We usually use MOPA lasers. A MOPA (Master Oscillator Power Amplifier) fiber laser is a type of laser system that has enhanced control over pulse durations and peak power, which provides precise processing capabilities on various materials.
MOPA fiber lasers are primarily designed for metal marking applications, including delicate or high-contrast marking. They can process a wide variety of metals and some plastics, but they are not ideally suited for materials like wood even though they can be cut, it often takes longer.
Fiber lasers, like MOPA fiber lasers, typically emit light at a wavelength of around 1,064 nanometers, which is in the infrared spectrum. On the other hand, CO2 lasers operate at a longer wavelength, typically 10,600 nanometers.
The ability of a material to absorb laser light (which is essential for cutting and marking processes) is influenced by the wavelength of the laser and the material’s optical properties.
For most metals, the shorter wavelength of the fiber laser light (1,064 nm) is absorbed more efficiently, making fiber lasers a great choice for metal marking or cutting. But for organic materials like wood, and many plastics, the longer wavelength of CO2 lasers (10,600 nm) is more effectively absorbed.
How do these lasers do on wood?
As for the properties of wood that might affect laser absorption, here are a few key factors:
- Color and Surface Condition: Darker woods tend to absorb more laser energy than lighter ones. Similarly, wood with a rough surface tends to absorb more laser energy than wood with a polished or glossy surface.
- Density and Hardness: Denser woods are generally harder to cut because they absorb less laser energy. The denser the wood, the more power you typically need to cut or engrave it.
- Moisture Content: Wood with a high moisture content can absorb some of the laser energy, making it more challenging to cut or engrave.
- Grain Direction: The direction of the wood grain can also affect how the laser energy is absorbed. Cutting along the grain can be different from cutting across it.
- Chemical Composition: The specific chemical composition of the wood, including the types of fibers, resins, and other substances present, can also affect absorption.
Each type of wood reacts a bit differently to the same laser settings due to variations in these properties. That’s why trial and error, combined with careful observation and record-keeping, is an important part of the process when you’re working with new materials or equipment.
What about metal?
Our lasers work great on metal. The underlying principles behind the absorption of light energy by different materials, including metals and wood, are rooted in their atomic and molecular structures. Let’s dive a little deeper into this.
The absorption of light by a material occurs when the energy of the incoming photons (light particles) is transferred to the electrons within the atoms or molecules of the material. This energy can excite the electrons to a higher energy state, or even cause them to be ejected from their atoms (as happens in the photoelectric effect). The extent to which a material absorbs light at a particular wavelength is determined by how closely the energy of the light matches the energy needed to excite the electrons in the material’s atoms or molecules.
Metals have a “sea of free electrons” that aren’t tied to specific atoms. These electrons can absorb a wide range of photon energies, meaning they absorb light across a broad spectrum, including the visible and infrared parts of the spectrum. This is why metals are generally shiny (they reflect a lot of visible light) and get hot quickly in sunlight (they absorb a lot of infrared light, which is then converted into thermal energy).
Wood, on the other hand, is primarily composed of organic compounds, which have more complex atomic structures than metals. The energy levels available to electrons in these compounds are more discrete and specific, meaning they absorb light strongly at some wavelengths and weakly at others. In the case of wood and many other organic materials, the absorption of light is strongest in the ultraviolet and visible parts of the spectrum, and weaker in the infrared.
However, the long wavelength of the CO2 laser (10,600 nanometers) is absorbed more effectively by wood than the shorter wavelength of the fiber laser (1,064 nanometers). The exact reasons for this difference are complex and depend on the specific molecular structures and vibrational modes of the molecules in the wood.
That’s a simplified explanation, but hopefully it gives folks some insight into the atomic and molecular aspects of how different materials absorb light. These absorption behaviors play a key role in determining which types of lasers are best suited for processing different materials.
QC Lightbeam is your local expert company for metal laser processing and laser engraving in the greater Quad Cities area of Iowa and Illinois.
Types of Lasers
| Type of Laser | Wavelength (nanometers) | Wavelength Range | Typical Applications |
|---|---|---|---|
| UV Lasers | Around 355 | Ultraviolet | Micro-machining, micro-electronics fabrication |
| N/A | 400-700 | Visible Light | Visible to the human eye |
| Nd:YAG Laser | Around 1,064 | Near-Infrared | Welding, cutting |
| Fiber Laser (e.g., MOPA) | Around 1,064 | Near-Infrared | Marking or engraving metals, some types of plastic |
| CO2 Laser | Around 10,600 | Far-Infrared | Cutting and engraving wood, plastic, glass, some types of metal |
UV Lasers: These lasers operate in the ultraviolet range, typically around 355 nm. They are often used in applications requiring very high precision, such as micro-machining and the fabrication of micro-electronics.
Green Light: For reference, the wavelength of green light is approximately 532 nm.
Nd:YAG Laser: This type of laser operates at a wavelength of approximately 1,064 nm, in the near-infrared range. Nd:YAG lasers are used in many industrial applications, including welding and cutting.
Fiber Laser: Like Nd:YAG lasers, fiber lasers also typically operate at around 1,064 nm. MOPA fiber lasers fall into this category. They are often used for marking or engraving metals and some types of plastic.
CO2 Laser: This type of laser operates at a wavelength of approximately 10,600 nm, in the far-infrared range. CO2 lasers are commonly used for cutting and engraving a wide range of materials, including wood, plastic, glass, and some types of metal.