Experimental data
TIME-RESOLVED DARK-FIELD X-RAY MICROSCOPY
Time-resolved DFXM images how a laser-induced strain field propagates and undergoes mode conversion upon interacting with defects.
The high penetration depth of X-rays enables subsurface wave components to be tracked throughout the bulk.
EXPERIMENTAL DATA
This movie summarizes the full time-resolved DFXM measurement sequence. Periodic intact-state measurements were interleaved with the pump–probe delay scans to verify reversible sample recovery and measurement reproducibility.
Blue arrows indicate the longitudinal strain wave propagating along the depth direction, while red arrows indicate the transverse elastic wave propagating in plane.
A larger beam size enables a broader sample region to be probed. Consistent longitudinal and transverse wave responses are also observed near the dislocation on the right; the red arrows specifically mark the transverse in-plane component.
The same in-plane transverse strain-wave response is observed at a weak-contrast dislocation from 1,000 to 6,000 ps. The red arrow marks its propagation.
SUPPLEMENTARY MATERIAL
Swipe through the analysis—from ultrafast excitation to strain-wave propagation.
In our experimental geometry, the DFXM contrast and its characteristic image shape depend on the dislocation type and orientation. The difference images are obtained by subtracting the perfect-crystal DFXM image from the defect-containing case.
To model strain-wave propagation, a localized strain field was translated laterally and inward; the resulting DFXM contrast shifts agree with geometric predictions and do not represent physical defect motion.
COMSOL two-temperature-model simulation of ultrafast laser excitation in germanium, showing rapid electron heating followed by electron–phonon energy transfer to the lattice.
Stacked DFXM profiles show the overall evolution of the out-of-plane longitudinal and in-plane transverse strain-wave components.