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Disappearance of modes in planar Bragg waveguides
1Department of Electronic Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong, China.
Optics Letters
|August 19, 2007
Summary
Forbidden bands in Bragg reflectors can shrink, causing guided modes in Bragg waveguides to disappear. Researchers identified conditions for these missing modes, enabling designs that selectively support specific wave polarizations and symmetries.
Area of Science:
- Optics and Photonics
- Waveguide Theory
- Materials Science
Background:
- Bragg reflectors exhibit forbidden bands that restrict light propagation.
- Planar Bragg waveguides guide light using these periodic structures.
- Mode behavior in waveguides is crucial for optical device design.
Purpose of the Study:
- Investigate the shrinking of forbidden bands in Bragg reflectors.
- Analyze the disappearance of guided modes in planar Bragg waveguides.
- Derive conditions for predicting and controlling missing guided modes.
Main Methods:
- Theoretical derivation of conditions for mode disappearance.
- Analysis of forbidden band behavior in Bragg structures.
- Numerical or analytical examples illustrating mode selection.
Main Results:
- Forbidden bands can shrink to points, leading to mode loss.
- Specific classes of guided modes can vanish entirely.
- Design strategies exist to eliminate antisymmetric modes for TE polarization.
- Brewster incidence affects TM polarization mode interpretation.
Conclusions:
- Understanding mode disappearance enables tailored waveguide design.
- Selective mode support (e.g., only symmetric modes) is achievable.
- Bragg waveguide properties can be precisely controlled by manipulating forbidden bands.
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