The electric field characterization in the temporal (spectral) domain is of paramount importance for most of our R&D activity and is in itself a R&D program. Among the different techniques, we chose to focus our efforts on the SPIDER (self referencing interferometric technique). Our first SPIDER apparatus, operational since 1999 (following collaboration with the LOA), measures pulses in the range of 20 to some hundreds of fs with a good accuracy and was used in closed loop experiments.
During the last years, our main goals have been to extend the wavelength and temporal ranges of measurement. In particular, we need to measure pulses at the second and third harmonic of the fundamental wavelength of the TiS in order to characterize the harmonics generated in our “achromatic generator” and to optimize their compression. Future R&D on NOPAs (Non collinear Optical Pulse Amplifiers) will call for a characterization of pulses in the visible range as well. Filamentation experiments aimed at obtaining energetic 10 fs pulses also require accurate determination of the electric field in order to optimize the compression scheme.
We designed our second SPIDER system, of which a layout is given in figure 5, to reach these goals. It will enable measuring pulse durations down to less than 10 fs and up to hundreds of fs, at 800 nm but also at 400 nm or 266 nm. Extensive validation tests, software improvements and simulations aimed at fully understand the system limitations are still in progress. An evolution compatible with visible pulses will be available shortly.