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International audience; We numerically show that when a gas filled hollow-core photonic crystal fiber is pumped by two-color pulses, an ultra-short pulse can be generated in the mid-infrared. This phenomenon is due to the cascaded nonlinear phenomenon starting from a spectral broadening of the two pulses combined with an induced phase-matched four wave-mixing lying in the midinfrared, with a dispersive wave. By selecting the mid-infrared band with a bandpass filter, we demonstrate the generation of 60 fs pulses at 3-4 µm and an ultra-short pulse duration of 20 fs can be reached with additional phase compensator.

International audience; We show numerically that ultra-short pulses can be generated in the mid-infrared when a gas filled hollow-core fiber is pumped by a fundamental pulse and its second harmonic. The generation process originates from a cascaded nonlinear phenomenon starting from a spectral broadening of the two pulses followed by an induced phase-matched four wave-mixing lying in the mid-infrared combined with a dispersive wave. By selecting this mid-infrared band with a spectral filter, we demonstrate the generation of ultra-short 60 fs pulses at a 3-4 mu m band and a pulse duration of 20 fs can be reached with an additional phase compensator

International audience; We report a tunable source that generates pulses in the infrared from an optical parametric amplification in a gas-filled hollow core capillary based on four-wave mixing process, in which the phase matching strongly depends on the gas pressure and the pump. In our case, we have generated pulses from 1 to 1.6 m in the sub-µJ level together with a parametric amplification in the visible.

International audience; Ultrashort pulses in the near-infrared (NIR) to mid-infrared (MIR) are widely used for laser matter interaction experiments, e.g. the relaxation process of carrier semiconductors and chemical dynamics at the femtosecond and attosecond time scale [1,2]. Many different approaches based on nonlinear processes or laser devices can be found to generate pulses in theses spectral ranges. Recently, four wave mixing (FWM) based parametric amplification in gas-filled hollow core capillary (HCC) has been used to create a tunable source of ultrashort pulses. For example, pulses can be generated in the visible with an energy at the 10 µJ level [4] and in the near infrared at ~1.4 µm with an energy of 5 µJ and a pulse duration of 45 fs [5]. Here, we present an implementation of a scheme to generate tuneable pulses from the NIR to the MIR toward a high-power level. The general principle of the FWM process relies on the combination of two pulses: a strong pump and a weak signal which co-propagate in a gas filled HCC. According to the phase matching condition, a part of the pump energy is transferred from the pump to the signal and an idler is created. In our experiment, this process was driven by pulses from a 1 kHz, Ti: Sapphire laser (800 nm, 120 fs) in combination with a weak continuum tunable from 420 to 650 nm (the signal) obtained by focusing a part of the 800nm laser into a 5 mm thick Sapphire plate. The relative delay between the pump and the seed pulses was controlled by a translation stage. Both beams were focused in a 30 cm long argon filled HCC with an inner core diameter of 150 µm. In parallel, we firstly achieved numerical simulations to predict the optimal pressure when the three waves propagate in the fundamental modes. From the computed total phase mismatch (Figure 1.a), we determine that tunable pulses in the near/mid infrared with high gain can be obtained from a pressure < 2 bar. Figure 1.b-c shows the experimental spectrum for a pressure of ~2 bar and an energy in the capillary of 146 µJ, when the pump pulse and the continuum signal are temporally overlapped. The tunability was obtained by changing the relative delay between the signal and the pump with the translation stage. In this condition, the idler is found to be tuneable from 1µm to 1.3 µm. Others simulations and experiments are in progress to extend the bandwidth toward the mid-infrared. a) b) c) Fig. 1 (a) Total phase mismatch in a Ar filled HCC. The core diameter is 150 µm. The pressure is tuned from 0.5 to 2 bar. The pump energy is 250 uJ.at 800nm b) Continuum spectrum (black line). Amplified spectrum for several delays, (color lines). c) Infrared spectrum generated by the FWM for a pressure of 2 bar. To summarize, we have shown that FWM based parametric amplification in gas filled hollow core capillary is an efficient method to generate tuneable pulses in the infrared band with a promising potentiality to reach the mid infrared. References [1] B.

International audience; Ultrashort pulses in the near-infrared (NIR) to mid-infrared (MIR) are widely used for laser matter interaction experiments, e.g. the relaxation process of carrier semiconductors and chemical dynamics at the femtosecond and attosecond time scale [1, 2]. Many different approaches based on nonlinear processes or laser devices can be found to generate pulses in theses spectral ranges. Recently, four wave mixing (FWM) based parametric amplification in gas-filled hollow core capillary (HCC) has been used to create a tunable source of ultrashort pulses. For example, pulses can be generated in the visible with an energy at the 10 µJ level [4] and in the near infrared at ~1.4 µm with an energy of 5 µJ and a pulse duration of 45 fs [5]. Here, we present an implementation of a scheme to generate tuneable pulses from the NIR to the MIR toward a high-power level. The general principle of the FWM process relies on the combination of two pulses: a strong pump and a weak signal which co-propagate in a gas filled HCC. According to the phase matching condition, a part of the pump energy is transferred from the pump to the signal and an idler is created. In our experiment, this process was driven by pulses from a 1 kHz, Ti: Sapphire laser (800 nm, 120 fs) in combination with a weak continuum tunable from 420 to 650 nm (the signal) obtained by focusing a part of the 800nm laser into a 5 mm thick Sapphire plate. The relative delay between the pump and the seed pulses was controlled by a translation stage. Both beams were focused in a 30 cm long argon filled HCC with an inner core diameter of 150 µm. In parallel, we firstly achieved numerical simulations to predict the optimal pressure when the three waves propagate in the fundamental modes. From the computed total phase mismatch (Figure 1.a), we determine that tunable pulses in the near/mid infrared with high gain can be obtained from a pressure < 2 bar. Figure 1.b-c shows the experimental spectrum for a pressure of ~2 bar and an energy in the capillary of 146 µJ, when the pump pulse and the continuum signal are temporally overlapped. The tunability was obtained by changing the relative delay between the signal and the pump with the translation stage. In this condition, the idler is found to be tuneable from 1µm to 1. To summarize, we have shown that FWM based parametric amplification in gas filled hollow core capillary is an efficient method to generate tuneable pulses in the infrared band with a promising potentiality to reach the mid infrared.

International audience; We investigate optical parametric amplification in a fiber pumped by a shaped pulse. The temporal structure of the pump impacts directly the instantaneous spectral gain and its temporal measurement is achieved in the spectral domain thanks to a chirped signal with a broad spectrum.

International audience; A tunable laser source (820-1200 nm) delivering ultra-short pulses in the range of 40-100 fs is investigated. It is based on the filtering of a continuum in the Fourier plane of a zero dispersion line without any phase compensator. The numerical simulations show the origin and the impact of the nonlinear chirp to guarantee ultra-short pulses.

We show a pulse characterization method for sub-cycle pulse measurements based on spectral shearing interferometry which allows measurement of undistorted sub-cycle self-compressed pulses in Kagome fiber with spectrum spanning 1.1-2.6 μm range.

International audience; 10 meter-long Kagome HC-PCF were used to deliver mJ Yb-laser pulses and 600 fs pulse-width in single-mode fashion. Self-compression to ~50fs, and intensity-level nearing petawatt/cm2 were achieved. Free focusing-optics laser-micromachining is demonstrated on different materials.

By stabilizing a single optical frequency comb tooth directly to the P(23) overtone transition of 12C2H2, and RF carrier-envelope offset frequency to GPS, we work towards an optically-referenced 89 MHz all fiber frequency comb.

International audience; We report on hypocycloid core shaped hollow-core Kagome fiber with a record loss of 70 dB/km at a spectral range of around 750-850 nm, which is compatible with Cs and Rb based applications. The fiber exhibits a single mode operation in a core diameter as large as $40~ \mu{\rm m}$ , and very low sensitivity to bend. We show experimentally that the bending-loss is limited by coupling between the guiding core mode and the modes in the cladding holes.

International audience; Gas-filled hollow optical fiber references based on the P(13) transition of the ν1+ν3 band of C122H2 promise portability with moderate accuracy and stability. Previous realizations are corrected (

We report high power operation of a Kagome-type HC-PCF at 1 μm. We demonstrate guidance of thin disk laser beam with powers in excess of 100 W in cw and 75 W in modelocked operation.

International audience; Milli-Joule energy and 600-femtosecond Yb-laser pulses were delivered in several meter Kagome hollow-core-photonic-crystal-fibers in robustly single-mode fashion. Self-compression to 50fs, and intensity-level of petawatt/cm2 were achieved. Free focusing-optics laser-micromachining is demonstrated.

International audience; We present two experiments confirming that hypocycloid Kagome-type hollow-core photonic crystal fibers (HC-PCFs) are excellent candidates for beam delivery of MW peak powers and pulse compression down to the sub-50 fs regime. We demonstrate temporal pulse compression of a 1030-nm Yb:YAG thin disk laser providing 860 fs, 1.9 µJ pulses at 3.9 MHz. Using a single-pass grating pulse compressor, we obtained a pulse duration of 48 fs (FWHM), a spectral bandwidth of 58 nm, and an average output power of 4.2 W with an overall power efficiency into the final polarized compressed pulse of 56%. The pulse energy was 1.1 µJ. This corresponds to a peak power of more than 10 MW and a compression factor of 18 taking into account the exact temporal pulse profile measured with a SHG FROG. The compressed pulses were close to the transform limit of 44 fs. Moreover, we present transmission of up to 97 µJ pulses at 10.5 ps through 10-cm long fiber, corresponding to more than twice the critical peak power for self-focusing in silica.

International audience; We report on numerical and experimental results on the influence of cladding ring number in hypocycloid-core Kagome HC-PCF. The number of rings has moderate effect on confinement loss whereas strong reduction in bend loss is demonstrated.

International audience; The development of hollow core photonic crystal fibers with low losses over a broad spectral region in the near IR enabled the demonstration of a novel laser type - Hollow-core Optical Fiber Gas Laser (HOFGLAS). The laser combines attractive features of fiber lasers such as compactness and long interaction length of pump and laser radiation with those of gas lasers such as the potential for high output power and narrow line width. This paper summarizes recent developments and describes the demonstration of C2H2 and HCN prototype lasers. Avenues to extend laser emission further into the IR are discussed.

International audience; We have now demonstrated and characterized gas-filled hollow-core fiber lasers based on population inversion from acetylene (12C2H2) and HCN gas contained within the core of a kagome-structured hollow-core photonic crystal fiber. The gases are optically pumped via first order rotational-vibrational overtones near 1.5 μm using 1-ns pulses from an optical parametric amplifier. Transitions from the pumped overtone modes to fundamental C-H stretching modes in both molecules create narrow-band laser emissions near 3 μm. High gain resulting from tight confinement of the pump and laser light together with the active gas permits us to operate these lasers in a single pass configuration, without the use of any external resonator structure. A delay between the emitted laser pulse and the incident pump pulse has been observed and is shown to vary with pump pulse energy and gas pressure. Furthermore, we have demonstrated lasing beyond 4 μm from CO and CO2 using silver-coated glass capillaries, since fused silica based fibers do not transmit in this spectral region and chalcogenide fibers are not yet readily available. Studies of the laser pulse energy as functions of the pump pulse energy and gas pressure were performed. Efficiencies reaching ~ 20% are observed for both acetylene and CO2.