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attosecond pulse generation
The waveform-controlled few-cycle VIS/NIR laser drivers, available or under development, afford a wide range of opportunities for developing new sources and advancing existing sources of sub-fs to asec pulses. The near-single-cycle NIR light pulses that became recently available at MPQ from our FP-1, FP-2, and FP-3 sources, have pushed the frontiers of intense UV pulse generation to a few femtoseconds and of attosecond pulse generation below the 100-attosecond frontier. The state of the art is represented by isolated, near-nanojoule-energy, sub-100-as XUV pulses, produced at a carrier photon energy of about 80 eV with a flux of greater than 10^{11} photons/s, exceeding by several orders of magnitude the flux of any previous source of sub-fs light.
With our kHz few-cycle laser drivers, we pursue the generation of microjoule-scale near-1-fs to sub-fs pulses in the UV to the VUV (5-30 eV) range. These pulses, containing ultimately a single cycle of UV/VUV light, will be intense enough to trigger electron and subsequent nuclear dynamics with significant probability and sub-fs timing precision. Furthermore, we aim at extending attosecond pulse generation at spectroscopically useful flux levels to photon energies of several hundred eV and shortening the pulse duration towards the atomic unit of time (24 as). These advances will permit access to the fastest electron rearrangements, correlations and probe transient populations of ever more deeply bound quantum states. Characterization will be performed routinely with optical-field-driven streak cameras.
We are developing a 20-m-long high-energy attosecond beamline, AS-6, in which our multi-terawatt, few-cycle source, LWS-20 is being gently focused into a series of gas jets for quasi-phase-matched high-order harmonic generation. This infrastructure is aimed at producing microjoule-energy isolated attosecond pulses at photon energies ≥100 eV, resulting in peak powers comparable to those delivered by the XUV free electron laser: FLASH at DESY (Hamburg). This development holds promise for developing attosecond XUV-pump/XUV-probe spectroscopy.

contact: E. Goulielmakislink to the personal page of Eleftherios Goulielmakis, G. Marcus
references:
Intense 1.5-cycle near infrered laser waveforms and their use for the generation of ultra-broadband soft-X-ray harmonic continua, Al. L. Cavalieri et al. New J. Phys. 9, 242 (2007)
Intense few-cycle light pulses in the deep ultraviolet, U. Graf et al. Opt. Express 16, 18956 (2008)
Single-cycle nonlinear optics, E. Goulielmakis et al. Science 320, 1614 (2008)
Coherent superpostion of laser-driven soft-X-ray harmonics from successive sources, J. Serres et al. Nature Physics 3, 878 (2007)
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Fig. 1. State of the art of femtosecond and attosecond technology: millijoule-scale, near-single-cycle laser pulse \lambda_{\rm L}∼750 nm, T_{\rm L}∼3.3 fs and nanojoule-scale, isolated sub-100-as XUV pulse \lambda_{\rm L} ∼15 nm. (© eg)
Fig. 1. State of the art of femtosecond and attosecond technology: millijoule-scale, near-single-cycle laser pulse \lambda_{\rm L}∼750 nm, T_{\rm L}∼3.3 fs and nanojoule-scale, isolated sub-100-as XUV pulse \lambda_{\rm L} ∼15 nm. (© eg)
Fig. 2. Basic concept of high-order harmonic generation from successive sources (a). Increasing the density of atomic dipole emitters tends to increase the coherent harmonic yield. However, increasing density causes the dipole oscillators to rapidly dephase along the laser propagation direction, curve ∗1 in (b). Splitting the generation medium into two or three equal sections and moving them apart so that the phase of the atomic dipole oscillations gets shifted by π in the focused laser beam allows the atomic density to be increased by a factor of 2 and 3, respectively, leading to saturation at a factor of 4 and 9 higher harmonic intensities (curves ∗2 ∗3), respectively. The concept was recently corroborated in a proof-of-principle experiment.
Fig. 2. Basic concept of high-order harmonic generation from successive sources (a). Increasing the density of atomic dipole emitters tends to increase the coherent harmonic yield. However, increasing density causes the dipole oscillators to rapidly dephase along the laser propagation direction, curve ∗1 in (b). Splitting the generation medium into two or three equal sections and moving them apart so that the phase of the atomic dipole oscillations gets shifted by π in the focused laser beam allows the atomic density to be increased by a factor of 2 and 3, respectively, leading to saturation at a factor of 4 and 9 higher harmonic intensities (curves ∗2 ∗3), respectively. The concept was recently corroborated in a proof-of-principle experiment.