Grating Waveguide Structures
A grating coupler that is extended over the whole surface of the grating results in a combined structure sometimes called a grating waveguide structure. In such a structure, light cannot be guided, as any light coupled in is also coupled out. At resonance, a normally transparent structure becomes reflective. If the grating period is sub-wavelength, then the normally-transparent structure becomes a mirror under resonance conditions. These conditions include the angle, frequency (wavelength), and polarization of the incident light. At resonance, there is also a much higher intensity in the waveguide region. Such intensities are called evanescent as they decay exponentially outside of the waveguide region.
The guided mode resonance can be used to design filters and sensors.
Read more about this topic: Guided-mode Resonance
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