Bright Optical Eigenmode of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>1</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:msup><mml:mi>nm</mml:mi><mml:mn>3</mml:mn></mml:msup></mml:math>Mode Volume

We report on the discovery and rationale to devise bright single optical eigenmodes that feature quantum-optical mode volumes of about $1\text{ }\text{ }{\mathrm{nm}}^{3}$. Our findings rely development application a quasinormal theory self-consistently treats fields electron nonlocality, spill-out, Landau damping around atomistic protrusions metallic nanoantenna. By outpacing with radiation via properly designed antenna modes, extremely localized modes become efficiencies reaching 30% could provide up $4\ifmmode\times\else\texttimes\fi{}{10}^{7}$ times intensity enhancement.