I. Technical Principles and Performance Differences

① Gain Medium
The fiber laser uses a rare-earth-doped glass fiber as the gain medium. Under the action of the pump light, a high power density is formed inside the fiber, leading to the population inversion of the laser energy levels, and laser oscillation is generated through the positive feedback loop of the resonant cavity. The fiber laser has a compact structure and does not require a complex cooling system. Moreover, the flexibility of the fiber gives it more advantages in multi-dimensional space processing applications. The core of a fiber laser is the fiber, which is a flexible, hair-thin glass or plastic filament renowned for its ability to guide light over long distances with minimal loss. This fiber serves as the active gain medium of the laser and is the core of the laser’s operation. However, unlike the undoped glass or plastic fibers used in telecommunications, the fibers in fiber lasers are doped with rare-earth elements, such as erbium or ytterbium. This doping introduces the energy states required for laser operation, enabling the fiber not only to guide light but also to amplify it.
Solid-state lasers (SSL) have solid materials as their unique gain medium at the core. They are typically composed of four main parts: the gain medium, the cooling system, the optical resonant cavity, and the pump source. The gain medium, such as ruby (Cr:Al₂O₃) or neodymium-doped yttrium aluminum garnet (Nd:YAG), is the soul of the solid-state laser. The activated ions (such as Nd³⁺) doped inside it achieve population inversion under the action of the pump light, thus generating laser light. The cooling system is responsible for removing the heat accumulated inside the gain medium due to laser generation, ensuring the stable operation of the laser. The optical resonant cavity forms continuous oscillations through the positive feedback of photons, outputting a laser beam with high monochromaticity and high directivity.
② Performance and Efficiency
Fiber lasers are renowned for their excellent electrical efficiency, thanks to the nature of the fiber cable, which can conduct light with minimal loss. This feature makes fiber lasers incredibly energy-efficient, typically achieving an efficiency of over 30%. The efficiency of solid-state lasers is usually lower, which may be due to the higher losses of their larger gain media and the need for high-intensity lamps for pumping.
③ Beam Quality: Directly Affects the Effectiveness of Lasers in Precision Applications
The single-mode operation of fiber lasers can provide incredibly high beam quality, characterized by tight focusing and minimal divergence. Although solid-state lasers are capable of providing high-quality beams, they usually have difficulty matching the beam quality of fiber lasers, especially at higher power levels. Despite their lower efficiency and beam quality, solid-state lasers are not without their advantages. They have powerful power scaling capabilities and are well-suited for high-power applications. Solid-state lasers can be designed to generate incredibly high power levels by increasing the size of the gain medium and the pumping power, which is not as straightforward for fiber lasers due to the limitations of fiber size and heat dissipation.
④ Stability
Fiber lasers have high stability. Their fiber structure is insensitive to environmental changes (such as temperature, humidity, vibration, etc.) and can maintain a stable working state in relatively harsh environments. At the same time, fiber lasers adopt a solid-state structure and do not contain free-space optical components, so they are considered more durable and adaptable to environmental changes. The stability of solid-state lasers is relatively poor, and changes in environmental factors may have a significant impact on their performance.
⑤ Heat Dissipation Performance
Fiber lasers have excellent heat dissipation performance. Its gain medium is the fiber, which has a large surface area to volume ratio, allowing heat to be dissipated quickly. Therefore, it can work stably for a long time and can withstand high power output. Heat dissipation in solid-state lasers is relatively difficult, and thermal effect problems are likely to occur during high-power operation, affecting the performance and lifespan of the lasers.
⑥ Size and Maintenance Cost
Fiber lasers are very compact and require almost no maintenance. The small size of the fiber and the absence of external mirrors greatly reduce the alignment problems associated with solid-state lasers. In addition, the excellent heat dissipation ability of the fiber usually eliminates the need for active cooling, further reducing maintenance requirements. At the same time, fiber lasers are generally safer to operate because the laser is confined within the fiber, reducing the risk of accidental exposure.
The alignment of the mirrors in solid-state lasers is crucial for their operation and requires regular inspection and adjustment, thus increasing the maintenance workload. In addition, solid-state lasers usually require active cooling to manage the heat generated in the gain medium, which not only increases the complexity of the system but also the maintenance requirements. Solid-state lasers tend to be larger in size than fiber lasers. The need for large mirrors in the gain medium and external mirrors increases their size and weight, limiting their applicability in applications with limited space.