Laser diodes are semiconductor-based lasers that produce coherent light at a single wavelength. A laser diode generally consists of a p-n junction formed between two pieces of semiconductor material, such as gallium arsenide, along with reflector and output coupler components. Laser diodes are self-contained sources of light that work by allowing electrical current to flow through the diode, which causes electrons to be released from the p-n junction. The electrons then recombine with other atoms and molecules in the diode and release energy in the form of light. The laser diode is collimated, meaning the laser beam is highly focused and directional. Due to their small size and high efficiency, laser diodes are used in a wide variety of applications, including optical storage, barcode scanners, laser printers, medical applications, consumer electronics, and more.