A Versatile Setup for Ultrafast Broadband Optical Spectroscopy of Coherent Collective Modes in Strongly Correlated Quantum Systems

Abstract

A femtosecond pump-probe setup is described that is optimised for broadband transient reflectivity experiments on solid samples over a wide range of temperatures. By combining a temporal resolution of 45 fs and a broad detection range between 1.75 and 2.85 eV, this apparatus can provide insightful information on the interplay between coherent collective modes and high-energy electronic excitations, which is one of the distinctive characteristics of strongly interacting and correlated quantum systems. The use of a single-shot readout CMOS array detector at frame rates up to 10 kHz allows to resolve coherent oscillations with amplitudes below 10${}^{-4}$ in $\Delta$R/R. We demonstrate the operation of this setup on the prototypical charge-transfer insulator La${}_2$CuO${}_4$, revealing the presence of coherent optical phonons with frequencies as high as 13 THz.

16 pages, 4 figures