What is a Photonic Crystal?
Photonic crystals, also known as photonic bandgap materials, are periodic nanostructures that can selectively direct wavelengths of light in much the same way as semiconductors on a computer chip selectively let through certain electronic energy bands. The term “bandgap” merely refers to gaps in the spectral band of light shining through. A rainbow, for instance, lacks band gaps, because water is transparent and does not absorb any specific frequency. A rainbow going through a photonic crystal would have selective gaps depending on the particular nanostructure within the crystal. There are a couple of natural materials which approximate the structure of a photonic crystal. One of them is the gemstone opal. Its rainbow-like iridescence is caused by periodic nanostructures within. The periodicity of the nanostructure determines which wavelengths of light are permitted through and which aren’t. The period of the structure must be half the wavelength of the light that is allowed through. T
Ages: Designed for grades 4-6 Time: about 1 1/2 – 2 classes a. model building will take approximately 30-45 minutes b. model must dry for at least 30 minutes Objectives: Upon completion of this lesson, students will be able to: a. explain the definition of a photonic crystal b. explain the basic structure of a photonic crystal c. construct a model of a photonic crystal d. gather information from a website Primary Subjects: Science Materials: a. computers with internet access – at least one for every 2-3 students b. popsicle sticks – 24 per student or group of students building a model c. glue – 1 glue bottle per 2 models being built; not much glue will be used, but the dispensing mechanism of the glue bottle is necessary frequently in the construction of the model d. printout of directions for building a model of a photonic crystal (unless directions are accessed directly through the internet by students) – 1 per model being built; file can be found at bottom of page e. printout of wor
Let’s start at the beginning: photonic /fO-‘t-nik/ adjective: concerning a quantum of electromagnetic energy In normal language, this means that a photon is an amount of energy that shows itself as light. Something that is photonic deals with that energy. crystal /’kris-t&l/ noun: a homogenous solid formed by a repeating, three-dimensional pattern of atoms, ions, or molecules and having fixed distances between constituent parts What!?!? What they really mean is that a crystal is something that is made of pieces that form a repeating pattern. So, a photonic crystal would be something that deals with light energy, and is made up of small pieces in a repeating pattern. Here is a picture of a photonic crystal. Can you see the repeating pattern? Here, I’ll explain exactly what it is. In photonic crystals, the pattern can be seen in layers. Each layer is made up of many bars laid next to each other, like this: That is what the first layer would look like, just a row of bars. The second layer
