To study ultrafast electronic coherences in molecular crystals, as well as biological systems, we developed a setup for ultra-broadband two-dimensional Fourier transform spectroscopy. The output of a 6 – 10 kHz Ti:Sa femtosecond laser is broadened by self-phase modulation inside an argon filled hollow core fiber, to produce continuum (500 – 1000 nm) laser pulses that are compressed to sub-10 fs, using a set of chirped mirrors (Ultrafast Innovations). We use the compressed laser pulses to perform photon echo spectroscopy in a passively phase stabilized BOXCARS geometry. Three excitations pulses with time delays τ and T stimulate a third order non-linear signal (the photon echo) that is emitted after a third time delay t (shown in the figure) and heterodyne detected with a local oscillator field (not shown). Fourier transformation along τ and t yields two dimensional correlation spectra of the excitation and detection frequencies at a certain population time T, allowing us to extract information that are “hidden” in classical transient absorption spectroscopy.
A. Al Haddad, A. Chauvet, J. Ojeda, C. Arrell and F. van Mourik et al. Set-up for broadband Fourier-transform multidimensional electronic spectroscopy, in Optics Letters, vol. 40, num. 3, p. 312-315, 2015.