Sensitive femtosecond wave-packet spectrometer

Abstract

We developed a highly sensitive femtosecond pump–probe spectrometer suitable for observation of ultrafast phenomena such as wave-packet dynamics and phase relaxation. Unlike the conventional pump–probe spectroscopy, our method does not require lock-in amplifiers. Selective detection of nonlinear signal is possible by combination of a rapid-scanning delay stage and multichannel DC-cut amplifiers, which is the core of our new method. Simultaneous measurement of spectra is also realized with short acquisition time less than 50min. The detection limit is up to 1×10−5. This new method enables us to trace detailed dynamics of vibrational wave packet in condensed matters, and provides information of the potential energy surface and dephasing process.