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TR Photon Spectroscopies

Time-Resolved Optical Spectroscopy with broadband probe (TR-OS)
The TR-OS with a broadband supercontinuum light pulse as a probe is a powerful spectroscopy for measuring the time-dependent modification of the dielectric function of the material under scrutiny over ultrafast timescales, after a photoinduced excitation. By simultaneously probing the optical properties over a wide spectral range (visible / near-IR, typically 1 to 3 eV) with a reflectivity or transmittivity experiment, it is possible to learn about the physical origin at the microscopic level that determines the observed transients. At T-ReX, this spectroscopy is implemented in a high sensitivity setup (signal-to-noise ratio >105) thanks to a high repetition-rate laser source (up to 700 kHz) and the high-frequency modulation of the pump-pulse. The pumping options include the fundamental or second harmonics of the Ti:Sapphire laser or the tunable output of an OPA.
This setup is completed with an open-cycle LN / LHe cryostat and allows to measure solid state samples in a wide range of temperatures (4-325 K).
The broadband detection can provide insights in the study of the out-of-equilibrium dynamics of a variety of solid state materials, including topologically ordered compounds and strongly-correlated electron materials.

The figure shows as an example the outcome of a time-resolved reflectivity measurement, performed on a high-temperature cuprate superconductor (Bi2212) in the superconducting phase. The material is excited with a very low fluence level, in order to study the dynamics of quasiparticles in the ground state. The normalized reflectivity variation, DR/R, is reported both as a function of pump-probe delay (t) and the photon energy of the probe beam (w). In this way, both the time and the energy domains can be accessed, in order to learn the timescale of the relaxation dynamics and the transient reflectivity fingerprint at a constant pump-probe delay.

Last Updated on Friday, 11 November 2016 17:22