Graduate student Ganesh Subramania knows just how good a mold the microspheres provide for fabricating photonic crystals. He's the person who makes the crystals, and he does it with surprisingly low-tech and inexpensive equipment. Subramania begins the crystal-construction process by spreading a few drops of a slurry of titania suspension and polystyrene spheres on a glass substrate. Five minutes of compression helps thin the sample and reduces stress cracks in the heat-treatment process that follows. Slow baking is the final step.
Shiny regions are visibly apparent in the remaining photonic crystals.
These regions have characteristic colors that depend on the size of the polystyrene spheres used. If we don't see color, either the scale is wrong or the structure is wrong. It's nice because we can visually inspect some of these to see if they have the right structure. Then Ganesh does scanning electron microscopy on the good samples to see the detailed, periodic structure. And the beat goes on Constant hopes they will eventually be able to make large-area optical photonic crystals using the economical and reproducible ceramic technique.