Search

Four-wave mixing is investigated when chirped pump and signal pulses are injected in a photonic crystal fiber. The shot-to-shot stability of the amplified coherent signal was measured by using the dispersive Fourier transform method and compared with numerical simulations. We highlight that the signal-to-noise ratio (SNR) of the pulsed signal increases with the injected power and show that it is not deteriorated through the amplification when the fiber optical parametric amplifier is strongly saturated. The SNR of the signal remains nearly constant after the amplifier.

Four wave mixing is investigated when chirped pump and signal pulses are injected in a photonic crystal fiber. The shot-to-shot stability of the amplified coherent signal was measured by using the dispersive Fourier transform method.

Four Wave Mixing band spectrogram has been retrieved from single shot spectra when a chirped pulse is injected in a fiber. This method leads to the seed chirp required for a large gain bandwidth.

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

This erratum reports corrections to the temporal axes in Figs. 12 and 13 of J. Opt. Soc. Am. B 39, 662 (2022)JOBPDE0740-322410.1364/JOSAB.444574.

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; Spectral correlation of four wave mixing has been investigated when a chirped pulse pump is injected in a photonic crystal fiber. The dispersive Fourier transform method was used to record single shot spectra and to measure the spectral correlation between the signal and idler components. We show that this method can determine the origin of the FWM in the pump spectrum.

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.

In this paper, we numerically and experimentally investigate the four-wave mixing process in a gas-filled hollow-core capillary in the femtosecond regime. The interaction between a visible broadband continuum and a chirped pump pulse resulted in the generation of a tunable near-infrared pulse of 1.2 to 1.5 µm and with the potential to reach the midinfrared range. Numerical simulations were performed in order to fully understand the role of key parameters such as the gas pressure, chirps, and relative delays of the involved pulses. The experimentation, which demonstrated and highlighted the feasibility of the tunable femtosecond source, led to the generation of an idler at 1.2 µm with a duration of ∼ 220 f s at the direct output of the capillary. The duration can ultimately be reduced to 45 fs in the presence of phase compensators.

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.

We report the spectral distribution of the parametric process generated in a photonic crystal fiber pumped by a chirped pulse. The spectral correlation of four-wave mixing has been measured using the dispersive Fourier transform method. From statistical analysis of multiple shot-to-shot spectral measurements, the spectral correlation between the signal and idler photons reveals physical insights into the particular portion of the pump spectrum responsible for generating the four-wave mixing. Therefore, the shape of the correlation map indicates directly the temporal and spectral links between the signal and the pump, which are highly important to design a four-wave mixing based amplifier.

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 review the use of hollow-core photonic crystal fibre (HC-PCF) for high power laser beam delivery. A comparison of bandgap HC-PCF with Kagome-lattice HC-PCF on the geometry, guidance mechanism, and optical properties shows that the Kagome-type HC-PCF is an ideal host for high power laser beam transportation because of its large core size, low attenuation, broadband transmission, single-mode guidance, low dispersion and the ultra-low optical overlap between the core-guided modes and the silica core-surround. The power handling capability of Kagome-type HC-PCF is further experimentally demonstrated by millijoule nanosecond laser spark ignition and ${\sim }100~\mathrm{\mu} \mathrm{J} $ sub-picosecond laser pulse transportation and compression.

The development of nonlinear fiber-endoscopes capable of imaging deeper in tissues and accessing internal organs represents a very attractive perspective for application of nonlinear optical microscopes to in-vivo research and diagnostics. The transmission of ultra-short laser pulses within a fiber is a critical issue in the development of such endoscopes. For instance, self-phase modulation (SPM), four-wave mixing (FWM) and Raman scattering occurring in conventional fibers severely affect transmitted pulses profiles in the time and frequency domains. Hollow-core (HC) fibers bring a solution to the problem, since propagation of the pulses in the air core limits nonlinear interactions. We employ here a novel double clad Kagome-lattice HC fiber for the delivery of ultrafast pulses across a large spectral window (~400nm) with no pulse distortion. The epi-collection of the signal generated at the sample is efficiently performed with a specially designed outer multimode cladding. The fiber is incorporated in a prototype endoscope using a four-quartered piezo-electric tube to scan the laser beam on the sample. The low numerical aperture of the hollow-core (0.02) is efficiently increased by means of a dielectric microsphere attached to the fiber face. This results in tight focusing (~1 micron) of the beam at the HC fiber output. Resonant scanning of the fiber tip allows imaging over a field of 300 microns using low driving voltages. High-resolution images with different contrast mechanisms, such as SHG and TPEF, acquired with the prototype endoscope illustrate the potential of these fibers for nonlinear imaging in regions otherwise inaccessible to conventional optical microscopes.

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.

Nonlinear self-compression of 1.7-µm pulses in a gas-filled Kagome fiber down to a single cycle duration and pulse energies up to 100 µJ provides a uniquely simple driver source for high-harmonic generation and above-threshold ionization experiments.

Over the past decade intense laser fields with a single-cycle duration and even shorter, subcycle multicolour field transients have been generated and applied to drive attosecond phenomena in strong-field physics. Because of their extensive bandwidth, single-cycle fields cannot be emitted or amplified by laser sources directly and, as a rule, are produced by external pulse compression—a combination of nonlinear optical spectral broadening followed up by dispersion compensation. Here we demonstrate a simple robust driver for high-field applications based on this Kagome fibre approach that ensures pulse self-compression down to the ultimate single-cycle limit and provides phase-controlled pulses with up to a 100 μJ energy level, depending on the filling gas, pressure and the waveguide length., Single-cycle and sub-cycle field transients are typically generated by external pulse compression where a combination of nonlinear broadening followed up by dispersion compensation is used. Here, Balciunas et al. use self-compression in a Kagome fibre to generate phase-controlled single-cycle pulses.

We report on numerical and experimental studies showing the influence of arc curvature on the confinement loss in hypocycloid-core Kagome hollow-core photonic crystal fiber. The results prove that with such a design the optical performances are strongly driven by the contour negative curvature of the core-cladding interface. They show that the increase in arc curvature results in a strong decrease in both the confinement loss and the optical power overlap between the core mode and the silica core-surround, including a modal content approaching true single-mode guidance. Fibers with enhanced negative curvature were then fabricated with a record loss-level of 17 dB/km at 1064 nm.

We demonstrate sub-cycle gigawatt peak power pulses self-compressed by optical shock waves in a simple manner based on gas-filled kagome hollow-core photonic crystal fiber.

We demonstrate a simple solution to a seemingly deadlocked problem of efficient nonlinear pulse compression designed to act on the whole beam, yield the ultimate single-cycle duration, and sustain pulse energy on the 100 µJ level which, given the single-cycle duration of the produced waveform, is immediately suited for a variety of challenges in high-field applications, including high-order harmonic generation.

Toward an all-fiber system, an erbium fiber laser-based comb is directly stabilized to a 12C2H2 transition at 1539.4 nm. The comb fractional instability at 1532.8 nm is 6×10−12 at 100 ms gate time.

Self-compressed single-cycle 1.7-µm with energies up to 100 µJ from a Kagome gas-filled waveguide are coupled into a high-harmonic-generation cell to efficiently produce coherent XUV below 60 eV in a uniquely simple setup.

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.

A single optical frequency comb line near 1532.83 nm from an 89 MHz all-fiber oscillator is amplified to perform saturated absorption spectroscopy inside a 12C 2 H 2 -filled hollow-core fiber. Noise introduced during optical comb amplification is discussed.

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.

We report on recent design and fabrication of Kagome type hollow-core photonic crystal fiber (HC-PCF) for the purpose of high power fast laser beam transportation. The fabricated seven-cell three-ring hypocycloid-shaped large core fiber exhibits an up-to-date lowest attenuation (among all Kagome fibers) of 40dB/km over a broadband transmission centered at 1500nm. We show that the large core size, low attenuation, broadband transmission, single modedness, low dispersion and relatively low banding loss makes it an ideal host for high power laser beam transportation. By filling the fiber with helium gas, a 74μJ, 850fs and 40kHz repetition rate ultra-short pulse at 1550nm has been faithfully delivered with little propagation pulse distortion. Compression of a 105μJ laser pulse from 850fs to 300fs has been achieved by operating the fiber in ambient air.

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.

Mid-IR lasers operating at 3–3.2 μm and 4.3–4.4 μm with efficiencies near 20% have been demonstrated from 12C 2 H 2 and HCN-filled low-loss (< 5 dB/m) kagome-structure HC-PCF and from CO-filled silver coated capillaries.

International audience; We report on hollow-core Kagome fiber with a record loss of 70dB/km and operating at ~800nm. We show experimentally that the bending-loss is limited by coupling between the guiding core mode and the modes in the cladding holes.

An analytical model has been developed to fully understand the concept of fiber optical parametric amplifiers pumped by broadband chirped pulses. Our model is in good agreement with the numerical resolution of the nonlinear Schrodinger equation and was used to tailor the gain bandwidth. In particular, we showed that the group delay difference between the pump and the signal can play a crucial role in the spectral extension of the gain. This exciting amplification concept should pave the way toward high gain ultrashort (

We report numerical investigations on ultrashort pulse amplification with high gain in a fiber-based optical parametric amplifier pumped by a broadband chirped pulse. The amplifier has been tailored for ultrabroadband amplification with an analytical model and has key features to overcome gain narrowing and pulse distortion, which are usually observed in ion-doped fiber amplifiers. By combining chirped pump and signal pulses in a fiber, we highlight the possibility to amplify sub-30-fs pulses with standard ultrafast technologies.

We compressed a high-energy SESAM-modelocked thin-disk laser using an Ar-filled Kagome-type HC-PCF: launching 41-µJ, 1.17-ps pulses directly from a 3-MHz oscillator, we obtain 179-fs pulses at 100-W of average power, reaching 80% overall compression efficiency.

We report on Kagome fiber based self-compression of 100 μJ IR pulses to single cycle duration and demonstrate HHG in an integrated scheme which allows a compact isolated attosecond XUV source implementation above 50 eV.

International audience; We report a detailed numerical study on the postcompression of high-energy (∼30 mJ) femtosecond laser pulses (∼40 fs), using the spectral broadening induced by optical-field ionization of a low-pressure helium gas in a capillary. Our numerical results are in very good agreement with previously published experimental data on spectral shapes, transmitted energies and recompressed pulse durations in the full range of laser energies and gas pressures investigated. Then, we calculate the performances of the method with shorter input pulses (∼20 fs) and demonstrate that few optical cycles recompressed pulses with 5 to 8.5 mJ energy could then be achieved.

International audience; An all-fiber based acetylene frequency reference is achieved with ~100 kHz accuracy. The three-cornered hat method was used to calibrate the stability of fiber-based frequency, and a 2×10-12 stability at 0.1 s is obtained.

A potentially portable optical metrology system is demonstrated by using an acetylene-filled optical fiber frequency reference as an optical reference to a fiber-laser based frequency comb without an intracavity EOM.