We demonstrate lasing action in a novel microcavity laser device based on vertical cavity surface‐emitting laser technology. This laser can be used for intracavity spectroscopy, high contrast imaging of small (10 &mgr;m) structures, and is well suited for use in micro‐optical mechanical systems for analysis of particles or fluids. Here, we investigate spectra of intracavity polystyrene spheres. Lasing threshold, single‐mode operation, and multimode operation are all studied. Transverse mode separation in the multimode regime is found to be effective for sizing of the spheres.