This a photograph shows a more developed sensor setup to the one described in the Optics Letters paper. In this case, the path length is 10 cm (instead of 40 cm) and the mechanical set-up has been modified. The VCSEL and the optical setup (with a spherical mirror and detector and laser mounted side by side) stayed the same.

The laser that was used in the Optics Letters publication was developed in the framework of a European project in which Siemens, TU Munich and VERTILAS participate among other partners. (Image credit: Andreas Hangauer)