Lasers are the core component of the laser industry, and they come in various types. Common classification methods include the laser’s active medium, chemical composition, operating mode, wavelength range, and excitation method. Different types of lasers have their own advantages and disadvantages, and the selection needs to be based on actual application requirements. This article focuses on introducing two common types of lasers: semiconductor lasers and fiber lasers, and comparing their differences.
I. Key Differences Between Semiconductor Lasers and Fiber Lasers
1.Medium Material:
This is the most fundamental difference between the two. The gain medium of a fiber laser is optical fiber, while a semiconductor laser uses semiconductor materials, such as gallium arsenide (GaAs) and indium gallium arsenide (InGaAs).
2.Light Emission Mechanism:
Semiconductor lasers generate photons through the transition of electrons between the conduction band and the valence band, using electrical excitation to achieve direct electro-optical conversion. Fiber lasers, on the other hand, cannot directly perform electro-optical conversion. They require light (usually from a laser diode) to pump the gain medium, achieving optical-optical conversion.
3.Heat Dissipation Performance:
Fiber lasers have better heat dissipation performance and can usually be cooled by air. Semiconductor lasers are more sensitive to temperature and require a water cooling system to control the temperature when the power is high.
4.Main Characteristics:
- Fiber Lasers: Compact, flexible, with a rich output laser spectrum, good monochromaticity, wide tuning range, performance independent of light polarization direction, low coupling loss between devices and optical fibers, high conversion efficiency, and low laser threshold. The geometry of the optical fiber makes its volume and surface area very small, and in single-mode operation, the laser and pump light can be fully coupled.
- Semiconductor Lasers: Easy to integrate with other semiconductor devices, can be directly electrically modulated, easy to achieve optoelectronic integration, small size, light weight, low driving power and current, high efficiency, long service life, compatible with semiconductor manufacturing technology, and suitable for mass production.
5.Application Fields:
- Fiber Lasers: Widely used in laser fiber communication, laser space long-distance communication, industrial shipbuilding, automobile manufacturing, laser engraving, laser marking, laser cutting, printing roller making, metal and non-metal drilling, cutting, and welding (including brazing, quenching, cladding, and deep welding), military national defense security, medical equipment and instruments, large-scale infrastructure construction, and as a pump source for other lasers.
- Semiconductor Lasers: Widely used in laser ranging, LiDAR, laser communication, laser simulation weapons, laser warning, laser guidance and tracking, ignition and detonation, automatic control, and testing instruments.
II. Basic Composition of a Fiber Laser
Similar to traditional solid-state and gas lasers, a fiber laser also consists of three basic elements: a pump source, a gain medium, and a resonant cavity. The pump source usually uses a high-power semiconductor laser, the gain medium is rare-earth-doped fiber or ordinary nonlinear fiber, and the resonant cavity can be composed of optical feedback elements such as fiber Bragg gratings to form various linear or ring resonant cavities. The pump light is coupled into the gain fiber through an optical system. After absorbing the pump light, the gain fiber forms population inversion or nonlinear gain and generates spontaneous emission. The spontaneously emitted light is subjected to stimulated amplification and mode selection by the resonant cavity, and finally forms a stable laser output.