Photosensitivity and Refractive-index Modification of Glass: Optical Fiber Applications

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Photosensitivity and Refractive-index
Modification of Glass Optical Fiber Applications

• Narin Nuttavut
• Physics Department, Faculty of Science
• Mahidol University

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Outline

• Photosensitivity
• Application for Bragg gratings
• Refractive-index modification
• Applications
• Future work and direction

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Photosensitivity

• Refractive index changed by light exposure (UV
  band)
• Photo-induced refractivity due to impurities

UV light
Refractive index
noDn (0. 1)
no
Glass
Intensity time
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Bragg gratings

• Bragg gratings

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Bragg gratings

• Fabrication

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Common characteristics

• A large number of layers resulting in a strong
  and narrow bandwidth which can satisfy rigorous
  dense-wavelength telecommunication requirements.
• Sensitivity to environmental parameters, e.g.
  strain and temperature.
• A compact and passive device

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Refractive-index modification something deeper

• Refractive index modification can be achieved by
  several techniques such as heat treatment, strain
  treatment, and chemical processes (or even a
  combination of these).

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An example

• Mirage effect Atmospheric optical illusion in
  which an observer sees a nonexistent body of
  water or an image of some object, resulting from
  distortion of light by alternate layers of hot
  and cool air

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Applications

• Lenses without curve surfaces
• Optical component fabrication

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Optical lenses

• What is a lens?

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GRIN lens

• Rather than varying thickness of the medium, the
  refractive index is changed as a function of the
  diameter of the lens.
• GRIN lens GRaded INdex lens

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A Melles Griots drawing
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Collimator (GRIN lens design)

• Collimators

A Melles Griots drawing
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Future work and direction

• Investigation of refractive-index modification
  for commercial interest
• Investigation of refractive-index modification of
  glass and polymer
• Enhancement processes for refractive-index
  modification

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Recommended references

• K O Hill, et al. Applied Physics Letters,
  32647649, 1978.
• K O Hill, et al. Journal of Lightwave Technology,
  15(8)1263-76, 1997.
• D K W Lam, et al. Applied Optics, 20(3)440-5,
  1981.
• Y J Rao. Measurement Science and Technology,
  8(4)355-375, 1997.

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Acknowledgements

• The author would like to thank
• Staffs of Physics Department, Mahidol University
  for internal discussion and their encouragement.
• The parents/friends for their great understanding
  of having a son/friend who is a researcher.

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Appendix

• Early setup of Bragg gratings recorded in fiber
  (Hill, 1978).