Fiber laser, diode laser and CO2 laser source are the three most common types of laser. CO2 laser source is easy to distinguish from them; because it is suitable for cutting/engraving non-metallic materials. Fiber and diode laser sources are suitable for cutting/engraving metallic materials.

You know the difference? Which laser source is the best choice if you want to start a laser engraving business?
If you need clarification about the differences and which business they are suitable for, you are not alone.
They have different operating principles, characteristics, pros and cons.
The differences between the two are discussed and compared in the following section.

CONTENTS

1. What is diode laser source and how does it work?
2. What is fiber laser source and how does it work?
3. Difference between fiber and diode laser source

What is diode laser source and how does it work

A diode laser (also DDL, injection ILD or laser diode) is an optoelectronic device, whose main principle is to convert electrical energy into light energy. Diode laser source works similarly to the LED, you may be familiar with LED lights.
Initially, diode lasers were used in products such as mice, laser pens, beam lighting and laser scanning. Later on, as technology progressed, diode lasers were gradually combined with optical components and then continuously improved so that the diode laser could now be used for cutting/engraving metal.

How does diode laser work?

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Main steps in generating the laser beam: light absorption, spontaneous emission, and stimulated emission.
The core of the diode laser is the p-n junction diode, where a voltage is applied at both ends of the diode, and electrons move from the N-type layers to the P-type layers (rich in "holes" or lack of electronics). This process is part of the movement of electrons from higher to lower energy levels and produces the emission of photons (also spontaneous emission).
This process is known as stimulated emission, where the emitted photons interact with the incident electrons to produce more photons, repeatedly making more light of the same phase, coherence, and wavelength.
The p-n junction diode of a diode laser is made of a gallium arsenide layer, followed by silicon, aluminum, and sun as dopants. The semiconductor material determines the wavelength of the emitted beam, which ranges from the ultraviolet (UV) to the infrared spectrum in our common diode laser.
The light generated is then passed through various optical elements such as reflectors and focal mirrors to gather the beam into a high-energy spot for fast engraving or cutting effects on the material.

What is fiber laser source and how does it work?

The Fiber laser (or fibre laser) is one of the most powerful and perfect cutting/engraving lasers. Like the diode laser, it is a solid-state laser.
It is also essentially a laser diode. Depending on the gain medium added, the wavelength produced by the fiber laser varies, generally between 780 nm - 2200 nm. The wavelengths vary depending on the industry in which they are used, with 1064 nm being the preferred wavelength for cutting sheet metal.

How does fiber laser source work?

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The Fiber laser differs from the diode laser in terms of the laser cavity.
The diode of a fiber laser is constructed from an optical fiber, the core of which usually consists of quartz glass and a dopant (ytterbium or erbium).
Positive and negative charges are released from the two poles and combine to form free electrons when they meet. The free electrons can only be released as photons, so when current flows through the semiconductor, the positive and negative charges combine in large numbers and the number of photons increases rapidly.
A special cladding refracts the resulting photons and enters the core, where they then follow their path.
The photons then enter the laser cavity, where they hit the doped fiber particles and interact with each other to produce more photons. This process is called electron excitation.
The doping element within the laser cavity determines the wavelength of the laser. For example, our commonly used fiber laser cutter is usually doped with ytterbium to produce a wavelength of 1064 nm.
The photons leaving the laser cavity form a beam of the same phase, coherence and wavelength.
This is how fiber laser works.
The laser beam is then passed through its optical components, such as a lens and a focusing mirror until the final laser can easily cut sheet metal.

Difference between fiber laser and diode laser

These are the working principles of fiber laser and diode laser. However, there may be more important differences for the user who is gonna buy a laser.
I will now discuss the differences regarding price, features, and applications.

Wavelength

The wavelength of the laser determines the type of material the laser is suitable for cutting/engraving and the range of applications. Although both fiber lasers and diode lasers are solid-state lasers, there is a difference.
The fiber laser has a fiber source and a wavelength of typically 1064 nm, which metals easily absorb. The fiber laser is undoubtedly the best laser for cutting/engraving metals.
The Diode laser does not have a fiber source, has a wavelength range of 550 nm - 950 nm, and is suitable for engraving non-metals and metals. However, its wavelength is not fully absorbed by the metal, which results in wasted energy when cutting.

Laser power

Laser power is not the same as machine power, and many vendors will publish false advertising to confuse customers with machine power. It is important to check the laser power of the laser cutter before purchasing.
The laser power determines the machine's ability to cut/engrave objects. Generally, higher power, the faster cutting speed and longer cutting depth.
The laser power of the diode laser is low, usually 2-20 watts. The metal does not completely absorb the wavelength of the diode laser, so the same power as the fiber laser has a much greater cutting capacity than the diode laser. And for less than 10 watts, the diode laser is only suitable for engraving metal materials; it is very difficult to cut metal.
The Fiber laser is the most powerful for both CO2 laser and diode laser. Typically it supports a wide range of power options from 20W to 15KW. For the same laser power, the fiber laser has about 10 times the cutting capacity of the diode laser.

Material flexibility

Although many vendors advertise that their diode laser engraver can easily cut/engrave metal. In fact, the diode laser has a very narrow engraving range for metal, and the cutting process is complicated. The engraving of metal can only leave very shallow marks.
The diode laser is most commonly used to engrave wood, plywood, leather, opaque acrylic, coated metal and marble.
If you want to start a small business and focus on engraving metal, there are better choices than the diode laser. A diode laser engraver is more of an engraving toy unsuitable for commercial use. If your main business requires non-metal engraving materials, then the CO2 laser cutter is recommended.
The fiber laser offers less in terms of material flexibility, and it is better suited for cutting/engraving metallic materials. It can easily cut/engrave various metal materials such as aluminum, gold, copper, stainless steel, carbon steel, ceramics, marble, etc.

Cutting speed

Another great advantage of the fiber laser is its high cutting speed. The fiber laser can cut up to 15% faster than the diode laser for the same laser power. However, the diode laser can engrave even quicker.
And laser power is proportional to speed. The higher the power, the faster the speed. Therefore, it is no exaggeration to say that the fiber laser has the highest cutting speed.

Cutting thicknesses

For cutting metal, there is no doubt that the thickness of the cut that the fiber laser can support is superior. Because the diode laser is suitable for engraving, it is not ideal for cutting materials.

Service life

The machine's lifetime is also important to consider when purchasing a machine. Fiber lasers have the longest lifetime, around 100,000 hours. The diode laser has a lifetime of about 20-50,000 hours.
Lifespan: fibre laser > diode laser > CO2 laser

Price

The production price of a diode laser is much lower than that of a fiber laser, so many businesses falsely advertise their diode laser as a fiber laser. For the same power, the production price of a fiber laser is about five times higher than that of a diode laser, and the price difference increases as the power increases.
Typically the 10 w diode laser engraver sells for between $500-$1000, and the 20 w fiber laser cutter sells for $1500-$3000.
However, the fiber laser cutter has a longer life span and more productive. If you want to start a laser business with a laser cutter,fiber laser cutter is the best choice.

Maintenance

Both are solid-state lasers, so both have low maintenance requirements. And as laser engraving does not touch the material, there is no loss during the engraving/cutting.
If the fiber laser damages any fibers during use, you have to replace the entire laser module.
The diode laser has no laser source, so you don't have to worry about damage to the fiber cable. Diode laser requires you to worry about the module overheating and the laser module burning up. If it does, the entire laser module will need to be replaced.

Conclusion

Fiber, diode and CO2 laser source are different in many ways. For the user, however, little attention is paid to how they work. Users are more interested in laser cutter's engraving material, speed and longevity.
Choose a diode laser cutter if you want to buy the laser for personal. Still, if you want to use the laser for small business or other commercial, I recommend you choose fiber laser cutter or CO2 laser cutter. How to  choose depending on your business needs.