  We present a flexible and efficient ultrafast time-resolved spontaneous Raman
spectroscopy setup to study collective excitation and quasi-particle dynamics
in quantum matter. The setup has a broad energy tuning range extending from the
visible to near infrared spectral regions for both the pump excitation and
Raman probe pulses. Additionally, the balance between energy and
time-resolution can be controlled. A high light collecting efficiency is
realized by high numerical aperture collection optics and a high-throughput
flexible spectrometer. We demonstrate the functionality of the setup with a
study of the zone-center longitudinal optical phonon and hole continuum
dynamics in silicon, and discuss the role of the Raman tensor in time-resolved
Raman scattering. In addition, we show evidence for unequal phonon softening
rates at different high symmetry points in the Brillouin zone of silicon by
means of detecting pump-induced changes in the two-phonon overtone spectrum.
Demagnetization dynamics in the helimagnet Cu2OSeO3 is studied by observing
softening and broadening of a magnon after photo-excitation, underlining the
unique power of measuring transient dynamics in the frequency domain, and the
feasibility to study phase transitions in quantum matter.
