The team looked at photoluminescence — the emission of light when electrons are stimulated — in gold nanorods.

It turns out that emissions depend on the shape of the gold nanorods, which are about 20 nm wide and range from 70 to 300 nm long. The rodlike shape is important because it sets the energy of the collective electronic excitations that radiate light. It also boosts absorption, especially in the near infrared, to levels enough to cause luminescence in the nanorods when an ultrafast titanium-sapphire laser beam at 800 nm hits them. The insights may bring advanced optical chips for computers or for switches and routers in fiber networks.