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 temperature range. By combining high temporal resolution and a broad detection window, this apparatus can investigate the interplay between coherent collective modes and high-energy electronic excitations, which is a distinctive characteristic of correlated electron systems. Using a single-shot readout array detector at frame rates of 10 kHz allows resolving coherent oscillations with amplitudes <10-4. We demonstrate its operation on the charge-transfer insulator La2CuO4, revealing coherent phonons with frequencies up to 13 THz and providing access into their Raman matrix elements.