Fiber laser - functionality and areas of application

• Definition: Solid-state lasers guiding light within optical glass fibers, typically doped with rare-earth elements. 

• Key strengths: Exceptional precision, high efficiency, versatility, and robustness. 

• Applications: Intricate engraving/marking 

• Advantages: Compact design, energy efficiency, long lifespan, low maintenance, non-contact process 

• Limitations: Not ideal for organic materials like wood or transparent materials (clear glass),  or some plastics 

In manufacturing and design, laser technology as a whole has revolutionized material processing. Out of all lasers, fiber lasers stand out due to their precision, efficiency, and marking flexibility in applications. This guide explains fiber lasers, their advantages, common applications, and important safety considerations that are relevant when choosing a new laser. 

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A fiber laser is a solid-state laser, where both the laser light and the pump light are guided within optical glass fibers. The laser's active medium is the glass fiber's internal cross-sectional area, often doped with a rare-earth element like ytterbium. 

In more detail, laser diodes supply energy, delivering light (e.g., at 915nm, 977nm or 1064 nm) to the doped glass fiber via optical fibers. These optical fibers connect through splicing, a glass welding process that eliminates open beam paths for pump or laser light. This makes fiber lasers exceptionally robust against contamination and vibrations. 

Most fiber lasers for marking and engraving are pulsed fiber lasers, often using a MOPA (Master Oscillator Power Amplifier) design. This single-pass amplification in a coiled fiber enables a large amplifier range and high gain within a compact volume. 

Pulsed fiber lasers typically have a pulse peak power of 10kW-20kW and an average output power of 10W-100W, making them suitable for diverse precision tasks. Their high beam quality and excellent focus enable several applications: 

• Complex engraving and marking: Fiber lasers excel at delivering permanent, high-contrast markings on metals, certain plastics, and ceramics. Engraving and marking detailed patterns in high resolution is easily possible, which makes them perfect for engraving designs, text, logos, or serial numbers. Additionally deep engraving is no problem for fiber lasers due to their special power density. Therefore, the applications of the fiber lasers produced by Trotec range from the jewelry to the automotive industry.    
• Additional applications of fiber lasers in general: Additionally, some fiber lasers can also be used for welding or surface cleaning and are also finding more and more applications in other areas. 

When choosing a laser system, you will encounter various technologies, where choosing the right one for your use case can be overwhelming. The following comparison can give you an overview of the differences between the types of lasers. 

Fiber Laser vs. CO2 Laser: 

• Speed & materials: With a wavelength of 1.064 micrometers, fiber lasers produce an extremely small focal diameter.As a result their intensity is up to 100 times higher than that of CO2 lasers with the same emitted average power. Therefore, fiber lasers are optimally suited for metal marking by way of annealing, for metal engraving, and for high-contrast plastic markings.  

•  On the other hand, CO2 lasers, with their longer wavelength, are ideal for cutting, engraving, and marking non-metallic materials like wood, acrylic, leather, paper, textiles, and glass. 

• Precision & beam quality: In comparison, fiber lasers typically offer higher precision and finer beam quality, resulting in smoother cut edges on metals. 

• Maintenance & lifespan: Fiber lasers generally have a longer lifespan and require little maintenance because of contactless marking and engraving and no war parts.

Fiber Laser vs. Nd:YAG Laser: 

• Use cases: Pulsed fiber lasers have partially replaced traditional YAG lasers for many applications, especially marking and engraving. Fiber lasers are generally better suited for industrial metalworking and high-speed production. 

• Pulse: YAG lasers can have higher pulse peak powers (30-100kW), compared to 10kW-20kW of fiber lasers. 

• Usability: Fiber lasers offer significant advantages in design compactness, robustness, longevity, and overall cost-effectiveness. 

Fiber Laser vs. Diode Laser  

• Material and application versatility: Fiber lasers typically operate at 1064 nm. This wavelength is highly absorbed by metals, making fiber lasers ideal for marking metals and certain plastics. Diode lasers commonly operate at 450 nm (blue light) or sometimes around 808–980 nm (infrared) depending on the diode type. Blue diodes (450 nm) are well absorbed by organic materials like wood, leather, and some plastics, in addition to marking some metals. So, fiber laser are mainly used for special purposes in metal and plastic marking, whereas diode laser offer broader versatility across different materials. 

• Deep engraving on metals: Fiber lasers are suitable for deep engraving on metals, while diode lasers cannot achieve the same depth in metal marking. 

• Budget: Diode laser systems (like the Speedy 100 cross ) often provide a larger marking area at a lower cost compared to many galvo fiber laser systems.  

The energy is supplied by laser diodes, whose light (often 915nm or 977nm) is brought to the doped glass fiber via optical fibers. The optical fibers are interconnected via splicing (welding of glass), i.e. often there are no open beam routes for pump or laser light (see Figure 1). As a result, the fiber laser is relatively insensitive to contamination and vibrations. As the pump diodes are spatially separated from one another and each has its own heat sink, the service life of the pump diodes is high. As long as the peak power of the laser pulses is kept below about 10 – 20kW, this results in a high overall service life of several tens of thousands of hours. There are continuously emitting fiber lasers (“cw” = continuous wave) as well as pulsed fiber lasers. Only pulsed fiber lasers will be discussed below, as they are much better suited for marking and engraving applications. The pulse durations are typically around 100 nanoseconds - shorter pulses of a few nanoseconds are achievable, but only at significantly lower pulse energy.

The pulsed fiber lasers in the “MOPA” design consist of a “master oscillator” (also “seed laser”) and a fiber-coupled “power amplifier”. The former is either a diode laser or a “laser on a chip” with an average power of a few milliwatts to a maximum of about 150mW. The laser emits pulses with a defined pulse shape. The “laser on a chip” houses a laser on a single chip - laser-active medium, reflectors and other optical components are often not only integrated but constructed monolithically. The amplifier consists of a ytterbium-doped glass fiber, which is supplied with energy via fiber-coupled pump diodes. If a laser pulse is to be generated, the pump diodes first charge (population inversion) the amplifier fiber. Before it discharges by spontaneous emission, the seed laser emits a pulse that is amplified a few hundredfold to a thousandfold as it passes through the fiber. The amplification takes place in a single pass (“single-pass amplifier”). The fiber is often in coil form - therefore in a small volume, a large amplifier range and thus high gain can be realized.

One significant advantage of fiber lasers is their impressive longevity. Spatially separated pump diodes, each with its own heat sink, contribute to a high service life for these critical components. Fiber lasers generally boast an overall service life of 50,000 to 100,000 hours of operation before major maintenance or significant deterioration. This extended lifespan makes them a smart long-term investment. 

Fiber lasers offer several compelling benefits: 

• Fast & high quality markings particularly on metals and plastics 
• High precision also on fine and detailed markings 
• Compact and maintenance-free design: The large surface area and low volume of glass fibers enable effective cooling, contributing to a compact, robust, and virtually maintenance-free design. 
• Energy efficiency: They boast high electrical-optical efficiency (over 20%), leading to lower energy costs and reduced waste heat during operation. 
• Lower overall costs: Compared to older YAG lasers, fiber lasers have significantly lower overall service life costs for similar applications, making them a more economical choice in the long run. 
• Resilience to contamination: Internal guidance of pump and laser light within optical fibers, achieved through precision splicing, eliminates open beam paths, making them highly resilient to dust and other contaminants. 

Despite their immense capabilities, fiber lasers have limitations regarding material compatibility: 

• Transparent materials: Materials like clear glass are challenging for fiber lasers. The wavelength of fiber lasers is not readily absorbed by transparent materials, leading to poor or no engraving/cutting results.  
• Wood: Fiber lasers are not ideal for cutting or deep engraving wood. Wood's organic, uneven structure often leads to no or inconsistent results. Here CO2 lasers are generally the preferred choice for cutting or engraving. 
• Certain plastics: In general, good marking results on plastics can be achieved with a fiber laser. Here the pigments in the plastic create a lighter or darker coloration depending on the pigmentation, where dark pigments cause lighter coloration and lighter plastics achieve a darker coloration. On the other hand, some plastics cannot be marked due to their heat-sensitivity, which depends a lot on the compositions of the plastic.   
• Materials with risk of fiber damage: Generating pulses with very short duration and high energy can create extremely high peak intensities within the small cross-section of the glass fiber, potentially damaging the fiber by forming "color centers”. 
• Other unsuitable materials: Materials containing chromium (VI) like some leathers, carbon fibers, PVC, PVB, PTFE (Teflon), and beryllium oxide should never be processed with any laser due to the release of toxic fumes.

Fiber lasers emit intense radiation that can be harmful. Therefore, safety is paramount when operating any laser system. The key safety points include: 

• Eye & skin protection: Direct exposure to the laser beam can cause severe and permanent eye damage or cause skin burns. Even so, no additional protection requirements like appropriate laser safety glasses are needed with Trotec lasers, since only lasers of laser class 2 are provided.  
• Fumes and particulates: Fiber laser cutting generates fumes, dust, and particulates. Hence, proper ventilation and extraction systems are essential to prevent inhalation risks and maintain a safe working environment. 
• Fire hazards: The intense heat can ignite flammable materials. Therefore ensuring your workspace is clear of combustibles is required. 

Adhering to these precautions as well as strict safety protocols is crucial to protect both operators and those nearby. 

Considering their high efficiency, long lifespan, and exceptional precision on metals and plastics, fiber lasers are often a well-suited investment. The benefits in terms of speed, quality, and versatility often justify investing in a high-quality fiber laser, especially for businesses focused on metal processing and high-precision applications. 

If your primary needs involve engraving or marking metals with unparalleled precision and speed, or if you require a robust system with minimal maintenance and a long operational life, a fiber laser is well suited for you. Still, always consider your specific material and application requirements,. Additionally, our experts are always happy to assist you in your decision-making process or answer any questions you might have. 

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