Highly purified crystals that split light with uncanny precision are key parts of high-powered lenses, specialized optics and, potentially, computers that manipulate light instead of electricity. But producing these crystals by current techniques, such as etching them with a precise beam of electrons, is often extremely difficult and expensive.
Now, researchers at Princeton and Columbia universities have proposed a new method that could allow scientists to customize and grow these specialized materials, known as photonic crystals, with relative ease.
"Our results point to a previously unexplored path for making defect-free crystals using inexpensive ingredients," said Athanassios Panagiotopoulos, the Susan Dod Brown Professor of Chemical and Biological Engineering and one of the paper's authors. "Current methods for making such systems rely on using difficult-to-synthesize particles with narrowly tailored directional interactions."
In an article published online July 21 in the journal Nature Communications, the researchers proposed that photonic crystals could be created from a mixture in which particles of one type are dispersed throughout another material. Called colloidal suspensions, these mixtures include things like milk or fog. Under certain conditions, these dispersed particles can combine into crystals.
Creating solids from colloidal suspensions is not a new idea. In fact, humans have been doing it since the invention of cheese and the butter churn. But there is a big difference between making a wheel of cheddar and a crystal pure enough to split light for an optical circuit.
One of the main challenges for creating these optical crystals is finding a way to create uniform shapes from a given colloidal mixture. By definition, crystals' internal structures are arranged in an ordered pattern. The geometry of
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Princeton University, Engineering School