title: Broadband pump-probe spectroscopy at 20-MHz modulation frequency.
abstract: We introduce an innovative high-sensitivity broadband pump-probe spectroscopy system, based on Fourier-transform detection, operating at 20-MHz modulation frequency. A common-mode interferometer employing birefringent wedges creates two phase-locked delayed replicas of the broadband probe pulse, interfering at a single photodetector. A single-channel lock-in amplifier demodulates the interferogram, whose Fourier transform provides the differential transmission spectrum. Our approach combines broad spectral coverage with high sensitivity, due to high-frequency modulation and detection. We demonstrate its performances by measuring two-dimensional differential transmission maps of a carbon nanotubes sample, simultaneously acquiring the signal over the entire 950-1350 nm range with 2.7·10-6rms noise over 1.5 s integration time.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Preda
authors.forename: Vikas
authors.initials: V
authors.lastname: Kumar
authors.forename: Francesco
authors.initials: F
authors.lastname: Crisafi
authors.forename: Diana Gisell
authors.initials: DG
authors.lastname: Figueroa Del Valle
authors.forename: Giulio
authors.initials: G
authors.lastname: Cerullo
authors.forename: Dario
authors.initials: D
authors.lastname: Polli