We report a critical narrowing and sharpening of resonances of a potential well when their eigenfrequencies approach the edge of the continuum. The resonances also obtain sharply peaked shapes with the discontinuity of their slopes. The situation can be realized for an electromagnetic wave propagating across dielectric thin films with a periodically modulated interface(s). We show the phenomenon semianalytically on a general model of a driven quantum potential well, and also by rigorous numerical analysis of Maxwell equations for the wave propagation across the thin film with a modulated interface(s). We justify the phenomenon experimentally, by measurements of light reflection from a dielectric thin film deposited on a periodically modulated surface. The narrow and sharply peaked resonances can be used for an efficient narrow-band frequency and spatial filtering of light.

Close

PrevNext

View figure in article

• Interference & diffraction of light
• Nonrelativistic wave equations
• Schroedinger equation
• Dielectrics
• Thin films
• Classical electromagnetism
• Differential equations