In this paper we study the pulse quality degradation of an Ytterbium-based fiber laser in which B-integral ranges from 5 to 20 rad. A tunable chirped-fiber-Bragg-grating stretcher is optimized in term of reflectivity and phase profiles thank to a multivariable optimization algorithm. Parabolic and Sech2 spectral profiles are both studied in order to evaluate their robustness to non-linear degradation. Phase and reflectivity optimization can provide insight to design tailored specific pulse stretchers for CPA systems.
We report on a 100-fs GHz burst laser with up to 100-W average output power. This laser is based on a Tangor femtosecond laser with GHz burst option followed by nonlinear pulse compression in a gas-filled hollow core Kagomé fiber. Combining pulse compression with hollow core fiber transport is an attractive extension for industrial femtosecond lasers. Laser ablation of metals, silicon, and sapphire have been performed with this new laser source in order to study the impact of the ultrashort pulse duration on the laser matter interaction with GHz bursts.
We report on several ultra-short pulse compression schemes based on hollow-core photonic crystal fiber filled with a chosen gas-phase medium and undertaken in a versatile module coined “FastLas”. The scheme relies on dispersion management by both fiber design and gas pressure management to offer a highly versatile pulse compressor. Furthermore, the gas is also used to set the required optical nonlinearity. This type of hollow fiber based compressor is scalable with the laser wavelength, pulse energy and initial pulse-width. Among the achieved pulse compression, we list a self-compression of 500-600 fs ultra-short pulse Yb-laser and with energy range of 10-500 μJ. By simply scaling the fiber length we demonstrated pulses as short as ~20 fs for the whole energy range. Here, the self-compression is achieved through solitonic dynamic. Conversely, we demonstrated pulse compression based on self-phase modulation by adjusting the fiber and gas dispersion. Among the pulse compressors we have developed, based on self-phase modulation, we cite the compression of a frequency-tripled micro-Joule pulse-energy Yb-laser with a pulse width of 250 fs. The results show compressed UVpulses with temporal width in the range of 50-60 fs.
KEYWORDS: Pulsed laser operation, Beam delivery, Fiber lasers, Head, Cladding, Near field, High power lasers, Near field optics, Photonic crystal fibers, Laser systems engineering
We report on an ultra-low loss Hollow-Core Photonic Crystal Fiber (HC-PCF) beam delivery system (GLO-GreenBDS) for high power ultra-short pulse lasers operating in the green spectral range (including 515 nm and 532 nm). The GLOBDS- Green combines ease-of-use, high laser-coupling efficiency, robustness and industrial compatible cabling. It comprises a pre-aligned laser-injection head, a sheath-cable protected HC-PCF and a modular fiber-output head. It enables fiber-core gas loading and evacuation in a hermetic fashion. A 5 m long GLO-BDS were demonstrated for a green short pulse laser with a transmission coefficient larger than 80%, and a laser output profile close to single-mode (M2 <1.3).
We report on the design and fabrication of inhibited-coupling guiding hollow-core photonic crystal fiber with a transmission band optimized for low loss guidance around 2 μm. Two fibers design based on a Kagome-lattice cladding have been studied to demonstrate a minimum loss figure of 25 dB/km at 2 μm associated to an ultra-broad transmission band spanning from the visible to our detection limit of 3.4 μm. Such fibers could be an excellent tool to deliver and compress ultra-short pulse laser systems, especially for the emerging 2-3 μm spectral region.
The dramatic progress in power-scaling of ultra-short pulse (USP) lasers and their growing use in industrial applications call for flexible and robust beam delivery systems (BDS) over several meters with no temporal or modal distortions. Inhibited coupling (IC) hypocycloid Kagome hollow-core photonic crystal fiber (HC-PCF) has recently proved to be an excellent solution for guiding these USP. In order to reduce further the attenuation of such fiber and then to increase the BDS capabilities, we report on an optimized IC Kagome HC-PCF exhibiting record loss level (8.5dB/km at 1030nm) associated with a 225nm wide 3-dB bandwidth and low bend sensitivity.
We report on a Hollow Core-Photonic Crystal Fiber (HC-PCF) based high power ultra-short pulse laser beam delivery system (GLO-BDS) that combines ease-of-use, high laser-coupling efficiency, robustness and industrial compatible cabling. The GLO-BDS comprises a pre-aligned laser-injection head, a sheath cable protected HC-PCF and a modular fiber-output head. It enables fiber-core gas loading and evacuation in a hermetic fashion. 5 m long GLO-BDS were demonstrated for Yb USP laser, Ti:Sapphire laser and frequency-doubled Yb USP laser. They all exhibit a transmission coefficient larger than 80%, and a laser output profile close to single mode (M2 <1.3).
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