Combining diffraction of molecules from light gratings with molecular spectroscopy promises unprecedented insights into photophysical and photochemical processes. The most interesting spectral region for this is the UV, as here aromatic amino acids absorb. While pulsed UV gratings are comparatively easy to produce, doing the same for a continuous-wave grating is more challenging. In our latest publication, we show how a standing light wave with several watts of power can be realized in a vacuum environment and explain why this is not an easy task.