Ultrafast high power fiber laser systems

Fiber laser systems offer unique properties for the amplification of ultrashort pulses to high powers. Two approaches are discussed, the amplification of linearly chirped parabolic pulses and a fiber based chirped pulse amplification system. Using the first method, we succeeded to generate 17-W average power of linearly chirped parabolic pulses at 75 MHz repetition rate and diffraction-limited beam quality in a large-mode-area ytterbium-doped fiber amplifier. The recompression of these pulses with an efficiency of 60% resulted in 80-fs pulses with a peak power of 1.7 MW. Furthermore, we report on a diode-pumped ytterbium-doped double-clad fiber based chirped pulse amplification system delivering 220-fs pulses, at 1040 nm wavelength, 73 MHz repetition rate and up to 131 W average power, corresponding to a peak power of 8 MW. Key element is a diffraction grating compressor consisting of highly efficient transmission gratings in fused silica allowing the recompression at this high power. To cite this article: J. Limpert et al., C. R. Physique

Crack-free high-aspect ratio holes in glasses by top–down percussion drilling with infrared femtosecond laser GHz-bursts

We report novel results on top-down percussion drilling in different glasses with femtosecond laser GHz-bursts. Thanks to this particular regime of light – matter interaction, combining non-linear absorption and thermal cumulative effects, we obtained crack-free holes of aspect ratios exceeding 30 in sodalime and 70 in fused silica. The results are discussed in terms of inner wall morphology, aspect ratio and drilling speed

Double-track waveguides inside calcium fluoride crystals

Calcium Fluoride (CaF2) was selected owing to its cubic symmetry and excellent luminescence properties as a crystal of interest, and ultrafast laser inscription of in-bulk double-track waveguides was realized. The guiding properties of these waveguides in relation to the writing energy of the femtosecond pulse are presented. The modified double-track waveguides have been studied by systematic developments of beam propagation experiments and numerical simulations. Furthermore, an adapted model and concepts were engaged for the quantitative and qualitative characterization of the waveguides, particularly for the transmission loss measurements and the three-dimensional refractive index mappings of the modified zones. Additionally, polarization-dependent guiding was investigated.Initiative d'excellence de l'Université de Bordeau

Experimental and numerical study of a monolithic single-oscillator thulium-doped fiber laser in continuous-wave regime

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Laser action along and near the optic axis of a holmium-doped KY(WO 4 ) 2 crystal

International audienceWe demonstrate the first (to our knowledge) quasi-three-level conical refraction laser operating at 2 μm, with 1.6 W of output power at 2074 nm, using a holmium-doped KY…WO 4 † 2 crystal. A maximum slope efficiency of 52% has been achieved, along the optic axis with respect to the absorbed pump power. Furthermore, lasing operation around the optic axis has been performed. In this case, a maximum output power of 3 W has been reached, with a slope efficiency better than 70%, which are the best performances ever reported on this material. Studies of conical refraction (CR) have recently revived. When a Gaussian light beam propagates along the optic axis of a biaxial crystal, under certain conditions a two ring-shaped beam can be observed, at the exit face of the crystal. Several publications describe this effect, theo-retically and experimentally [1–4]. Recent availability of long biaxial crystals, with good optical quality, facili-tates CR studies. Therefore, several applications of this effect have recently been investigated, such as optical tweezers [5], particle trapping [6], beam shaping [7–11], and microscopy [12]. There are also some publications about laser operation along an optic axis of a biaxial crys-tal, the first publication being [13]. Using a short (3 mm long) biaxial crystal of a CR-cut ytterbium-doped KGd…WO 4 † 2 (KGW), the output polarization of their laser was modified, by translating the output coupler mirror. The researchers obtained a slope efficiency of 60% along the CR axis, which is similar to the value obtained for a classical N g -cut orientation. However, the threshold was 2× higher for CR orientation. A few years later, [14,15] presented a four-level conical refraction laser, made with neodymium-doped KGW. The researchers obtained both a Gaussian and CR output beam. They reported a slope efficiency close to the quantum defect limit [14], and no influence of any thermal effect over the measurement range (up to 3 W at 1067 nm) was observed. The thermo-optic properties of neodymium-doped KGW were studied in [16]. The researchers show the anisotropy of the thermo-optic properties, along this propagation direc-tion with a short crystal (1 mm long). However, the effect of CR inside the cavity, changing the light distribution in-side the crystal, is still not well-known. In this Letter, we report the first experimental results (to our knowledge) of a holmium-doped KY…WO 4 † 2 (KYW) CR laser, showing laser action along the CR axis. Measurements near the optic axis have also been per-formed, in order to be able to compare CR and Gaussian beam intracavity laser performance

Comparative Study of Percussion Drilling in Glasses with a Femtosecond Laser in Single Pulse, MHz-Burst, and GHz-Burst Regimes and Optimization of the Hole Aspect Ratio

In this contribution, we present a comparative study on top-down drilling in sodalime glass, with a femtosecond laser operating in single-pulse, MHz-burst and GHz-burst modes, respectively. We investigate the hole depth, drilling rate, and hole morphology for these three regimes while keeping the same experimental conditions. We demonstrate that, for both burst regimes, the burst length has to be adapted for optimizing the hole depth. In the GHz-burst regime, the lower the ablation rate the longer the holes. The three drilling regimes lead to different hole morphologies, where the GHz-burst mode results in the best hole quality featuring glossy inner walls and an almost cylindrical morphology. Furthermore, we obtain crack-free holes, the deepest measuring 3.7 mm in length and 25 µm in entrance diameter corresponding to an aspect ratio of 150, which is the highest aspect ratio reported thus far with femtosecond GHz-burst drilling to the best of our knowledge

Bessel Beam Dielectrics Cutting with Femtosecond Laser in GHz-Burst Mode

We report, for the first time to the best of our knowledge, Bessel beam dielectrics cutting with a femtosecond laser in GHz-burst mode. The non-diffractive beam shaping is based on the use of an axicon and allows for cutting glasses up to 1 mm thickness with an excellent cutting quality. Moreover, we present a comparison of the cutting results with the state-of-the-art method, consisting of short MHz-bursts of femtosecond pulses. We further illustrate the influence of the laser beam parameters such as the burst energy and the pitch between consecutive Bessel beams on the machining quality of the cutting plane and provide process windows for both regimes

FBG reflected wavelength and fiber gain matching on a continuous wave monolithic Tm3+^{3+} , Ho3+^{3+} -doped fiber laser

International audienceWe present the optimization of a 2 µm CW monolithic single-oscillator laser in terms of output power and efficiency by the adaptation of the FBG reflected wavelength to the maximum gain wavelength of the fiber

Continuous Wave and Pulsed Modes of Operation of a High Power 2.09 µm Monolithic Single Oscillator Tm3+, Ho3+- Codoped Fiber Laser

International audienceWe report on a high power monolithic single-oscillator Tm 3+ , Ho 3+ -codoped polarization maintaining fiber laser emitting at 2.09 µm in Continuous Wave and pulsed modes of operation by Q-switching the laser cavity