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 compact, efficient, and widely used in various applications, including optical communication, barcode scanners, and laser pointers. These devices produce coherent light, meaning the light waves are in phase and have a specific wavelength. This property makes laser diodes essential in technologies like fiber optics and CD/DVD players. Their small size and low power consumption make them ideal for portable devices.