Aurélien Ricci

Energy-scalable temporal cleaning device for femtosecond laser pulses based on cross-polarized wave generation

We report on a compact energy-scalable device for generating high-fidelity femtosecond laser pulses based on spatial filtering through a hollow-core fiber followed by a nonlinear crystal for cross-polarized wave (XPW) generation. This versatile device is suited for temporal pulse cleaning over a wide range of input energies (from 0.1 to >10 mJ) and is successfully qualified on different ultrafast laser systems. Full characterization of the XPW output is presented. In particular, we demonstrate the generation of 1.6 mJ energy pulses starting from 11 mJ input pulse energy. The temporal contrast of the pulses is enhanced by more than 4 orders of magnitude. In addition, pulse shortening from 40 fs down to 15 fs Fourier-transform limit yields an overall peak-power transmission of up to 50%. This device not only serves as an integrated pulse contrast filter inside an ultrafast laser amplifier but also as a simple back-end solution for temporal post-compression of amplified pulses.

Grism compressor for carrier-envelope phase-stable millijoule-energy chirped pulse amplifier lasers featuring bulk material stretcher.

We demonstrate compression of amplified carrier-envelope phase (CEP)-stable laser pulses using paired transmission gratings and high-index prisms, or grisms, with chromatic dispersion matching that of a bulk material pulse stretcher. Grisms enable the use of larger bulk stretching factors and thereby higher energy pulses with lower B-integral in a compact amplifier design suitable for long-term CEP control.

Carrier-envelope-phase stable, high-contrast, double chirped-pulse-amplification laser system

We present the first carrier-envelope-phase stable chirped-pulse amplifier (CPA) featuring high temporal contrast for relativistic intensity laser-plasma interactions at 1 kHz repetition rate. The laser is based on a double-CPA architecture including cross-polarized wave (XPW) filtering technique and a high-energy grism-based compressor. The 8 mJ, 22 fs pulses feature 10⁻¹¹ temporal contrast at -20  ps and a carrier-envelope-phase drift of 240 mrad root mean square.

Generation of high-fidelity few-cycle pulses at 2.1 μm via cross-polarized wave generation.

We demonstrate the generation of temporally clean few-cycle pulses at 2.1 μm by shortening of 6-optical-cycle pulses via cross-polarized wave (XPW) generation in BaF(2), CaF(2) and CVD-Diamond crystals. By combining spectra and single-shot third-order intensity cross-correlation traces in a novel Bayesian pulse retrieval technique, we measured pulse durations of 20 fs, corresponding to 2.8 optical cycles. Our results show that XPW generation in the infrared could provide a high-fidelity source of few-cycle pulses for strong-field physics applications. It could also serve as an injector for high-peak power ultrafast mid-IR wavelength parametric amplifiers.

High efficient XPW generation for high contrast high energy ultrashort laser pulses

Cross polarized wave generation (XPW) is a well established technique for contrast enhancement of ultrashort pulses in high energy laser systems [1]. Efficient conversion with XPW only occurs at high intensities. Weaker, unconverted pre and post pulses are thus rejected by the second polarizer, thereby improving the temporal contrast of the pulse. XPW has several drawbacks especially in terms of simultaneously achieving high conversion efficiencies and output energies. Limitations in seeding the nonlinear filter with high energies arise from the upper intensity limit of white light generation while high conversion efficiencies require excellent beam quality.

Highly efficient hollow fiber compression scheme for generating multi-mJ, carrier-envelope phase stable, sub-5fs pulses

We present a simple technique for increasing the throughput of static hollow fiber compressors by up to 60%. By seeding the fiber with positively chirped, circularly polarized pulses, we obtain CEP-stable, 1.6mJ, sub-5fs pulses.

CARRIER-ENVELOPE PHASE PERFORMANCE OF HOLLOW-FIBER PULSE COMPRESSION FOR HIGH-ENERGY, SINGLE-CYCLE PULSE GENERATION

We investigate the performance and carrier-envelope phase (CEP) stability of hollow- fiber pulse compression for high-energy, close to single-cycle duration pulses. We find the onset of an ionization-induced CEP instability, which saturates above 1.25mJ.

Single attosecond pulses from plasma mirrors

We demonstrate for the first time the generation of isolated attosecond pulses from plasmas driven by few-cycle lightwaves with near-relativistic intensity. This is also the first experimental demonstration of the “attosecond lighthouse” effect.

High spatio-temporal quality, CEP-controlled, sub-10fs front-end light source based on XPW

Summary form only given. We present the current development of an injector for a high-contrast, ultrashort laser system devoted to relativistic laser-plasma interactions at kHz repetition rate [1]. The front-end is based on a 1 kHz, CEP-stabilized Ti:Sa CPA, delivering 1.4 mJ, 28 fs pulses, followed by a cross-polarized wave (XPW) filter for temporal cleaning and shortening. This filter is an optimized version of the waveguided XPW device described in [2]. 300 μJ pulses are routinely generated, corresponding to a XPW internal efficiency as high as 33% and a global energy transmission of 22%. As shown in Fig. 1(a), the XPW filter broadens and shapes the initial amplifier spectrum into a perfectly Gaussian spectrum with 110 nm FWHM, which supports sub-10 fs pulse duration (8.5 fs FTL) This corresponds to a 2.8 temporal pulse shortening factor. The significant spectral broadening and reshaping during XPW arise from the combination of high efficiency and optimized input spectral phase. Accurate characterization highlights the fidelity of the proposed injector. Despite the fact that the spectral broadening is due to nonlinear effects, short-term spectral stability is not degraded after XPW and remains below 2% rms across the entire spectrum (acquisition of 500 consecutive spectra). The long-term spectral stability was monitored by recording the spectrum at regular intervals over 90 min, showing only minor variations. We also measured the excellent spatial quality of the output beam, with a shot-to-shot beam pointing stability of 30 μrad (8 μrad rms). Furthermore, long-term energy stability is monitored continuously and is below 3% rms after the XPW stage. Finally, the measured CEP drift is 170 mrad rms (Fig. 1d). Although slightly higher than the amplifier (typically 110 mrad rms), this value confirms the robustness of the XPW filter. We also study the complex spatio-temporal dynamics of pulse shortening and spectral broadening during the XPW process. This intensity-dependent feature first affects the spectral homogeneity of the XPW beam (Fig. 1b). We highlight the role of self-phase modulation and self-focusing undergone by the fundamental beam and the mechanisms leading to spectral homogeneity of the XPW beam in the far-field (Fig. 1c). The experimental results are supported by 3D calculations. To conclude, our work shows that XPW can be configured to act as a robust pulse cleaning and shortening device, producing sub-10 fs pulses with exceptional spatio-temporal fidelity.

Generation of high-fidelity few-cycle pulses at 2 μm via XPW

We demonstrate the generation of spectrally clean few-cycle pulses at 2.1 μm by shortening of 40 fs pulses via cross-polarized wave (XPW) generation. Single-shot autocorrelation traces show 20 fs pulse duration.