Japan's National Institute of Information and Communications Technology has completed research that it says could let fiber optic networks use new parts of the spectrum. Using tiny chips of semiconductor material known as quantum dots, NICT scientists have optically transmitted data in an unused frequency band about 10THz wide, about the same width as the bands currently used for optical communication. The researchers speculate they could eventually use a band about 70THz wide, opening up large amounts of spectrum for faster communication.

This experiment was achieved by using a new method of growing quantum dots. Currently, most quantum dots are grown directly on a hospitable surface, a process that sometimes leads to defective "giant dots" (on a quantum scale — so, very large very tiny structures) that can affect performance. To fix this, the team sandwiched an extremely thin film between the different layers of chemicals in which the dots are grown, producing more tightly-packed and even results.

The new quantum dot growing technique separates this study from similar ones undertaken years ago. Quantum dots have long been used to focus lasers, and have been researched as a communication method by companies like Fujitsu. However, a more even quantum dot arrangement could improve the performance of these lasers, especially in optical transmission. The full paper, published in Optics Express in December is available here (PDF).