Yoann Zaouter

High power ytterbium-doped rod-type three-level photonic crystal fiber laser

In this paper, we investigate power scalability of ytterbium-doped ultra large core photonic crystal fiber laser operating on the zero-line transition. We first report on an 80 microm core diameter ytterbium-doped rod-type photonic crystal fiber laser emitting up to 94 W in continuous wave regime when operating at 977 nm, which is to our knowledge the highest output power ever achieved from a single-mode solid-state laser operating at this wavelength. Key parameters of ytterbium-doped three-level laser, such as transparency pump intensity, pump absorption saturation, and gain competition between three and four-level laser operation are then discussed in the particular context of high power fiber laser operating at 977 nm.

Efficient diode-pumped Yb 3+ :Y 2 SiO 5 and Yb 3+ :Lu 2 SiO 5 high-power femtosecond laser operation

We report the mode-locked operation of two new Yb-doped oxyorthosilicates, Y2SiO5 (YSO) and Lu2SiO5 (LSO), that are longitudinally diode pumped. Yb:YSO supplied pulses as short as 122 fs with 410 mW of output power at 1041 nm. More than 2.6 W of average output power, for pulse durations of 198 fs at 1044 nm and 260 fs at 1059 nm for Yb:YSO and Yb:LSO, respectively, were provided. These are, to our best knowledge, the highest values ever obtained and the most efficient mode-locked laser in such a classic fiber-coupled diode-pumping configuration.

Coherent beam combining of two femtosecond fiber chirped-pulse amplifiers

We demonstrate coherent beam combining of two femtosecond fiber chirped-pulse amplifiers seeded by a common oscillator. Using a feedback loop based on an electro-optic phase modulator, an average power of 7.2 W before compression is obtained with a combining efficiency of 90%. The spatial and temporal qualities of the oscillator are retained, with a recombined pulse width of 325 fs. This experiment opens up a way to scale the peak/average power of ultrafast fiber sources.

Transform-limited 100 μJ, 340 MW pulses from a nonlinear-fiber chirped-pulse amplifier using a mismatched grating stretcher–compressor

We report on a compact double-stage ytterbium-doped-fiber chirped-pulse amplifier system delivering high temporal quality 270 fs pulses of 100 microJ energy at a repetition rate of 300 kHz resulting in a peak power of 340 MW. The recompression down to 1.1 times the Fourier limit is based on the exploitation of nonlinear phase shifts associated with mismatched stretcher-compressor units. A 1-m-long ytterbium-doped 80 mum core diameter photonic crystal fiber is implemented as the power amplifier and allows the production of 143 microJ pulses before compression with an accumulated B integral of 17 rad throughout the amplification stages.

Stretcher-free high energy nonlinear amplification of femtosecond pulses in rod-type fibers

We report on the study of direct amplification of femtosecond pulses in an 80 mum core diameter microstructured Yb-doped rod-type fiber amplifier in the nonlinear regime. The system includes a compact single grating compressor for the compensation of the small dispersion in the amplifier. With a 1250 line/mm (l/mm) grating-based compressor, pulses as short as 49 fs with 870 nJ pulse energy and 12 MW peak power are obtained. Alternatively, the use of a 1740 l/mm grating allows the production of higher quality pulses of 70 fs, 1.25 microJ pulse energy, and 16 MW peak power.

Continuous-wave and femtosecond laser operation of Yb:CaGdAlO4 under high-power diode pumping.

We demonstrate the generation of 68 fs secant hyperbolic pulses at a 105 MHz repetition rate with an average power of 520 mW from a diode-pumped Yb(3+):CaGdAlO(4) mode-locked laser. A semiconductor saturable absorber allows passive mode locking, and a 15 W diode laser is used to pump directly the crystal. To our knowledge this represents the highest average power ever obtained for a sub-100 fs diode-pumped Yb-bulk laser.

Femtosecond fiber chirped- and divided-pulse amplification system

We implement both chirped pulse amplification and divided pulse amplification in the same femtosecond fiber amplifier setup. This scheme allows an equivalent stretched pulse duration of 2.4 ns in a compact tabletop system. The generation of 77 W of compressed average power at 4.8 MHz, together with 320 fs and 430 μJ pulses at a repetition rate of 96 kHz, is demonstrated using a distributed mode-filtering, rod-type, ytterbium-doped fiber. Limitations in the temporal recombining efficiency due to gain saturation inside the fiber amplifier are identified.

High-order harmonic generation at a megahertz-level repetition rate directly driven by an ytterbium-doped-fiber chirped-pulse amplification system.

We report the first experimental demonstration (to our knowledge) of high-order harmonic generation in rare gases driven by a state-of-the-art high-power Yb-doped-fiber chirped-pulse amplification system. The fiber laser delivers 270 fs pulses in the 30-100 microJ energy range at repetition rates varying from 100 kHz to 1 MHz. A proper focalization allows reaching several 10(13) W/cm2 in a gas jet. We have been able to produce and detect harmonics up to order 31 (33.2 nm) in Ar at a 100 kHz repetition rate. High-order harmonic generation at 1 MHz is also demonstrated in Xe up to harmonic 15. The demonstrated extreme UV (XUV) source will bring ultrashort XUV coincidence experiments from synchrotron facilities to tabletop laboratories.

Generation of 63 fs 4.1 MW peak power pulses from a parabolic fiber amplifier operated beyond the gain bandwidth limit

We report the generation of 63 fs pulses of 290 nJ energy and 4.1 MW peak power at 1050 nm based on the use of a polarization-maintaining ytterbium-doped fiber parabolic amplification system. We demonstrate that operation of the amplifier beyond the gain bandwidth limit plays a key role on the sufficient recompressibility of the pulses in a standard grating pair compressor. This results from the accumulated asymmetric nonlinear spectral phase and the good overall third-order dispersion compensation in the system.

Yb:YAG single crystal fiber power amplifier for femtosecond sources

We demonstrate a versatile femtosecond power amplifier using a Yb:YAG single crystal fiber operating from 10 kHz to 10 MHz. For a total pump power of 75 W, up to 30 W is generated from the double-pass power amplifier. At a repetition rate of 10 kHz, an output energy of 1 mJ is obtained after recompression. In this configuration, the pulse duration is 380 fs, corresponding to a peak power of 2.2 GW. The M2 beam quality factor is better than 1.1 for investigated parameters.