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Article Dans Une Revue Optics Letters Année : 2013

Sub-100-fs Yb:CALGO nonlinear regenerative amplifier

Résumé

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 In terms of gain medium, Nd:glass bulk amplifiers have progressively been replaced by ytterbium (Yb)-doped crystalline materials that are more suited to average power scaling.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
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Dates et versions

hal-01304260 , version 1 (19-04-2016)

Identifiants

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Julien Pouysegur, Martin Delaigue, Yoann Zaouter, Clemens Hönninger, Eric Mottay, et al.. Sub-100-fs Yb:CALGO nonlinear regenerative amplifier. Optics Letters, 2013, 38 (23), pp.5180-5183. ⟨10.1364/OL.38.005180⟩. ⟨hal-01304260⟩
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