Theory for bowtie plasmonic nanolasers

We develop a fundamental formulation for electrically-pumped plasmonic semiconductor nanolasers based on a metallic bowtie structure. Because of the negative dielectric constant of the metal at optical frequencies, the effective modal volume of the plasmonic mode can be compressed to the nanometer scale. In addition, the curvature effect of the bowtie tips provides additional field enhancement in the bowtie gap and further reduces the modal volume. With this small modal volume, the required volume of the active region is reduced correspondingly, which significantly decreases the threshold current. The huge field enhancement due to the small modal volume at the gap of the bowtie may overcome the material and radiation losses by increasing both the spontaneous and stimulated emission rates, and it makes the lasing action possible.