From symmetric to asymmetric bowtie nanoantennas: electrostatic conformal mapping perspective

Plasmonic nanoantennas have revolutionized the way we study and modulate light-matter interaction. Due to nanofabrication limitations, dimer type nanoantennas always exhibit some degree of asymmetry, which in some cases is desirable. For instance, in sensing applications, asymmetry is sometimes induced by design in plasmonic nanoantennas to favor higher order nonradiative modes with sharp Fano line shapes. Regardless of the actual origin of the asymmetry, unintentional or intentional, an analytical frame that can deal with it seamless would be beneficial for the field. We resort to conformal mapping for this task and we track the influence of the degree of asymmetry of the circular sectors composing gold bowtie nanoantennas on the nonradiative Purcell enhancement of a nearby nanoemitter. This manuscript reviews the contributions of conformal mapping to plasmonic nanoantennas and illustrates the advantages of the elegant analytical solution provided by conformal mapping to grasp physical insight that can serve as a springboard for new plasmonic asymmetric nanoantenna designs.