Abstract
This paper quantifies the lattice expansion of an insulator upon two photon excitation. The ultrafast x-ray diffraction experiments measure a clean quadratic dependence of the strain on the laser fluency and prove that the pulse intensity is the relevant quantity, as the signal is anti-proportional to the pulse duration. The investigated material Bi:YIG is the standard material for magnonics, where ultrashort laser-pulses can create spin-waves via various mechanisms, including strain modulation of the anisotropy
Highlights
By ultrafast x-ray diffraction we quantify the strain from coherent and incoherent phonons generated by one- and two-photon absorption
We investigated the ferrimagnetic insulator bismuth-doped yttrium iron garnet, which is a workhorse for laser-induced spin dynamics that may be excited indirectly via phonons
Ultrafast x-ray diffraction (UXRD) has quantified these strain amplitudes generated in various materials, with a dependence on the incident fluence that is usually linear [5,6,7,8] or sublinear if saturation effects play a role [9]
Summary
Measurement of transient strain induced by two-photon excitation By ultrafast x-ray diffraction we quantify the strain from coherent and incoherent phonons generated by one- and two-photon absorption. We identify the two-photon absorption by the quadratic intensity dependence of the transient strain and confirm a short lifetime of the intermediate state via the inverse proportional dependence on the pump-pulse duration.
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