What Is A Semiconductor Laser?

Semiconductor lasers use semiconductor materials as the gain medium. Most semiconductor lasers are electrically pumped laser diodes, where electron-hole pairs are generated by electrical current at the junction between n-type and p-type semiconductor materials. In optically pumped semiconductor lasers, charge carriers are generated through the absorption of pump light.

Laser devices are fabricated on polished semiconductor wafers using photolithography techniques. Common semiconductor gain materials include gallium arsenide (GaAs), aluminum gallium arsenide (AlGaAs), gallium phosphide (GaP), gallium indium phosphide (GaInP), gallium nitride (GaN), indium gallium arsenide (InGaAs), indium phosphide (InP), and gallium indium phosphide (GaInP). These materials are all direct bandgap semiconductors, as indirect bandgap materials such as silicon do not provide efficient light emission.

Although semiconductor lasers exist in various configurations, several important characteristics are common among them:

• High-efficiency electrical pumping can be achieved with moderate voltages, particularly in high-power diode lasers, making them ideal as pump sources for solid-state lasers and other laser systems.

• A wide wavelength range can be obtained through different device structures, covering most of the visible, near-infrared, and mid-infrared spectral regions. Some semiconductor lasers also support wavelength tuning.

• Small laser diodes can achieve extremely fast switching speeds and optical power modulation, making them suitable for applications such as optical data communication transmitters.

From a technological perspective, semiconductor lasers have become the most important category of lasers due to these advantages. Their applications are extremely broad and include optical communications, optical data storage, metrology, spectroscopy, materials processing, laser pumping, and medical technologies.