A diode laser is a type of laser that utilizes a diode as the active medium. It operates on the principle of stimulated emission of photons. Here's a brief overview of the construction and working of a diode laser:
Construction:
Semiconductor Material: The diode laser is constructed using a semiconductor material, usually a compound of gallium, arsenic, and indium. Common materials include gallium arsenide (GaAs) and gallium nitride (GaN).
P-N Junction: The diode laser consists of a p-n junction formed by doping the semiconductor material with impurities. The p-side is doped with an acceptor impurity, creating a region with positive charge carriers (holes), while the n-side is doped with a donor impurity, creating a region with negative charge carriers (electrons).
Active Layer: Within the p-n junction is an active layer or quantum well. This layer is typically very thin (a few nanometers) and is designed to have specific energy levels for electrons and holes.
Mirrors: Two mirrors are placed on opposite ends of the diode laser. One mirror is partially reflective, allowing some light to escape, while the other mirror is highly reflective, causing light to bounce back into the active layer. These mirrors form an optical cavity that helps in the amplification of light.
Working:
Forward Bias: When a forward bias voltage is applied across the p-n junction, electrons from the n-side and holes from the p-side begin to move toward the junction.
Recombination: As electrons and holes move towards the junction, they recombine within the active layer. This recombination process results in the release of energy in the form of photons. The energy level of the released photons depends on the bandgap energy of the semiconductor material.
Amplification: The released photons that have the right energy level and direction can undergo stimulated emission, which is when an incoming photon stimulates the emission of another photon with the same energy and direction. This process takes place as the photons travel back and forth between the mirrors, undergoing amplification with each pass.
Output: Some of the amplified photons pass through the partially reflective mirror, forming the laser output. The output beam is coherent and highly focused.
Heat Dissipation: Since diode lasers generate heat during operation, they often incorporate a heatsink or a thermoelectric cooler to dissipate the excess heat and prevent damage to the diode.
Diode lasers are commonly used in various applications, including telecommunications, laser pointers, barcode scanners, laser printers, and medical equipment.
