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We report on an analysis of the nonlinear absorption in lithium triborate (LBO) used for second and third harmonic generation of ultrashort laser pulses at average powers in the order of kW and with sub-picosecond pulse duration. Thermographic imaging of the LBO crystals together with a simple analytical model revealed the presence of nonlinear absorption in both harmonic generation processes. Subsequent processing with a numerical model considering the nonlinear mixing, the absorption, and the heat conduction was used to estimate the absorption coefficients. Average powers exceeding 100 W in the ultraviolet and 400 W in the visible spectral range were obtained while maintaining a good beam quality by avoiding excessive nonlinear absorption.

Ultra-short pulse laser machining has been applied to the polishing of polycrystalline diamond (PCD) wafers in order to generate a smooth surface finish and reduce mechanical polishing time. Past studies were first carried out with a 5W laser highlighting the difference in ablation rates between PCD grades and the possible graphitization of diamond on the surface of micrometric PCD grades over a fluence threshold. Some upscaling work was undertaken at 80W with a 3-pulse burst reducing the Sa of a micrometric PCD grade lapped surface by 50% with a volume removal rate double that of the conventional mechanical polishing technique. From these previous base investigations, an ultra-short pulse laser delivering an average power of 1kW at 500fs via state-of-the-art thin disk multi-pass amplification is implemented here to achieve a higher ablation rate for high throughput processing. This is the first time that such an average power is applied on polycrystalline diamond in the ultra-short pulse regime. A burst mode is also implemented which is demonstrated to reduce the Sa by 10% and 55% on fine and coarse grade surfaces respectively compared to single pulse processing. From 80W to 1kW, the ablation rate is increased by a factor of 70 on micrometric PCD grades while the Sa of the initial lapped surface is reduced by 14% without any graphitization of the diamond structure. However, no improvement of the Sa is performed on the initial surface of coarser grades due to the formation of cavities (~5μm wide) potentially caused by the spallation of diamond grains.

We report on a kilowatt femtosecond laser with the high precision triggering function FemtoTrig® and flexible burst shapes. The high power femtosecond laser is based on a multi-stage hybrid fiber-crystal based Innoslab amplifier platform and chirped pulse amplification. The kilowatt femtosecond laser is foreseen to serve in high throughput applications integrating multiple beams generated by diffractive optical elements (DOEs) and allowing individual pulse control of the multiplexed beamlets via multi-channel acousto-optical modulators.

We report on kW femtosecond lasers that will enable large scale and high productivity industrial applications. Power scaling is achieved by an Innoslab amplifier followed by slab-based booster amplifier stages. The laser concept is capable to generate high pulse energies in the multi-mJ range as well as high pulse repetition rates in the MHz or GHz ranges. Moreover, free triggering (FemtoTrig®) and burst options as well as frequency conversion to the green and UV spectral region will leverage these femtosecond lasers into future industrial applications. Also in the scientific domain these lasers will have a strong impact, e.g. as pump sources for powerful OPAs or high harmonics generation at high photon flux.

In the present work, we investigate the benefits and the drawbacks in using on dual-wavelength double fs-pulse laser irradiation for fused silica processing. Our purpose of this pump-pump experiment is to tune the electron dynamics in order to optimize energy deposition and then to improve ablated volume. We use green wavelength (515 nm) for the first pulse to enhance photo-ionization and near-infrared (1030 nm) for the second pulse to maximize electron heating and impact ionization. The investigated parameters are pulse-to-pulse delay (up to 20 ps), second pulse duration (1 and 10 ps) and total fluence (up to 20 J/cm²). The results will be discussed in terms of ablated volume and optical transmission. We demonstrate that (i) there is an optimum delay and (ii) the ablation behavior is intermediate between green and near-infrared single pulse irradiation. Our results are supported by a numerical model taking into account electron dynamics and absorbed energy density.

Ultrafast laser glass processing is highly interesting for microelectronics and consumer electronics industries. Indeed, ultrafast laser technology has the unique capacity to produce a high-quality surface or bulk modification in dielectric transparent materials thank to nonlinear absorption. However, there is a need to improve both processing quality and throughput in order to meet the industry requirements. Beam shaping, performed by tuning spatial or temporal intensity profile, polarization, fluence, or any other laser parameters, is a smart and flexible technique to achieve this goal. This work is dealing with double fs-pulse laser irradiation of fused silica. Our purpose is to investigate the benefits and the drawbacks in using single and dual-wavelength double fs-pulse laser irradiation of fused silica. The influence of pulse-to-pulse delay (0 to 5 ps), pulse duration of the second pulse (1 ps to 25 ns) and fluence on both removal rate and optical transmission will be discussed.

Ultra-fast laser in micromachining have a reputation of highest precision and quality, which justifies additional invest in numerous applications. However, deficits in the synchronization of the positioning of beam deflection device and laser triggering -in particular at high repetition rates- still lead to defects like overtreatment due to the inertia of the mirrors of galvanometer scanners or path deviations at complex shapes. This in turn has led to an increasing demand of advanced pulse to pulse control for precise laser energy deposition. Two recent innovations have the potential to overcome these current limitations. Firstly, the scan ahead feature allows to calculate the actual beam position in acceleration and deceleration mode. According to the precise position feedback the control needs to adjust the repetition rate of the laser source e.g. at rectangular corners of a scan trajectory. Therefore, the pulse on demand feature at the laser interface is obligatory to dynamically adjust the pulse to pulse delay in order to accomplish constant energy deposition at any programmed scan pattern. We have put these two innovations to a test by combining an Excelliscan from Scanlab with an UV Tangor laser from Amplitude to validate the synchronization and constant pulse separation at various scan speeds and geometrical patterns. Applications trials like engraving with scan speed are presented in comparison to conventional scanning techniques to demonstrate the benefit of the fast synchronization and pulse on demand technologies.

Hybrid femtosecond lasers today deliver output powers of several hundred watts. Translating the available power into high-speed micromachining requires new approaches such as beam delivering tools with suitable synchronization of the laser pulses. We study the interest of rapid scanning systems or multi-beam shaping but also a rapid estimation of the ablation efficiency using a simple engineering model.

Translating the high available power for current industrial lasers in the 100 to 500 W range into high throughput micro-processing is of high importance for future industrial applications. High repetition rates and/or high energies can lead to detrimental thermal effects on the sample and degrade the process quality even using ultrafast lasers. New processing strategies are therefore required to take full advantage of the laser available power. Programmable spatial light modulators (SLM) can bring flexibility while maintaining a high spatial resolution compatible with complex optical functions like multi spots or user defined beam profiles. They enable specific laser characteristics, that can change during the process. The recent technological progress in LCOS based systems, enables high optical transmission greater than 95 %, but also high average power handling up to at least 100 W of laser power. However, the dependence of SLM shaping performance on laser bandwidth places specific requirement when using ultrafast lasers. We will present phase map optimization strategies dedicated to specific industrial applications.

We report on high-quality high-throughput laser milling of silicon with a sub-ps laser delivering more than 1 kW of average laser power on the workpiece. In order to avoid heat accumulation effects, the processing strategy for high-quality laser milling was adapted to the available average power by using five-pulse bursts, a large beam diameter of 372 µm to limit the peak fluence per pulse to approximately 0.7 J / c m 2 , and a high feed rate of 24 m/s. As a result, smooth surfaces with a low roughness of S a ≤ 0.6 µ m were achieved up to the investigated milling depth of 313 µm while maintaining a high material removal rate of 230 m m 3 / min .

Micromachining with high repetition rate femtosecond lasers and galvo scanners shows some limitations in the pulses positioning accuracy due to the galvo mirrors acceleration. This is particularly evident during scan speed or direction changes, resulting in a poor quality and overtreatment e.g. in corners. Several scanning approaches have been proposed to tackle these issues like the so-called skywriting (SW) and the pulse-on-demand (POD) being the last limited to ns lasers, moderate pulse repetition rates and scan speeds. Recently, POD approach has been extended to femtosecond laser sources with high power and high repetition rate. Here, for the first time, we explored the huge potential in laser micromachining of femtosecond POD technology associated to a fast galvo scanner. We tested an innovative set-up allowing for precise laser triggering at the requested time and position for MHz repetition rate and scan speed as high as 20 m/s. The pulse position accuracy of the system has been estimated to be ≤ 1µm whilst performances have been evaluated in comparison to conventional scanning and SW. Finally, we report the results of an engraving test on stainless steel. The advantages of the approach we propose are clearly shown in terms of machining quality and precision with respect to conventional scanning and reduction of the processing time by ≈ 40% with respect to SW.

We report on a flexible ultrafast thin-disk laser system delivering sub-1ps pulses at 1kW of average power. To enable high-throughput material processing a fast modulation scheme based on polarization-multiplexing and a burst-mode operation were implemented.

We report on a kW-class ultrafast laser amplifier emitting sub-300 fs pulses with a pulse peak power exceeding 1 GW. It is based on the direct amplification of 260 fs pulses in a versatile thin-disk multipass amplifier which provides fast modulation of the amplified beam on the workpiece by the implementation of a novel and robust polarization multiplexing scheme for the seed beam that is launched into the amplifier. Furthermore, the laser can be operated in a single-pulse or burst mode with a variable number of pulses per burst. Second harmonic conversion of the amplified beam by means of a lithium triborate crystal additionally led to an output power of up to 282 W in the green spectral range.

Thanks to the combined use of chirped pulse amplification and high power amplifier media combination, the Tangor amplifier platform is able to deliver short pulse duration (500µJ) within a small footprint. In this work package, Amplitude Systemes had to scale up the laser design in order to produce up to 200W before compression for seeding an YbYAG amplifier. Amplitude has to confirm the possibility to compress the pulse under 500fs too.&nbsp

International audience; —We present a numerical and experimental analysis of a nonlinear architecture to overcome the gain bandwidth limitation in regenerative amplifiers. This technique is based on the optimization of dispersion and nonlinear effects during the amplification process to obtain broad-bandwidth pulses that can be compressed to short durations with high temporal quality. We demonstrate the advantage of this method to maintain an excellent temporal quality of pulses even at high levels of optical nonlinearity. The technique has been applied to regenerative amplifiers using Yb:YAG, Yb:KYW, and Yb:CALGO crystals as gain media. In all cases we achieved the shortest pulse duration ever obtained from regenerative amplifiers using the respective laser crystals. These results underline the benefits of this amplification technique with respect to current state of the art.

Ultrashort pulse lasers have been established as precise and universal tools for the micromachining of solid materials (cutting, texturing …). For these applications the quality of the cutting cross-section is important. The use of a Gaussian beam profile and linear polarization leads to tapered cutting sidewalls. It is possible to change the polarization orientation in order to machine a material for obtaining straight and vertical sidewalls. For this purpose a specific polarization converter was used. The transformation of the polarization distribution from linear to radial and azimuthal is done by a subwavelength, binary grating creating a π phase shift between the TE and TM transmitted waves. In this paper we report on investigations on the influence of laser polarization (radial, azimuthal, circular, linear) on the ablation characteristics of molybdenum and PZT using an Yb doped crystal laser (500 fs) and compare these results with previously published results.

Pico and femtosecond lasers present a growing interest for industrials applications such as surface structuring [1] or thin film selective ablation [2]. Indeed, they combine the unique capacity to process any type of material (dielectrics, semiconductors, metals) with an outstanding precision and a reduced affected zone. We report on results about surface engraving of metals (Al, Cu, Mo, Ni), semiconductor (Si) and polymer (PC) using a picosecond thin disk Yb:YAG-amplifier. The pulse duration of this source can be changed using two different configurations: direct amplification of a 34ps-oscillator on one hand, and 1ps-chirped pulse amplification (CPA) scheme on the other hand. The results obtained with this thin disk laser are compared to ones achieved with two commercial femtosecond lasers respectively based on Yb-doped crystals and fibers, and operating at similar output power levels (up to 15Watt).

International audience; Single crystals of Yb doped Li6Y(BO3)3 were obtained by Czochralski method. The first laser tests were encouraging. Different parameters have been investigated to improve cw-laser performances. Thermal properties but also ytterbium content, crystal thickness and pump polarisation are reported. The best crystal configuration was determined and led to high power cw-laser tests equal to 2 W output power.

International audience; 520fs, 2.3-mJ pulses are demonstrated in a Yb:YAG booster amplifier delivering peak powers up to 4.4GW. To avoid damage and nonlinear-effect issues, passive divided pulse amplification is studied for the first time for bulk-amplifier. Great efforts have been deployed in the development of laser systems delivering femtosecond pulses for industrial and scientific applications. Among all available technologies, fiber lasers came out as one of the best choice due to their capability to deliver short pulse duration (typically 300 to 500 fs) together with high average power within very reliable and robust systems. Nevertheless, one of the main drawbacks remains the limited output energy available for such laser due to the strong confinement of the light. Standard femtosecond fiber lasers can deliver typically up to 10s µJ energy pulses; and lasers based on rod type technology allow to reach up to the mJ level for laboratory systems [1-2] and 200 µJ for industrial systems. We propose here to enhance the energy from fiber sources by implementing a very simple, but optimized, Yb doped YAG booster stage. This booster consists in using a cm-long crystal to have a simple high gain booster together with a rather-modest length to prevent from deleterious nonlinear effects like self-phase modulation and critical self-focusing. Secondly, the use of a simple and passive divided pulse amplification (DPA) setup [3] is also investigated, in order to exceed the energy limitation. We investigate how the DPA permits to overcome the laser threshold limits from 2.9 mJ to 4.1 mJ. This simple and straightforward amplifier geometry allows to deliver, in a nominal and safe regime, ultrashort pulses below 520fs for energy of 3mJ (before compression) 2.3 mJ after. We demonstrated then pulses up to 4.4 GW of peak power. The fiber laser source used is a standard industrial laser-developed by Amplitude Systems-that delivers pulse energy 180µJ up to 100 kHz repetition rate with duration of 350 fs. By limiting output energy below 200µJ, nonlinear effects and damages threshold in the laser are safely avoid. The Yb:YAG booster is implemented between the fiber amplifier and the compressor

We report a diode-pumped high-repetition-rate chirped-pulse Yb:KGW regenerative amplifier delivering tens of microjoules pulse energy at repetition rates of up to 300 kHz. High repetition rates are obtained by using an acousto-optic modulator as switching element in the regenerative amplifier cavity. The output pulses were compressed down to 600 fs pulse duration. Even shorter pulses in the 100 fs range are obtained using an amplifier configuration without chirped pulse amplification.

International audience; Generation of sub-150-fs-level pulses has been obtained from an Yb-doped crystal-based regenerative amplifier by applying an innovative amplification scheme. This scheme is based on optimization of the linear and non-linear phase during the amplification process inside the regenerative amplifier cavity. This technique with Yb:KYW allows to achieve pulse durations from diode-pumped Yb-doped regenerative amplifiers that were up to now only accessible with more complex Ti:sapphire amplifiers. With this Yb-doped tungstate crystal used in regenerative amplifiers, 145 fs pulses centered at 1026 nm with a spectral bandwidth of 14 nm at 50 kHz for an average power of 1.6 W have been generated.

Generation of sub 100 fs pulse has been obtained in an Yb:CALGO regenerative amplifier using nonlinear effects. It exhibits 97fs pulses at 1047nm with up to 24µJ energy with a spectral bandwidth of 19nm.

Ultrashort pulse lasers with pulse duration on the level of 100 fs can be used for a variety of interesting applications that rely on multiphoton processes or ultrafast dynamics. Up to now, this field was reserved to Ti:sapphire-based laser systems that exhibit a quite complex laser architecture and relatively low laser efficiency. This may be an important reason why such applications could not yet penetrate into large scale industrial applications. We have realized an Yb-doped tungstate-based regenerative amplifier in innovative amplifier architecture. We succeeded to produce 106-fs-pulses at 70μJ and 140 fs at 40 μJ pulse energy, respectively. The average power is on the level of several Watts. The optimized management and exploitation of dispersive and nonlinear effects during the amplification process inside the regenerative amplifier cavity enabled the generation of such short pulses with excellent temporal quality and in an extremely simple and robust laser architecture that is well suited for industrial environments. Applying the same amplifier architecture to an Yb:YAG thin disk regenerative amplifier enabled the generation of pulses as short as 360-fs at high pulse energies exceeding 200 μJ and high average powers of more than 30 W.

International audience; We report on the first diode-pumped Yb∶CaGdAlO 4 regenerative amplifier in the sub-100-fs regime. It generates pulses at a central wavelength of 1047 nm with up to 24 μJ energy (after compression) at a repetition rate of 50 kHz. The measured pulse duration is 97 fs, with a spectral bandwidth of 19 nm. We describe in detail how non-linear effects are optimally used to compensate gain narrowing in order to overcome the 100 fs barrier. Many industrial applications, such as athermal microma-chining [1] or eye surgery, require efficient and compact laser systems delivering ultrashort pulse energies of several tens of microjoules. To reach this energy level, femtosecond systems rely on the well-known chirped pulse amplification (CPA) concept in which nonlinear effects are minimized by sufficient temporal stretching prior to amplification. In terms of gain medium, Nd:glass bulk amplifiers have progressively been replaced by ytterbium (Yb)-doped crystalline materials that are more suited to average power scaling. Among Yb-doped materials, Yb:YAG and Yb:tungstates currently hold a dominant position. The combination of satisfying thermal conductivity together with large and broad absorption and emission cross-sections has allowed their dissemination and a new generation of ultrashort industrial amplifiers. On the other hand, the lack of crystalline disorder, responsible for the good thermal properties, also prevents the generation of sub-100-fs pulses due to the restricted available gain bandwidth. Therefore, typical durations from Yb:tungstate amplifiers are in the range of 200–400 fs [2–5] while for Yb:YAG-based amplifiers, the obtained pulse widths are typically between 500 fs and 1 ps [6,7]. Several Yb-doped crystal hosts have been studied in the past decade, mostly to generate both high average powers and shorter pulses from ultrafast oscillators. However, this work only starts to be extended to large-optical bandwidth amplifiers, among others, Yb: SYS [8], and more recently Yb-doped fluorites Yb:CaF 2 [9–11]. The Yb:CALGO material stands out among gain media because it has the broadest emission cross-sections together with good thermal and mechanical properties [12–17]. Indeed, with a gain bandwidth of ∼60 nm spanning from 1010 to 1070 nm, it has already been used to generate sub-50-fs pulses from ultrafast oscillators. Its thermal conductivity of 6.3–6.9 W⋅K −1 for a 2%-doped matrix holds great promises with respect to average power scaling. In this Letter, we report on the first sub-100-fs regenerative amplifier based on an Yb-doped

This study reports the first diode-pumped Yb:CALGO regenerative amplifier. It generates pulses at 1050 nm with up-to-240-μJ energy (before compression), with pulse duration near 350-450 fs and with a 5 nm spectral bandwidth.

We demonstrate a simple way to generate ultra-short pulses from an Yb-doped-crystal regenerative amplifier compensating the gain narrowing by self-phase modulation. We successfully demonstrated this technique with Yb:KYW demonstrating 143 fs pulses.

In order to minimize thermal load to the workpiece pico- and femtosecond lasers gain an increasing market share in industrial applications such as surface structuring or thin film selective ablation. Due to nonlinear absorption they are capable to process any type of material (dielectrics, semiconductors, metals) and provide an outstanding quality suppressing heat affects on the workpiece. In this paper, we report on results about surface engraving of metals (Al, Cu, Mo, Ni), semiconductor (Si) and polymer (PC) using a picosecond thin disk Yb:YAG-amplifier, which could be used in the picosecond regime as well as in the femtosecond regime by simply changing the seed laser source. In the picosecond regime the oscillator pulses, ranging from 10 to 34ps, can be directly amplified which leads to a quite simple and efficient amplifier architecture. On the other hand, a broadband femtosecond oscillator and a CPA configuration can be used in order to obtain pulse duration down to 900fs. We compare these results to recently obtained achievements using commercial femtosecond lasers based on Yb-doped crystals and fibers and operating at comparable output power levels, up to 15Watt. Finally, we have considered etch rate and process efficiency for both ps- and fs-regimes as a function of average power, of fluence and of intensity.

We present an Yb-CALGO thin-disk laser in continuous regime. In a slightly multimode configuration we obtain up to 29.5W of average power, corresponding to a slope efficiency of 40% and an optical-to-optical efficiency of 32%. We then design a monomode cavity, and achieve 25W of average power. The tuning range of the laser emission was from 1018 to 1052nm. In a Q-switch regime, we obtain more than 1 mJ at 100 Hz repetition rate, and 4.5W at 10 kHz repetition rate.

Femtosecond lasers gain increasing interest because of the unique combination of ultrashort pulse duration and extreme high peak power on the GW-level. In consequence, the machining process is dominated by multiphoton processes making it essentially universal and almost any type of material can be machined with excellent precision and quality. In this paper we report on Yb-doped crystal based laser sources with ultra short pulse duration of a few 100 fs, high energies of several 100 µJ, and high average power of up to several 10 W.Femtosecond lasers gain increasing interest because of the unique combination of ultrashort pulse duration and extreme high peak power on the GW-level. In consequence, the machining process is dominated by multiphoton processes making it essentially universal and almost any type of material can be machined with excellent precision and quality. In this paper we report on Yb-doped crystal based laser sources with ultra short pulse duration of a few 100 fs, high energies of several 100 µJ, and high average power of up to several 10 W.

We report on results about surface engraving of metals and semiconductor using a ps thin disk Yb:YAG-amplifier, and fs Yb-doped crystal based laser, and a fiber laser. We show that the maximum ablation rate can therefore be increased by a factor of 1.5 to 2 when the pulse duration is reduced from 10 ps down to 500 fs .

We have realized high-power mJ-range Yb:YAG-based thin-disk regenerative amplifiers of different pulse duration from 850fs to 30ps. These sources have been used for a comparative study of material ablation and the various results are presented.

International audience; We present the first demonstration of an Yb:CALGO thin-disk laser. In a slightly multimode configuration we obtained up to 30 W of average power at a slope efficiency of 40% and an optical-to-optical efficiency of 32%. With a single-mode cavity, an average power of 25 W was achieved. A tuning range from 1018 to 1052nm could be demonstrated by inserting a prism into the cavity. In Q-switched regime, we obtained 1 mJ of pulse energy at a repetition rate of 100 Hz.

Industrial applications of ultrafast lasers, notably in the field of precision micro-machining, are rapidly increasing. The quality and flexibility of the interaction process are well established. However, in order to fulfil the productivity requirement of industrial processes, it is necessary to continuously increase the average power of ultrafast lasers.

Many industrial and scientific applications need ultra-short and energetic pulses. Diode-pumped systems based on ytterbium-doped crystals have a huge interest thanks to their good thermal and spectroscopic properties. Among them, Yb:CaF 2 , shows very promising results for short pulse generation, and its long fluorescence lifetime, 2.4 ms, indicates a high energy storage capacity. We present a diode-pumped regenerative amplifier based on an Yb:CaF 2 crystal optimized to produce short pulses for various repetition rates ranging from 100 Hz to 10 kHz. The experiment is performed with a 2.6-% Yb doped 5-mm-long CaF 2 crystal grown by using the Bridgman technique and used at Brewster angle. To optimize the injection pulse spectrum in terms of bandwidth and maximum gain, the seed pulses are generated by a broadband Yb:CALGO oscillator centered at 1043 nm with a FWHM bandwidth of 15 nm at a repetition rate of 27 MHz. The pulses are then stretched to 260 ps with a transmission grating. The shortest pulse duration generated is 178-fs, and the corresponding energy is 1.4 mJ before compression (620 μJ after), at a repetition rate of 500 Hz for 16 W of pump power. The bandwidth is 10 nm centered at 1040 nm. At 10 kHz repetition rate, 1.4 W of average power before compression is obtained, corresponding to an optical-optical efficiency of 10%. We also noticed that the pulse duration tends to increase above 1 kHz, reaching 400 fs at 10 kHz.

Ultrafast lasers present a growing interest for industrial applications such as surface structuring or thin film selective ablation. Indeed, they combine the unique capacity to process any type of material, such as dielectrics, semiconductors or metals, with an outstanding precision and a reduced affected zone. In this paper, we report on results about surface engraving of metals (Al, Cu, Mo, Ni), semiconductor (Si) and polymer (PC) using a picosecond thin disk Yb:YAG-amplifier, which could be used in the picosecond regime as well as in the femtosecond regime by simply changing the seed laser source. In the picosecond regime the oscillator pulses (34ps) can be directly amplified which leads to a quite simple and efficient amplifier architecture. On the other hand, a broadband femtosecond oscillator and a CPA configuration can be used in order to obtain pulse duration down to 900fs. The results obtained with this thin disk laser are compared to ones achieved with two commercial femtosecond lasers respectively based on Yb-doped crystals and fibers, and operating at similar output power levels (up to 15Watt). Finally, we have considered etch rate and process efficiency for both ps-and fs-regimes as a function of average power, of fluence and of intensity.Ultrafast lasers present a growing interest for industrial applications such as surface structuring or thin film selective ablation. Indeed, they combine the unique capacity to process any type of material, such as dielectrics, semiconductors or metals, with an outstanding precision and a reduced affected zone. In this paper, we report on results about surface engraving of metals (Al, Cu, Mo, Ni), semiconductor (Si) and polymer (PC) using a picosecond thin disk Yb:YAG-amplifier, which could be used in the picosecond regime as well as in the femtosecond regime by simply changing the seed laser source. In the picosecond regime the oscillator pulses (34ps) can be directly amplified which leads to a quite simple and efficient amplifier architecture. On the other hand, a broadband femtosecond oscillator and a CPA configuration can be used in order to obtain pulse duration down to 900fs. The results obtained with this thin disk laser are compared to ones achieved with two commercial femtosecond lasers respectiv...

We demonstrate femtosecond and picoseconds thin disk laser amplifiers based on Yb:YAG as gain material. We obtained a pulse duration of 1 ps in a chirped pulse amplification (CPA) scheme and a pulse duration of about 30 ps in a CPA-free amplifier configuration. Pumped by a max of 70W we obtained an average output power of 20W and pulse energies up to 500μJ.

We report on a diode-pumped regenerative amplifier based on Yb:CaF2 material, delivering pulses up to 1.8mJ pulse energy at a repetition rate of 100Hz. The crystal is pumped at the zero line at 978 nm with a 10W continuous wave (CW) fiber coupled laser diode. The pulses have a spectral bandwidth of 16nm centered at 1040 nm, which indicates a good potential for millijoule range sub 100fs pulse duration after compression. It is also a good candidate for seeding higher energy diode-pumped ytterbium lasers.

We report a diode-pumped regenerative amplifier based on Yb:CaF2 material delivering up to 1.8 mJ at 100 Hz. The pulses have a spectral bandwidth of 16nm, indicating a good potential for millijoule range sub 100 fs pulse duration.

International audience; Chirped Bragg Gratings (CBGs) recorded in photo-thermo-refractive (PTR) glass have been successfully used as ultrashort pulse stretchers and compressors in a variety of solid-state and fiber chirped pulse amplification (CPA) laser systems. Compared to traditional pairs of surface gratings, CBG-based stretchers and compressors offer significant advantage in compactness and robustness. They are insensitive to polarization, require virtually no alignment and can handle high average and peak power. At the current technology stage PTR-glass CBGs can provide up to 30 nm spectral bandwidth and up to 300 ps stretched pulse duration. In this paper we propose a concept of sectional CBGs, where multiple CBGs with different central wavelengths recorded in separate PTR-glass wafers are stacked and phased to form a single grating with effective thickness and bandwidth larger than each section. We present results of initial experiment in which pulses from a femtosecond oscillator centered at 1028 nm are stretched by a 32-mm thick CBG to about 160 ps and recompressed by a monolithic 32-mm CBG with 11 nm bandwidth and by a sectional CBG with two 16-mm thick sections each having ~ 5 nm bandwidth and offset central wavelengths: 1025.5 and 1031 nm. In both cases, compressed pulse duration of 350-400 fs, ~ 1.1 × transform-limit was obtained. These results allow CBG-based pulse stretchers and compressors with high stretch ratio and wide bandwidth to be constructed from multiple sections.

We report a diode-pumped regenerative amplifier based on Yb∶CaF 2 , delivering 1.8mJ pulses at 100 Hz with a spectral bandwidth of 16 nm, able to produce sub-100 fs pulse duration.

We demonstrate a diode-pumped Ytterbium ultrashort pulse laser amplifier, avoiding chirped pulse amplification, resulting in a simple and robust laser sources. The average power exceeds 10 W for repetition rates between 50 and 100 kHz.

We demonstrate an Ytterbium diode-pumped laser with >10 W average output power, pulse repetition rate up to 100 kHz, and pulse duration around one picosecond. This system does not use the chirped pulse amplification system, yet generates much shorter pulses than typical picosecond lasers. The amplified pulses are slightly chirped, and pulse duration after external compression was as short as 400 fs. The laser combines the advantages of a picosecond amplifier, i.e. no pulse stretcher and compressor, with ultra short pulse durations which makes the laser source extremely interesting for applications such as transparent or semiconductor materials processing.

We demonstrate a directly diode-pumped femtosecond regenerative amplifier with up to 2.5mJ pulse energy at a repetition rate of several kHz. Chirped pulse amplification is applied in order to eliminate non linear effects and to avoid damage of optical components during the amplification process. We use Ytterbium doped materials for femtosecond pulse amplification and high average power operation. The laser system is compact and robust source in order to answer the need of high energy and high average power for micro and nanomachining applications. Average power up to 15W at pulse repetition rates up to 100 kHz are also demonstrated with the same system. This wide operating range means that the laser can be used for many different processes.We demonstrate a directly diode-pumped femtosecond regenerative amplifier with up to 2.5mJ pulse energy at a repetition rate of several kHz. Chirped pulse amplification is applied in order to eliminate non linear effects and to avoid damage of optical components during the amplification process. We use Ytterbium doped materials for femtosecond pulse amplification and high average power operation. The laser system is compact and robust source in order to answer the need of high energy and high average power for micro and nanomachining applications. Average power up to 15W at pulse repetition rates up to 100 kHz are also demonstrated with the same system. This wide operating range means that the laser can be used for many different processes.

We demonstrate a directly diode-pumped Yb:KYW femtosecond chirped pulse laser amplifier with>1 mJ pulse energy and pulse repetition rates higher than 5 kHz. We extracted up to 1.8 mJ at a pulse repetition rate of 2 kHz and 1.5 mJ at a pulse repetition rate of 5 kHz. After a high efficiency grating compressor having >80% transmission, we measured a pulse duration of 480 fs. The M2 value was better than 1.2.We demonstrate a directly diode-pumped Yb:KYW femtosecond chirped pulse laser amplifier with>1 mJ pulse energy and pulse repetition rates higher than 5 kHz. We extracted up to 1.8 mJ at a pulse repetition rate of 2 kHz and 1.5 mJ at a pulse repetition rate of 5 kHz. After a high efficiency grating compressor having >80% transmission, we measured a pulse duration of 480 fs. The M2 value was better than 1.2.

International audience; We report for the first time pulsed laser operation of the Yb-doped Li6Y(BO3)3 (Yb-LYB) crystal in the nanosecond as well as in the femtosecond regime. Pulse durations as short as 355 fs have been obtained in passively mode-locked operation and pulse energies up to 140 μJ in Q-switched operation.

We demonstrate a directly diode-pumped Yb-doped high repetition rate ultrashort pulse laser amplifier. The chosen amplifier geometry allows for avoiding chirped pulse amplification which results in a simple and robust ultrashort pulse source that is well suited for industrial micro- and nanomachining applications. The laser system produces average powers on the 10-W-level for pulse repetition rates between 50 and 100 kHz. The pulse duration out of the amplifier is below 2 ps which is about one order of magnitude shorter than that of state-of-the-art picosecond amplifiers based on Nd:YVO. If wanted, the slightly chirped amplified picosecond pulses can be compressed down to about 500 fs pulse duration by using a compact and high efficiency transmission grating compressor.We demonstrate a directly diode-pumped Yb-doped high repetition rate ultrashort pulse laser amplifier. The chosen amplifier geometry allows for avoiding chirped pulse amplification which results in a simple and robust ultrashort pulse source that is well suited for industrial micro- and nanomachining applications. The laser system produces average powers on the 10-W-level for pulse repetition rates between 50 and 100 kHz. The pulse duration out of the amplifier is below 2 ps which is about one order of magnitude shorter than that of state-of-the-art picosecond amplifiers based on Nd:YVO. If wanted, the slightly chirped amplified picosecond pulses can be compressed down to about 500 fs pulse duration by using a compact and high efficiency transmission grating compressor.

We report a diode-pumped high repetition rate chirped-pulse Yb:KGW regenerative amplifier delivering tens of microjoules pulse energy at repetition rates of up to 300 kHz.