Spotlight on Optics

Spotlight summary: Light sources have an indispensable role in everyday life. From the first lamp using animal fat around 70,000 BC, to modern light sources, these have been widely used and developed for diverse applications going much beyond night lighting. For example, light-emitting diodes (LEDs) have been extensively utilized in illumination, e.g. as backlight for various mobile units (such as laptop displays and mobile phones). A key component of modern light sources (LEDs and lasers) is the gain material, emitting photons when electrically or optically pumped. Thus far, this has been mainly based on traditional semiconductors: blue LEDs rely on GaN and InGaN, laser diodes for fiber-optic communications are typically based on InGaAsP.