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Cladding mode coupling in highly localized fiber Bragg gratings II: complete vectorial analysis.
Jens U Thomas1, Nemanja Jovanovic, Ria G Krämer
1Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universit¨at Jena, Max-Wien-Platz 1, 07743 Jena, Germany. thomas@iap.uni-jena.de
Optics Express
|October 6, 2012
Summary
Localized fiber gratings strongly couple to high-order cladding modes. This study analyzes these reflected modes, revealing their polarization and intensity distributions are tied to dispersive properties and coupling strengths.
Area of Science:
- Optics and Photonics
- Fiber Optic Sensing
Background:
- Fiber Bragg gratings (FBGs) are crucial optical components.
- Ultrashort pulse inscription enables precise FBG fabrication.
- Coupling to cladding modes is a key phenomenon in FBGs.
Purpose of the Study:
- To analyze the vectorial nature of reflected cladding modes from localized fiber Bragg gratings.
- To investigate the relationship between mode properties and grating characteristics.
- To understand the abrupt transitions in mode behavior.
Main Methods:
- Point-by-point inscription of highly localized FBGs using focused ultrashort pulses.
- Detailed analysis of reflected cladding modes, considering their polarization, orientation, and degeneracies.
- Correlation of observed mode distributions with dispersive properties and coupling strengths.
Main Results:
- Strong coupling to high azimuthal and radial order cladding modes was observed.
- Vectorial analysis revealed direct links between mode polarization/intensity and dispersive properties.
- Abrupt transitions in mode nature were found to be strongly correlated with coupling strength variations.
Conclusions:
- The vectorial nature and degeneracies of reflected cladding modes are critical for understanding localized FBGs.
- Dispersive properties and coupling strengths significantly influence mode behavior and transitions.
- This analysis provides a deeper insight into light propagation in complex fiber gratings.
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