Generation of Intense LWIR Fields via cascaded SRS

Wider research context / theoretical framework

The development of high-peak power, few-cycle, long wave lasers is motivated by the existence of several scaling laws in strong-field interactions, where relevant quantities have a quadratic dependence on the carrier wavelength. This dependence is related to the ponderomotive potential, and it applies, for instance, to the highest photon energy achievable in high harmonic generation, to the critical power in filaments, and to laser-plasma acceleration of electrons. The main limitation in the experimental investigations of these phenomena is the power of the currently available sources at long wavelengths, which are based on multistage OPA amplifiers and which suffers from the typical low efficiency of optical conversion. Other sources emitting directly in the long-wave IR spectral region, like pulsed CO2 lasers, have also been strongly improved, but still lack the peak power which is necessary for strong field experiments.

Hypotheses / research questions / objectives

The objective of this proposal is to develop a conceptually new and way more efficient parametric long wave source, based on a novel, high-power, frequency shifter developed by our group. The higher peak powers available with this method will be used for proof of concept experiments in strong field physics.

Approach / methods

Our group has recently demonstrated a new method, based on stimulated Raman scattering in gas, with an extended interaction a long waveguide. This method allowed us to redshift the spectrum of laser pulses from an Yb amplifier from 1030 to 1280nm with several mJ energy, and to contextually compress such pulses from above 200fs to less than 20fs, with resulting peak powers just below 1Tw. Applying difference frequency generation techniques to the original pulses and their redshift replica in non-linear crystals, it will be possible to generate energetic, few-cycle, CEP stable pulses in the long wave IR spectral region with an overall much higher efficiency as compared to multi-stage OPA. Such pulses shall then be used for proof of principle applications, i.e. wavelength scaling of incoherent hard Xrays and for electron wave-packet holography.

Level of originality / innovation

The proposed method has an overall efficiency of conversion from the available laser sources into the long wave IR much higher than traditional multi-stage OPA systems. On top, it offers further advantages, like simpler experimental setups, the possibility to achieve CEP stable pulses and with much higher peak power.

Primary researchers involved

The applicant P.A. Carpeggiani, and the group leader and co-applicant, A. Baltuska, with the senior members of the scientific staff A. Pugzlys, M. Kitzler. The international co-operators from the Ultrafast Dynamics Group of Kansai Photon Science Institute KPSI, N. Ishii, R. Itakura and T. Endo.