High-Quality Plasmonic Lasing with Topologically Trivial or Nontrivial Polarization

This paper reports how a simple plasmonic lattice, containing only one metal nanoparticle in the unit cell, can produce lasing beams with various polarization patterns. Using arrays of aluminum nanoparticles covered with dye solutions, we demonstrated topologically trivial and nontrivial lasing in the near-infrared regime under nanosecond-pulsed optical pumping. Although the aluminum nanoparticles exhibit high Ohmic losses, the lasing emissions showed narrow line widths below 0.05 nm and a long coherence time of hundreds of picoseconds. By comparing the polarization-resolved far-field emission patterns with the characteristics of simulated photonic modes, we identified the lasing cavity modes as bound states in the continuum or surface lattice resonances of electric and magnetic types. Our analysis shows that lasing action preferentially emerges from a flatter photonic band, regardless of whether the mode corresponds to a bright surface lattice resonance or a dark bound state in the continuum.