Nanoparticle self-assembled technique applied to a whispering-gallery-mode laser

The low threshold microlaser is the fundamental component of integrated optical circuits. The fabrication method of the microcavity determines the dimension and threshold of lasers, while the doping method limits the available gain materials and emitted wavelength. Here we propose a silica nanoparticles self-assembly technique to fabricate a microlaser with a radius of ∼100  um and Q factor of 2000. The aggregation state of gain molecules is investigated to be J-type dimers with high fluorescence to support the laser generation. The laser can emit a ∼600  nm waveband multimode laser with a low threshold of ∼12  μJ. Such a laser is promising as a coherent light source integrated on the photonic microchips and opens up a new orientation in material science.