102 research outputs found
Picosecond strain dynamics in GeSbTe monitored by time-resolved x-ray diffraction
Coherent phonons (CP) generated by laser pulses on the femtosecond scale have
been proposed as a means to achieve ultrafast, non-thermal switching in
phase-change materials such as GeSbTe(GST). Here we use
ultrafast optical pump pulses to induce coherent acoustic phonons and
stroboscopically measure the corresponding lattice distortions in GST using 100
ps x-ray pulses from the ESRF storage ring. A linear-chain model provides a
good description of the observed changes in the diffraction signal, however,
the magnitudes of the measured shifts are too large to be explained by thermal
effects alone implying the presence of transient non-equilibrium electron
heating in addition to temperature driven expansion. The information on the
movement of atoms during the excitation process can lead to greater insight
into the possibilities of using CP-induced phase-transitions in GST.Comment: 7 pages, 4 figures, Phys. Rev. B, in pres
Entangled-photon Fourier optics
Entangled photons, generated by spontaneous parametric down-conversion from a
second-order nonlinear crystal, present a rich potential for imaging and
image-processing applications. Since this source is an example of a three-wave
mixing process, there is more flexibility in the choices of illumination and
detection wavelengths and in the placement of object(s) to be imaged. Moreover,
this source is entangled, a fact that allows for imaging configurations and
capabilities that cannot be achieved using classical sources of light. In this
paper we examine a number of imaging and image-processing configurations that
can be realized using this source. The formalism that we utilize facilitates
the determination of the dependence of imaging resolution on the physical
parameters of the optical arrangement.Comment: 41 pages, 12 figures, accepted for publication in J. Opt. Soc. Am.
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