Abstract

Photonic Crystals

Florian Kotzur, Stefan Krumpen

A photonic crystal is a periodic dielectric structure which affects the propagation of electromagnetic waves such as light. Opals are a natural example, their iridescent colors do not originate from pigments, but they result from a regular arrangement of cristobalite spheres. Only a few years ago, researchers succeeded in fabricating artificial photonic crystals for light, opening up a branch of solid state physics that promises numerous novel products, such as efficient light sources, miniaturized waveguides, perfect dielectric mirrors as well as novel functional structures for nanophotonics and optical data processing that uses photons rather than electrons. Even though the experts are still working on many problems, we want to enter this research area with the simple means available at our school. We started with acoustic experiments by building an acoustic crystal designed to have a bandgap around 8 kHz (Figs. 1 and 2).

Experimental setup with acoustic crystal

Fig. 1: Experimental setup with acoustic crystal

Acoustic bandgap around 8 kHz

Fig. 2: Acoustic bandgap around 8 kHz

After successfully demonstrating an acoustic bandgap, we built a crystal for microwaves. By adding defects to our microwave crystal we were able to guide the microwaves around extremely sharp bends and to decouple them in a way that resembles current research on photonic crystals by experts (Figs. 3 and 4).

Photonic crystal with a defect

Fig. 3: Photonic crystal with a defect (not our work)

Our microwave crystal with a defect

Fig. 4: Our microwave crystal with a defect

These successful experiments encouraged us to tackle the more difficult fabrication of photonic crystals for light. After numerous attempts we did successfully fabricate a photonic crystal with a photonic bandgap at school (Figs. 5-7).

Scanning electron micrograph of nanoscale SiO2 spheres that we manufactured ourselves

Fig. 5: Scanning electron micrograph of nanoscale SiO2 spheres that we manufactured ourselves

The first photonic crystal that we fabricated at school

Fig. 6: The first photonic crystal that we fabricated at school

Detection of the photonic bandgap

Fig. 7: Detection of the photonic bandgap

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