A laser diode serves the function of emitting coherent light through stimulated emission of photons. It operates similarly to a regular diode but with additional properties that allow it to produce a narrow, intense beam of light. Laser diodes convert electrical current into light by passing current through a semiconductor material, typically gallium arsenide (GaAs) or indium gallium arsenide (InGaAs), which is housed within a structure that supports optical feedback for stimulated emission. This coherent light emission makes laser diodes useful in various applications where precise and focused light beams are required.
The function of a regular diode, such as a light-emitting diode (LED) or a semiconductor diode, is to allow current to flow in one direction while blocking it in the opposite direction. When forward-biased (positive voltage applied to the anode with respect to the cathode), a diode conducts electricity, emitting light in the case of an LED or allowing current flow in other types of diodes. This property makes diodes essential components in electronics for rectification, signal modulation, switching, and voltage regulation.
Laser diodes find numerous applications across different fields due to their unique ability to emit intense, coherent light. Common applications include optical communication (fiber optics), laser printing, barcode scanners, laser pointers, medical and surgical procedures (lasers for cutting or coagulation), laser sensors for distance measurement (LiDAR), optical storage devices (CDs, DVDs), and scientific research (spectroscopy and microscopy). Their compact size, efficiency, and ability to emit light in specific wavelengths make laser diodes indispensable in modern technology.
The action of a laser diode involves the emission of coherent light through stimulated emission. When current passes through the diode junction, electrons and holes recombine, releasing photons. These photons then stimulate other excited electrons to emit more photons in phase with the initial ones, resulting in a cascade of light emission that is coherent (in phase and directionally aligned). This process generates a highly concentrated and focused beam of light, distinguishing laser diodes from other light sources like LEDs, which emit incoherent light over a broader spectrum.
Using a laser diode involves careful handling and integration into a circuit or system designed to control its operation and focus its emitted light. Laser diodes require appropriate current-limiting circuits to prevent damage from excessive current. They are typically housed in packages that include optics for collimating or focusing the emitted beam. Depending on the application, laser diodes may require additional optics, heat sinks, and control circuitry to ensure reliable operation and to achieve the desired beam characteristics (such as beam divergence and wavelength). Proper safety precautions are essential when using laser diodes to avoid accidental exposure to intense laser light, which can be hazardous to eyes and skin.