Optical Waveguide
Fabrications
Jules Billuart & Leo Norilo & Kasperi Kylmänen
Outline
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Deposited Thin Films
◦ Sputtered dielectric films
◦ Deposition from solutions
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Epitaxial Growth
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Motivations and basic principle
Liquid Phase Epitaxy
Molecular Beam Epitaxy
Metal-Organic Chemical Vapor Deposition
Substitutional Dopant Atoms
Deposited Thin Films
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One of the earliest methods
◦ Still, one of the most effective
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Several different methods
◦ Generally inexpensive compared to other alternatives
◦ Was a cornerstone of implementin modern communications
network
Deposited thin films:
Sputtering
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Solid source bombarded with ions
-> Ions remove atoms or molecules
-> Removed particles form a thin film on top of the
substrate
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Good quality film
Deposited thin films:
Sputtering
https://upload.wikimedia.org/wikipedia/en/archive/7/72/200603
29055320!Sputtering.gif
Deposited thin films:
Deposition from solutions
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Solution dries on top of the substrate and forms a
thin film
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Casting or molding techniques may be applied
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Quality of the film not so good
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No sophisticated equipment needed, inexpensive
Epitaxial Growth: basic principle
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Overlap of thin layers
Different component’s concentration
Different refractive indexes
Epitaxial Growth: basic principle
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Refraction index is function of Al concentration
Epitaxial Growth: basic principle
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Refraction index is function of Al concentration
Optical modes function of refractive index (cut-off
conditions)
Liquid Phase Epitaxy
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Precipitation of a solute onto a substrate
Liquid Phase Epitaxy
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Precipitation of a solute onto a substrate
Tipping boat system
Molecular Beam Epitaxy
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Vacuum Chamber
Knudsen effusion cells
RHEED to check the growth process
Thermal emission
Metal-Organic Chemical Vapor
Deposition (MOCVD)
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Growth process achieved by chemical reaction
Flow of gaz within reactor furnace
Very toxic
Deposition Rate
Substitutional dopant atoms
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Fabrication techniques involving dopant atoms
revolve around the same main idea:
Some of the atoms of a substrate material are
replaced with dopant atoms.
→ Waveguides are fabricated straight into, or on top
of a substrate material.
Ion exchange and migration
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Ion exchange and migration techniques use electric
fields in the introduction of dopant atoms.
These techniques include the following steps:
1. Substrate material’s heating in molten dopant material.
2.Switching on the electric field.
3.Migration of the substrate material’s ions towards the
cathode.
4.Migration of the dopant atoms to the now open sites.
Ion exchange and migration
Advantages and disadvantages
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(+) Allows waveguides to be implanted into
amorphous materials.
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(+) Enables the fabrication of buried waveguides.
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(–) The fabrication process can be quite demanding.
Ion implantation
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In ion implantation, dopant atoms are introduced by
impacting them straight into the substrate material.
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This is done using an ion source containing the desired
dopant atoms.
◦ The ions are directed from the source into an accelerator.
◦ After going through the accelerator, the ions are
concentrated between deflector elements into an ion beam.
→ A concentrated collcetion of dopant atoms is introduced to
the substrate material.
Ion implantation
Advantages and disadvantages
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(+) Allows precise implantation of dopant atoms.
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(–) The impacts between dopant atoms and the
substrate material may damage the lattice.
→ Most materials have to be annealed after the
implantation process.
Conclusion
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Deposited thin films
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Epitaxial growth
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Substitutional dopant atoms