A laser diode is a semiconductor device that emits light when an electric current passes through it. It works by using a process called electroluminescence, where electrons recombine with holes in the semiconductor material, releasing energy in the form of light. Laser diodes are commonly used in various applications, including optical communication, barcode scanners, and laser pointers. These devices are compact and efficient, making them ideal for integration into electronic systems. Unlike traditional light sources, laser diodes produce coherent light, which means the light waves are in phase and can travel long distances without spreading out. This property is essential for applications like fiber optics and laser printing.