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The Science Behind Fiber & CO2 Lasers

Key Differences Explained

In industrial applications, two types of lasers are most widely used: CO₂ and fiber lasers. The former have long been common in cutting and engraving of various materials, from metals to plastics. Fiber lasers, however, took the usability, accessibility, and efficiency of laser material processing to a new level in recent years. This blog dives into the key differences between the two laser types, exploring the science behind each as well as their standing in today’s demanding industrial settings.

The Science

Yb-Doped Fiber
CO₂ as Lasing Medium

Efficiency

Metal Reflectivity
Concentrated Light Beam Size
Electricity Conversion Rate

Short Pulse Mode
Mobility
Power
Applications

High Precision Machining & More With Fiber Lasers
Plastics, Ceramics, Metal & Soft Tissue With CO₂ Lasers

Outlook

The Science

A fiber or CO₂ laser system produces a concentrated beam of light in the infrared region of the electromagnetic spectrum. Focused on a surface, the beam’s thermal impact vaporizes material in a process of ablation. By defocusing the beam and extending the processing, the microstructure of the material can be altered through annealing or melting. This technology became useful in a wide range of manufacturing applications, including cutting, engraving, marking, drilling, cleaning, welding, texturing, and polishing.

Yb-Doped Fiber

Different types of fiber lasers used in specific environments today are doped with rare earth elements as the gain medium. Fiber laser systems designed by Laser Photonics integrate lasers with ytterbium (Yb) ions. Energy is supplied to a Yb-doped optical fiber through light pumping using semiconductor laser diodes. The light excites Yb ions and they discharge, emitting near-infrared photons. In turn, this leads to the excitement of more Yb ions and the release of new photons of the same wavelength in a process of stimulated emission. This stimulated light amplification effect is known as lasing.

Source: en.openei.org [27]

Ytterbium is a highly efficient doping medium for a number of reasons. For one, photons directly excite Yb-doped fiber, without any extra steps that could lead to energy loss in the process. In addition, the difference between the wavelength of light particles pumped by electrical energy and the output wavelength of Yb-doped fiber is relatively small. This means that most of the pumped energy input is converted into infrared light, while only a small percentage is lost.

CO₂ as Lasing Medium

In a CO₂ laser, carbon dioxide is the primary gas in the gain medium that also includes other substances, such as nitrogen (N₂), helium (He), oxygen (O2), hydrogen (H₂), and/or xenon (Xe). Similarly to stimulated emission in a fiber laser, an electrical discharge excites the particles of CO₂. Excited electrons collide with and excite the particles of other gases, losing some energy in the process. In turn, excited particles of other gases boost CO₂ particles to higher energy levels in a process of population inversion. Far-infrared light that CO₂ lasing produces cannot be delivered by a fiber cable. Generated inside a linear tube made of rigid materials like aluminum, quartz, or ceramics, far-infrared photons are deflected by a set of mirrors to the output optics, where the beam is focused and released.

Efficiency

Metal Reflectivity:

Fiber lasers emit light at a wavelength of 1064 nanometers (nm), compared to the 10.6-micrometer (µm) emission wavelength by a CO₂ laser. Metals have a significantly higher reflectivity rate against 10.6-µm photons. The more light is reflected off a surface, the less is absorbed, meaning it will have less impact on a surface. For example, aluminum absorbs seven times more radiation from a fiber laser than from a CO₂ laser. When heated, metal loses some of its reflectivity; nevertheless, a fiber laser is significantly more effective at processing metals than a CO₂ laser with the same power output.

Concentrated Light Beam Size:

Because of its smaller wavelength (1.06 < 10.6 µm), a fiber laser’s beam can be focused into a fine spot that’s 10 times smaller than a CO₂ laser’s. This means the power density in a focused laser spot of a fiber laser beam is significantly higher – and it is more precise, hence more efficient in fine-point, narrow-kerf, high-speed, and high-impact material processing. This also makes fiber lasers better suited for thinner materials.

Electricity Conversion Rate:

A fiber laser converts up to 42% of electrical energy input into laser light, compared to a CO₂ laser’s 10-20%. This means that CO₂ lasers consume more electrical energy to match the power output of fiber laser tools. That is why fiber laser systems are substantially more energy-efficient and cost-effective for various applications.

Short Pulse Mode

A fiber laser is capable of producing pulses that are significantly shorter and reach higher peak power (reaching gigawatts (GW) per pulse) than the pulses a CO₂ laser can produce. This makes fiber laser systems effective in applications that require ultra-short (picosecond or femtosecond) pulses.

For example, this method is used in stealth dicing of brittle, hard materials like silicon in die singulation. Ultra-short laser pulses would first create layers of micro-cracks under the surface of the material along the dicing line. Thermal or tensile stress would then be applied to easily separate the material, generating clean edges with no kerf loss and maximum yield.

Short pulse mode is also useful in processing materials with high heat sensitivity. A lower heat affected zone translates to less residual stress, minimal distortion and substrate damage, lower oxidation, and higher precision.

Mobility

Fiber lasers made possible the mobility and handheld operation of laser tools. In a CO₂ laser system, the laser beam’s optical path is limited to straight lines, guided by a series of mirrors to the cutting head and out onto the workpiece. By contrast, the fiber optic cable in a fiber laser system works as a flexible delivery path from the source to the scanhead.

Laser Photonics’ flagship CleanTech brand offers a wide variety of handheld, transportable laser cleaning tools for fieldwork or easy maneuvering around the warehouse. These are significantly more compact than any CO₂ laser machine.

Power

Another advantage of fiber lasers over CO₂ lasers is the greater affordability of high power fiber lasers. The power outputs of CO₂ laser machines, depending on their industrial or consumer purpose, range from 25 to 400 watts (W), with the vast majority below the 100-watt mark. Meanwhile, fiber lasers are increasingly built to be more powerful. A laser system on a U.S. Navy warship can be armed with a fiber laser ranging anywhere from 60 kilowatts to 300 kilowatts (kW).

Non-military-grade systems for material processing typically have no need for extreme power levels, but high-power options for speedier operations are becoming available – and adopted – across the industrial sector as well. A heavy-duty fiber laser machine for cutting thick metal, such as 30-millimeter (mm) steel, may come with a power output of up to 20 kW.

On the low-power end of the range are fiber laser marking and engraving systems. A compact MSCM-1010 for marking 4-square-inch designs sports a power output of 20 W. In this space, CO₂ lasers are still quite competitive in cost and versatility, as the low-power systems are affordable and effective in marking, engraving, and etching materials including glass, wood, leather, acrylic, and various plastics. On the other hand, fiber lasers of the same power output are considered more environmentally friendly due to their higher electricity conversion rate.

Applications

High Precision Machining & More With Fiber Lasers

Fiber lasers are widely used in industrial operations that involve cutting, cleaning, drilling, marking, engraving, texturing, drying, cladding, and welding of metals and nonmetals. Their precision also makes them particularly useful in the production of miniature devices, such as medical technology, pharmaceuticals, PCBs, and semiconductors – as well as in incision and photostimulation procedures like surgery.

Plastics, Ceramics, Metal & Soft Tissue With CO₂ Lasers

CO₂ laser machines are used in processing polymers, composites, metals, ceramics, and more. This includes applications such as busbar stripping, cutting and etching of acrylic or glass for interior design, sintering of plastics in additive manufacturing, pharmaceutical tablet drilling for time-release medications, and cladding of ceramic coatings for reinforcement. In addition, due to their high absorption rate by water, CO₂ lasers are frequently used in dermatological treatments and other medical procedures.

Outlook

Today, advancements in laser technology continue to increase the effectiveness, operational simplicity, and accessibility of laser-powered systems. Handheld machines are becoming more compact, while standalone systems are becoming smarter with the addition of robotics, machine vision, and artificial intelligence.

Further, innovative methods of managing the thermal impact of laser light are reducing the risk of overheating and improving the stability of the process. This means improved ability to achieve tight tolerances and a broader application spectrum for laser technology.

Engineers at Laser Photonics are constantly developing and implementing new technologies to create turnkey laser systems for effective material processing. We offer a comprehensive range of fiber and CO₂ laser-powered solutions in various configurations, customized to best suit your unique production environment.

Curious about how fiber and CO₂ lasers could improve your operations? Let’s talk!

The Science Behind Fiber & CO2 Lasers

Key Differences Explained

The Science

Efficiency

Short Pulse Mode

Mobility

Power

Applications

Outlook

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