Reusable photonic encryptor enabled by metal-insulator-metal layers
Pietilä, Jesse (2021)
Pietilä, Jesse
2021
Tekniikan ja luonnontieteiden kandidaattiohjelma - Bachelor's Programme in Engineering and Natural Sciences
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2021-05-24
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202105155020
https://urn.fi/URN:NBN:fi:tuni-202105155020
Tiivistelmä
A metal-insulator-metal (MIM) is a scalable optical structure. The cavity formed by planar continuous layers is of great interest as it can give controlled light transmission and reflection at the surface of the MIM structure. On the other hand, the generation of specific colors from the MIM structure is quite difficult, as the optical cavity can absorb a very narrow band and reflects the rest of the light. Nevertheless, in our study, we showed by precisely designing the MIM cavity we can achieve a peak in reflection instead of a dip. The peak in reflection means, the designed cavity is capable of reflecting a narrow band and absorbs the rest of the spectrum.
In this thesis, we use a MIM structure that has been made out of silver and silicon dioxide. We also create a pattern for the silicon dioxide layer. This pattern can be made either visible or invisible, depending on if the upper metal layer is attached or not. Polydimethylsiloxane (PDMS) surface is used to attach and detach the upper metal layer. The patternless structure is studied via computer simulations and the same type of MIM structure with a pattern in silicon dioxide is made in a laboratory. In simulations, we use a software called Lumerical FTDT Solutions what makes it possible to create three-dimensional models of the structure.
The thesis is divided into three parts. In the theoretical section, we study how MIM structures work as optical cavities. Furthermore, we find out how changes in the structure affect the color reflected from the surface. After this, the phenomena are studied with computer simulations. In this part, we study the reflectance of the structure. In simulations, multiple thicknesses are used so that the effect of the different thicknesses can be seen. All the results are presented via graphs and they are later compared to experimental results. In the experimental part of the thesis, we build a MIM structure that resembles the one used in simulations. We also add a pattern to this structure. With the experimental results, we prove that the MIM structure can be used as a reusable optical encryptor.
Based on the simulated results, it can be seen that thickening the silicon dioxide layer causes a redshift. This means that the feature of the cavity shifts to a higher wavelength. This can also be seen as a change in the surface color. Modifying the upper metal layer causes al-so changes, mostly in the amount of light reflected. The experimental result shares the same outcome with simulated results. IR spectroscopy has been used to experimentally record reflectance from the MIM structure that has been fabricated in the cleanroom. We can also come to the conclusion that the MIM structure can be used in optical encryption because the pattern in the silicon dioxide can be made invisible by removing the upper metal layer.
In this thesis, we use a MIM structure that has been made out of silver and silicon dioxide. We also create a pattern for the silicon dioxide layer. This pattern can be made either visible or invisible, depending on if the upper metal layer is attached or not. Polydimethylsiloxane (PDMS) surface is used to attach and detach the upper metal layer. The patternless structure is studied via computer simulations and the same type of MIM structure with a pattern in silicon dioxide is made in a laboratory. In simulations, we use a software called Lumerical FTDT Solutions what makes it possible to create three-dimensional models of the structure.
The thesis is divided into three parts. In the theoretical section, we study how MIM structures work as optical cavities. Furthermore, we find out how changes in the structure affect the color reflected from the surface. After this, the phenomena are studied with computer simulations. In this part, we study the reflectance of the structure. In simulations, multiple thicknesses are used so that the effect of the different thicknesses can be seen. All the results are presented via graphs and they are later compared to experimental results. In the experimental part of the thesis, we build a MIM structure that resembles the one used in simulations. We also add a pattern to this structure. With the experimental results, we prove that the MIM structure can be used as a reusable optical encryptor.
Based on the simulated results, it can be seen that thickening the silicon dioxide layer causes a redshift. This means that the feature of the cavity shifts to a higher wavelength. This can also be seen as a change in the surface color. Modifying the upper metal layer causes al-so changes, mostly in the amount of light reflected. The experimental result shares the same outcome with simulated results. IR spectroscopy has been used to experimentally record reflectance from the MIM structure that has been fabricated in the cleanroom. We can also come to the conclusion that the MIM structure can be used in optical encryption because the pattern in the silicon dioxide can be made invisible by removing the upper metal layer.
Kokoelmat
- Kandidaatintutkielmat [7052]