LEDs AND IREDs

Depending on the exact mixture of semiconductors used in manufacture, visible light of any color, as well as infrared (IR), can be produced when current is passed through a diode in the forward direction. The most common color for a light-emitting diode (LED) is bright red, although LEDs are available in many different colors. An infrared-emitting diode (IRED) produces energy at wavelengths slightly longer than those of visible red light. These are called near-infrared (NIR) rays.
The intensity of energy emission from an LED or IRED depends to some extent on the forward current. As the current rises, the brightness increases up to a certain point. If the current continues to rise, no further increase in brilliance takes place. The LED or IRED is then said to be in a state of in saturation.