Figure 2: Light emission below and above the lasing threshold.
From: Lasing in dark and bright modes of a finite-sized plasmonic lattice
Measured emission intensities of a 100 × 100 (μm)2 nanoparticle array (array periods px=py=375 nm, particle diameter d=60 nm) with (a) P=0.7Pth, (b) P=1.3Pth and (c) P=2.0Pth, where Pth is the threshold pump fluence for the higher energy lasing mode. In a–c, the colour bars indicate the emission intensity in arbitrary units. (d) Emission spectra, (e) the mode energies and (f) the mode output powers of the lower (red squares) and higher (blue squares) energy modes as a function of pump fluence. Also shown are the linewidths for lower (higher) energy modes as red (blue) dots. (g) FDTD simulation with the gain medium described as four-level systems, the red (blue) squares corresponding to the lower (higher) energy mode, respectively. We have observed lasing for array periodicities 370–390 nm. Above threshold, we obtain 104 increase in emission intensity, linewidths of 0.2 nm and remarkably low beam divergence of ΔθFWHM=0.3°.
