Dual findings reveal how to control coherence in plasmonic nanolasers

Researchers at the University of Eastern Finland have discovered two key mechanisms that determine coherence in plasmonic lattice lasers, which combine metallic nanoparticle arrays and an optical gain material. In a study published in Laser & Photonics Reviews, the team demonstrated that these nanostructures can generate ultrafast laser pulse modulation by synchronizing multiple lasing modes.

This synchronization occurs through the shared gain medium at plasmonic hotspots, where femtosecond-scale correlations form, effectively linking the lasing modes.

In a second study published in ACS Nano, the researchers found that lasing modes with different topologies and polarizations can coexist without mutual coherence. This was achieved by fabricating gold nanoparticle arrays with varying diameters, which allowed for the simultaneous formation of topologically trivial dipolar modes and topologically nontrivial quasi-bound-state-in-the-continuum (qBIC) modes.

The modes, despite lasing simultaneously, remained mutually incoherent due to their orthogonal polarizations and distinct topological classes. This finding has significant implications for applications requiring multiple optical channels to operate independently, such as sensing and optical communications. By engineering the geometry, lattice structure, mode topology, and polarization of the nanostructures, researchers can control coherence in plasmonic nanolasers, enabling the design of multimode devices for various applications.