For the investigation of ultrafast processes, it is a widely used method to create a dynamic grating by two intersecting pump pulses and measure the intensity of a probe beam diffracted off this transient grating as a function of its delay. In Ref. 1 the attention was drawn to the fact that the temporal resolution and accuracy of such measurement is limited for ultrashort pump pulses if the intersecting pulses are created by a usual beam splitter and recombined by a standard lens or mirror. This limitation is due to the effect that the pulse fronts of the two intersecting pulses are crossing each other under some angle. Thus the extension of the created interference pattern in the lateral direction is considerably smaller than the beam diameter. Maznev et al. have proposed a setup consisting of an optical transmission grating for beam splitting and a two-lens imaging system, which overcomes this limitation. In this contribution, we suggest an alternative setup to create dynamic gratings by ultrashort light pulses. It utilizes a reflecting microscope objective for imaging of an optical transmission grating onto the sample (see Fig. 1). In this system, the period of the created grating in the sample can be easily changed by changing the demagnification of the objective. We chose a reflective objective in order to eliminate the chromatic aberration.
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