What is the difference between a laser diode (LD) and an LED?
Though both laser diodes and LEDs are light outputting devices by injecting current, the light quality is quite different. The light emitted from an LED is a random phase light which is the same as other normal light, but the one emitted from a laser diode is phase matched (also known as coherent light), which allows it to have many unique applications. Such coherent light can be a localized spot size after a collimated parallel and can be sent long distances while maintaining that localization. Also, coherent light has interference characteristics so that it can be applicable to disc reading applications. Moreover, because LDs can have a higher speed operation from LEDs, an LD is suitable for the applications in which a shortly pulsed light is needed. (e.g. a light source for optical pick-up of optical disc drive, light source for optical communication, etc.
Though both laser diodes and LEDs are light outputting devices by injecting current, the light quality is quite different. The light emitted from an LED is a random phase light which is the same as other normal light, but the one emitted from a laser diode is phase matched (also known as coherent light), which allows it to have many unique applications. Such coherent light can be a localized spot size after a collimated parallel and can be sent long distances while maintaining that localization. Also, coherent light has interference characteristics so that it can be applicable to disc reading applications. Moreover, because LDs can have a higher speed operation from LEDs, an LD is suitable for the applications in which a shortly pulsed light is needed. (e.g.
