We operate a home-built low-temperature (4 K) ultra-high vacuum (UHV) scanning tunneling microscope (STM) with optical access - the so-called Photon STM. We work in these extreme conditions (UHV, 4 K) so that the systems we study are stable on the surface and can be characterized at the atomic limit. Three lenses, located on separate piezoelectric stages for optimized focusing, enable us to collect luminescence and couple light to the tunnel junction of the STM. The luminescence is characterized using single-photon avalanche photodiodes and an optical spectrometer. More details about the technical design can be found in a publication.
Our lab is located in the Precision Laboratory of the Max Planck Institute for Solid State Research. This top-notch infrastructure provides seismic, acoustic, and electromagnetic decoupling from the environment. Our microscope is located in a separate box and stands on >100-ton air-damped concrete block, which provides us with excellent stability to run experiments at individual atoms and molecules. More information about the Precision Lab.