Dynamic tuning of lattice plasmon lasers with long coherence characteristics

Here, we experimentally demonstrate dynamic tuning of an optically-pumped lattice plasmon laser based on arrays of gold nanoparticles and liquid gain materials [A. Yang, T. B. Hoang et al., Nature Communications 6, 6939 (2015)]. The structure consists of an array of 120 nm diameter gold disks with a height of 50 nm and 600 nm spacing. A liquid gain material composed of IR-140 dye molecules dissolved in a variety of organic solvents is placed on top of the disks and held in place by a thin glass coverslip. At a lasing wavelength of 860 nm, time-resolved measurements show a dramatic reduction of the decay time from ~1 ns to less than 20 ps when the optical excitation power density increases from below to above the lasing threshold, indicating the transition from spontaneous to stimulated emission. By changing the dielectric environment surrounding the gold disks in real time, the lasing wavelength can be dynamically tuned over a 55 nm range. Finally, we will discuss recent experiments where we probe both the temporal and spatial coherence properties of the lattice plasmon laser. This advance of tunable plasmon lasers offer prospects to enhance and detect weak physical and chemical processes on the nanoscale in real time.