1. Optical Waveguide Fabrications Jules Billuart & Leo Norilo & Kasperi Kylmänen

2. ● Deposited Thin Films ◦ Sputtered dielectric films ◦ Deposition from solutions ● Epitaxial Growth ◦ Motivations and basic principle ◦ Liquid Phase Epitaxy ◦ Molecular Beam Epitaxy ◦ Metal-Organic Chemical Vapor Deposition ● Substitutional Dopant Atoms Outline

3. ● One of the earliest methods ◦ Still, one of the most effective ● Several different methods ◦ Generally inexpensive compared to other alternatives ◦ Was a cornerstone of implementin modern communications network Deposited Thin Films

4. ● Solid source bombarded with ions -> Ions remove atoms or molecules -> Removed particles form a thin film on top of the substrate ● Good quality film Deposited thin films: Sputtering

5. Deposited thin films: Sputtering https://upload.wikimedia.org/wikipedia/en/archive/7/72/200603 29055320!Sputtering.gif

6. ● Solution dries on top of the substrate and forms a thin film ● Casting or molding techniques may be applied ● Quality of the film not so good ● No sophisticated equipment needed, inexpensive Deposited thin films: Deposition from solutions

7. Epitaxial Growth: basic principle ● Overlap of thin layers ● Different component’s concentration ● Different refractive indexes

8. Epitaxial Growth: basic principle ● Refraction index is function of Al concentration

9. Epitaxial Growth: basic principle ● Refraction index is function of Al concentration ● Optical modes function of refractive index (cut-off conditions)

10. ● Precipitation of a solute onto a substrate Liquid Phase Epitaxy

11. ● Precipitation of a solute onto a substrate ● Tipping boat system Liquid Phase Epitaxy

12. Molecular Beam Epitaxy ● Vacuum Chamber ● Knudsen effusion cells ● RHEED to check the growth process ● Thermal emission

13. ● Growth process achieved by chemical reaction ● Flow of gaz within reactor furnace ● Very toxic ● Deposition Rate Metal-Organic Chemical Vapor Deposition (MOCVD)

14. ● 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. Substitutional dopant atoms

15. ● 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

17. ● (+) Allows waveguides to be implanted into amorphous materials. ● (+) Enables the fabrication of buried waveguides. ● (–) The fabrication process can be quite demanding. Advantages and disadvantages

18. ● In ion implantation, dopant atoms are introduced by impacting them straight into the substrate material. ● 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

20. ● (+) Allows precise implantation of dopant atoms. ● (–) The impacts between dopant atoms and the substrate material may damage the lattice. → Most materials have to be annealed after the implantation process. Advantages and disadvantages

21. ● Deposited thin films ● Epitaxial growth ● Substitutional dopant atoms Conclusion