X-ray optical limits of microdiffraction at arc second angular resolution and application to optoelectronic waveguides

Synchrotron microbeam high-angular resolution diffraction setup is introduced based on a phase zone plate generating a microbeam with the size of 0.35 $\mu $m (vertical) and 0.24 $\mu $m (horizontal) and a perfect Si(004) analyzer crystal providing high angular resolution of about 2 arc sec. The broadening of the ``diffraction'' spot to 2.5 $\mu $m by perfect crystal has been experimentally observed in the diffraction (vertical) plane. This broadening is a consequence of the phase space conservation principle and unavoidable when high angular resolution in microbeam diffraction experiment is required. The use of perfect crystals in a non-dispersive arrangement offers flexibility in trading beam size/flux for resolution by choosing proper crystal or controlling the angular acceptance by changing asymmetry factor. The setup was applied to study strain and thickness variation in selectively grown InGaAlAs-based optoelectronic waveguide arrays with a minimum lateral size of 1.6 $\mu $m.