppression scheme for Brillouin scattering.

We demonstrate a new scheme for the efficient suppression of Brillouin scattering of a single-frequency laser source in a 72 m-long Neodymium-doped fiber amplifier by simultaneous amplification of two seed lasers separated in wavelength by two times the Brillouin-shift. This scheme can be independently employed in addition to conventional methods of suppressing stimulated Brillouin scattering enabling further power scaling of existing systems.

10 W widely tunable narrow linewidth double-clad fiber ring laser.

A highly efficient and widely tunable narrow linewidth ytterbiumdoped double-clad fiber laser with a linearly polarized output power of 10 W is demonstrated. The laser wavelength was tunable over a range of 24 THz from 1032 nm to 1124 nm by using a diffraction-grating pair in Littrow-Littman configuration in a unidirectional ring-cavity. The laser linewidth was smaller than 2.5 GHz for all power levels and all laser wavelengths. Additionally, an operating mode without any measurable amplified spontaneous emission with a linearly polarized output power of up to 3 W was realized.

Continuously tunable external-cavity diode laser with a double-grating arrangement.

A new external-cavity diode laser system based on an extended version of the Littman configuration is investigated. In our laser system the tuning mirror is replaced with a second grating mounted at the Littrow angle. This double-grating design provides a smaller passive bandwidth than the grating-mirror configuration, which is used to compensate for the large angle-of-incidence-dependent losses of the grazing-incidence grating. This results in a broader continuous tuning range with an improved mode stability. Because two laser diodes, emitting at 820 and 775 nm, respectively, are used, the external-cavity laser is continuously tunable without mode hops across 35 nm at 820 nm and 27 nm at 775 nm. Such a laser was used to measure the absorption lines of the oxygen A band around 762 nm. The complete R - and P -rotational branches of the b summation operator(g)(1) (+)(nu(??)=0)?X (3) summation operator(g)(-)(nu (?)=0) transition were recorded in a single-wavelength scan.