A stable and compact experimental setup for excitation and investigation of large-wave-vector dynamic gratings by ultrashort light pulses is proposed. Its essential parts are an optical transmission diffraction grating and a large-aperture reflecting microscope objective. Varying the demagnification allows one to change the period of the dynamic grating that is created. The working principle and performance are demonstrated by measurement of the dephasing times of TO phonon–polaritons in GaP. The lower limits of the applicable pump pulse duration are analyzed by ray-tracing calculation.
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