Femtosecond Laser Spectroscopy Lab
Broadband fs transient absorption and transient fluorescence measurements are accomplished with commercial setups (Helios FIRE and Halcyone, respectively) from Ultrafast Systems. Stationary UV-Vis (UV-2600, Shimadzu) and time-correlated single-photon counting (LifeSpec II, Edinburgh Instruments) spectrometers complete this facility with very broad spectral (UV-Vis-NIR) and temporal (fs-ms) coverage. Processes can be monitored with broadband techniques via transient absorption or fluorescence with a time resolution of 100 fs and with time scales ranging from few ps to sub-ms. The laser source can also be used for other (flexible) experiments, for which an additional 3 m2 optical table is available.
Femtosecond Laser Source: The primary laser source is a femtosecond Ti:Sapphire ampli-fied laser system (Astrella, Coherent). It delivers 1.6 mJ, 90 fs pulses centred at 800 nm and with a repetition rate of 4 kHz. The laser beam is split and telescoped for continuum generation in the transient absorption setup, for optical gating in the fluorescence up-conversion spectrograph and for pumping (0.65 mJ) two collinear optical parametric amplifiers (TOPAS Prime, Light Conversion). The latter are used for optical pumping in the transient absorption and fluorescence setups. The excitation wavelengths are continuously tunable from the UV to the near IR.
Femtosecond Transient Absorption Setup: The Helios FIRE transient absorption spectro-graph is equipped with selectable spectral windows covering the range between 330 and 1600 nm. A high-speed linear delay line scans pump-probe delays up to 8 ns.
Fluorescence Up-Conversion Setup: The HALCYONE up-conversion spectrograph is a broadband (450-770 nm) system equipped with a CCD (Andor iDus) and a high-speed delay line. The latter scans pump-gate delays up to 8 ns. Fluorescence is gated with the fundamental Ti:Sapphire beam at 800 nm.
Anindependent time-correlated single-photon counting spectrometer (Life Spec II, Edinburgh Instruments) extends the available delay range of the time-resolved fluorescence techniques to the microsecond timescale. The Life Spec II allows us to measure lifetimes down to 5 ps after deconvolution. Several acquisition modes are available: steady-state fluorescence, fluorescence decay, time-resolved emission spectra and automated time-resolved anisotropy. Available excitation wavelengths are 475, 575 and 635 nm at MHz repetition rates and with pulse durations in the range of 100