Extended Data Fig. 5: Optical pump–probe set-up.
From: Coherent control of a surface structural phase transition
a, Ultrashort laser pulses (P1: λc = 1,030 nm, Δτ = 212 fs, ‘Pump’) from an Yb:YAG amplifier (left) pump an OPA (output: P2, λc = 800 nm, Δτ = 232 fs, ‘Probe’). The intensity of the pump beam is modulated at a frequency of 25 kHz by an acousto-optic modulator (AOM). Pump and probe beams are independently attenuated and collinearly focused onto the sample by a single lens (200-mm focal length). The relative on-axis position of the two foci can be adjusted using a telescope assembly. The reflected beams pass two short-pass filters (SP) blocking the pump pulses and are focused on a silicon photodiode (PD). The relative timing between pump and probe pulses is controlled by an optical delay stage. The pump-induced reflectivity changes of the sample are measured by processing the PD and reference signals in a lock-in amplifier. RF, radio-frequency; ND, neutral density.
