Laserdiodi

Laserdiodi are semiconductor light sources that emit coherent, monochromatic light via stimulated emission when forward biased. They integrate a p-n junction with an optical cavity and are produced as edge-emitting diodes and vertical-cavity surface-emitting lasers (VCSELs).

Operation relies on population inversion in a semiconductor active region, where injected carriers recombine to emit photons that are amplified by the optical cavity. A threshold current must be exceeded before significant laser action occurs; below threshold, emission is spontaneous and incoherent.

The emitted wavelength is determined by the material bandgap and the cavity design, with common materials including GaAs-based compounds for near-infrared and InP-based systems for telecommunications wavelengths around 1.3–1.55 µm. Single-mode operation is often achieved with distributed feedback (DFB) or distributed Bragg reflector (DBR) structures, while VCSELs typically emit circular beams in the 850–980 nm range, with newer devices extending into the 1–2 µm range.

Fabrication often uses epitaxial growth (MBE or MOVPE) to form quantum wells, followed by ridge or oxide confinement to limit current and optical modes. Fabrication steps include facet coating, as well as optional anti-reflection or high-reflection coatings in external cavities.

Laserdiodi are widely used in fiber-optic communications, data storage, barcode scanning, printing, laser pointers, and sensing systems. They are valued for efficiency, small size, and the potential for direct electrical-to-optical conversion, but they require careful temperature control and current regulation due to wavelength and power dependence on temperature.

Safety concerns include exposure to optical radiation; high-power diodes require protective measures. Advancements continue in power, efficiency, spectral purity, and integration with photonic circuits. The development of laser diodes began in the 1960s with GaAs-based devices, leading to substantial improvements in telecom and consumer applications.