A new technique developed by MIT researchers reveals the inner details of photonic crystals, synthetic materials whose exotic optical properties are the subject of widespread research.
Photonic crystals are generally made by drilling millions of closely spaced, minuscule holes in a slab of transparent material, using variations of microchip-fabrication methods. Depending on the exact orientation, size, and spacing of these holes, these materials can exhibit a variety of peculiar optical properties, including "superlensing," which allows for magnification that pushes beyond the normal theoretical limits, and "negative refraction," in which light is bent in a direction opposite to its path through normal transparent materials.
But to understand exactly how light of various colors and from various directions moves through photonic crystals requires extremely complex calculations. Researchers often use highly simplified approaches; for example they may only calculate the behavior of light along a single direction or for a single color.
Instead, the new technique makes the full range of information directly visible. Researchers can use a straightforward laboratory setup to display the information—a pattern of so-called "iso-frequency contours"—in a graphical form that can be simply photographed and examined, in many cases eliminating the need for calculations. The method is described this week in the journal Science Advances, in a paper by MIT postdoc Bo Zhen, recent Wellesley College graduate and MIT affiliate Emma Regan, MIT professors of physics Marin Soljacic and John Joannopoulos, and four others.
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