Abstract

Resonant grating filters offer high-contrast, narrowband reflectivity and transmissivity for an incident plane wave. They differ from other optical filters in that they operate on the principle of resonance excitation, rather than a bragg-type or Fabry-Perot effect. The principle of resonance excitation has been equated with the excitation of a leaky waveguide mode.¹ Connecting the resonance to a leaky mode excitation has led to new design principles for resonance grating filters. For instance, the ideal waveguide dispersion relation has been used to locate the position of the resonance in wavelength or angle.² However, connecting resonant width to leaky waveguide excitation has largely been ignored. We will show how the waveguiding concept can be extended to give approximations to resonant width. This approach is based on three different models: homogeneous RCWA³, an approximate homogeneous modal analysis, and an approximate coupled-mode approach. Note, the term homogenous refers to solving the problem without the existence of an incident plane wave field.

© 1996 Optical Society of America