Opto-electronics is the study and application of electronic devices and systems that source, detect and control light, usually considered a sub-field of pho-tonics. In this context, light often includes invisible forms of radiation such as gamma rays, X-rays, ultraviolet and infrared, in addition to visible light.Blue, green, and red LEDs. These can be combined to produce all colors and white. Infrared and ultraviolet (UVA) LEDs are also available.
For Infra-red & red light Aluminium gallium arsenide(AlGaAs).
For green colour light use Aluminium gallium phosphide (AlGaP).
For yellow, orange, red colour light use Gallium arsenide phosphide(GaAsP).