title: Critical field enhancement of asymptotic optical bound states in the continuum.
abstract: We study spectral singularities and critical field enhancement factors associated with embedded photonic bound states in subwavelength periodic Si films. Ultrahigh-Q resonances supporting field enhancement factor exceeding 10(8) are obtained in the spectral vicinity of exact embedded eigenvalues in spite of deep surface modulation and vertical asymmetry of the given structure. Treating relations between the partial resonance Q and field enhancement factors with an analytical coupled-mode model, we derive a general strategy to maximize the field enhancement associated with these photonic bound states in the presence of material dissipation. The analytical expression for the field enhancement quantitatively agrees with rigorous numerical calculations. Therefore, our results provide a general knowledge for designing practical resonance elements based on optical bound states in the continuum in various applications.
authors.affiliation: Department of Electrical Engineering, University of Texas - Arlington, Box 19016, Arlington, TX 76019, USA.
authors.forename: Jae Woong
authors.initials: JW
authors.lastname: Yoon
authors.affiliation: Department of Physics, Hanyang University, Seoul, 133-791, KOREA.
authors.forename: Seok Ho
authors.initials: SH
authors.lastname: Song
authors.affiliation: Department of Electrical Engineering, University of Texas - Arlington, Box 19016, Arlington, TX 76019, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Magnusson