Our pump-probe setup is capable of measuring up to 13 ns of total delay with sub-picosecond time resolution.
Our setup is based around a Coherent MiraHP/Verdi V18 ultrafast laser that emits more than 4 W of mode-locked pulses of duration 200 fs at 80 MHz repetition rate.
Our setup uses two passes of a 1m delay stage to achieve a maximum delay time of 13 ns, corresponding to 4 meters of path length difference.
We have two low temperature cryostats that allow us to perform measurements from 3-500 K.
Our lock-in amplifier is capable of modulating and demodulating at six arbitrary frequencies, allowing us to perform multiple measurements simultaneously.
In our TG implementation, a pump pulse from a microchip laser (532 nm, 1 ns duration) is split using a phase mask, or a custom diffractive optic, into ±1 diffraction orders. These two beams are collimated and focused onto a sample by two achromats, where the laser pulses interfere to form a sinusoidal intensity pattern. The sample absorbs this light and is heated according to the spatial pattern, creating a sinusoidal variation in the dielectric constant and surface displacement. A continous-wave probe beam (514 nm) follows exactly the same path as the pump. On reaching the sample, the probe beam diffracts from the periodic grating on the sample created by the pump excitation. We detect this diffracted light in real time using a fast photodiode and an oscilloscope with 500 MHz bandwidth, yielding the transient temperature decay of the surface. We obtain the thermal diffusivity by extracting the exponential time constant of the thermal decay.
Our group shares a 720 core cluster with several other faculty. The cluster is capable of running serial or large parallel jobs.