key points: tg in optical range has been used to study coherent phonons and thermal transport

Key points:• TG in optical range has been used to study

coherent phonons and thermal transport• To move to nano-scale need to reduce

grating period and hence the wavelength• LCLS provides unique opportunity

–> coherence and time resolution• Experimental requirements

–> split and delay of pump and probe

–> generation of overlapping beams• Generalized non-linear X-ray spectroscopy

X-ray four-wave mixing: Transient grating measurements of nano-scale thermo-elastic responses

F. Hofmann, K.A. Nelson

Roseker et al. Optics Letters 34 (12) 2009

X-ray pump-probe splittingTransient grating

Johnson et al. J. Appl. Phys. 110, 113513 (2011)

samplex-ray gratings

signal

Transient grating generation

Heilmann et al. Optics Express 16, 8658 (2008)

Ti film on Si substrate, 0.76μm grating period

Rogers et al. Annu. Rev. Mater. Sci. 30:117–57 (2000)

Decane with alumina nanoparticles

Schmidt et al. J. App. Phys. 103, 083529 2008

Coherent phonons & thermal grating decay