A merged lattice metal nanohole array based dual-mode plasmonic laser with an ultra-low threshold

Plasmonic lasers offer great potential for cutting-edge, disruptive applications. However, they suffer from a high loss in metals, lack of spatial coherence in the near field, and divergent far-field emission. The challenges are even more significant for a plasmonic laser emitting more than one wavelength mode. The design complexity required for creating multiple modes often limits avenues for minimizing losses and converging far-field emission patterns. This work exploits plasmonic resonances at the junction of a merged lattice metal nanohole array (NHA) and a one-dimensional photonic crystal to achieve dual-mode lasing. The merged lattice NHA is designed by concentrically combining two simple NHAs with different periodicities to create pseudo randomness, leading to enhanced localization and confinement of light in multiple wavelength modes. The proposed structure notably produces intense dual-mode lasing at an ultra-low threshold compared to recent state-of-the-art plasmonic laser demonstrations. The wavelengths of the lasing modes and the separation between them can be tuned over a broad range by changing the structural parameters. The proposed laser also creates a highly directional far-field pattern with a divergence angle of only <0.35 degrees.