For most lasing and photonic applications, it is essential to control the number of lasing modes that are present. In this work, an interface between two topologically distinct photonic crystals is used to ensure single-mode lasing with enhanced light-matter interactions due to a near-diffraction-limited mode volume.

While the sharp emission lines of microlasers are advantageous for cell tagging, their relatively large size can impede cell migration and behavior. Here, Fikouras et al. develop nano-sized lasers that can readily tag and track various types of cells, including through narrow constrictions.