Your Guide to Understanding Laser Powers

The applications for laser technology are numerous and span many sectors, including automotive, medical, and aerospace. If you’re new to laser applications, you might wonder which type of laser equipment will work best for you.

Naturally, you might look at the specifications and assume that more is automatically better. However, understanding the context of these specifications is of the utmost importance.

A prime aspect to look for while comparing lasers is laser power. What does a power of 100 watts mean? Is 30 Watts better than 25 Watts? To know the answers, you need to understand how laser power impacts laser marking and processing applications.

In the following, we’ll explore the fundamentals of laser power and how to optimize laser technology for precision and accuracy. This will help you choose the right equipment for your specific needs.

Laser Powers in Industry-Specific Applications

Before we get into the details of laser power, we must recognize that laser powers vary significantly based on their intended use.

The power of a laser source affects weld strength, cutting speed, marking contrast, engraving depth, and the heat-affected zone, among other factors.

For instance, a laser marker used for precise engraving on delicate materials may operate at a much lower power than one used for cutting thick metal sheets. Similarly, higher laser powers are typically required for welding thicker materials or achieving deeper weld penetration in the manufacturing industry.

Beyond laser welding and engraving in manufacturing, laser power has contributed significantly to the medical and aerospace industries. In the medical field, for example, power is needed to get dark contrast for easily readable marks; however, too much power can damage the surface, rendering it useless. In aerospace applications, higher power is often used for faster processing speeds or when applying thicker clad layers. The versatility and effectiveness of laser power make it a sought-after tool across many sectors.

Key Laser Power Parameters

Laser parameters can be modified to determine how the power of a laser can be used. Here are a few key parameters you should know.

Pulse Energy

The energy produced by a single laser pulse is referred to as pulse energy. If your specific application requires a UV laser marker with less energy, you can modify this parameter to get the desired results. Consider a scenario where a UV system with a 355 nm wavelength, operating at just 2.5 Watts, outperforms a 50 W fiber laser at 1090 nm wavelength on various plastics. The shorter wavelength provides a faster mark and better quality, highlighting that pulse energy isn’t just about power.

Pulse Duration

Pulse duration, or pulse length, signifies the amount of time the laser emits a pulse. A shorter pulse means the peak power is high. This parameter matters most in applications where precise timing is needed, such as laser surgery or spectroscopy.

Regardless of wattage, pulse duration can significantly impact the efficiency of the marking process. For example, a high-power laser marker at 100 W with a pulse duration of 10 ns has a less intense pulse than a 25 W marker with a shorter pulse duration of 5 ns. The shorter pulse allows for more precision and detail.

Pulse Repetition Rate

The pulse repetition rate indicates how frequently pulses are emitted per unit of time. It’s often expressed in kilohertz (kHz) or hertz (Hz). It’s crucial in applications needing continuous processing, such as UV laser marking, cutting, or welding. You can use a high-power laser when more pulses per second are required. For example, a 100 W laser can release 100,000 pulses of 1 MJ per second. But one thing to note is that if you need to increase the number of pulses, you must lower the pulse energy.

Spot Size

Laser energy can be distributed unevenly as laser beams can have different shapes. So, spot size refers to the diameter of the laser beam where its intensity is most focused. A smaller spot size means higher energy peaks, so if you’re undergoing a process like laser etching and need to go deep into the material, a small spot size will work well.

Although a larger spot size covers a bigger surface, it sacrifices detail and precision. For example, a 50 W laser marker with a 100 µm spot size won’t achieve the same speed and accuracy as a 25 W marker with a smaller spot size of 50 µm.

Choosing the Right Laser Pulse Energy: Pulsed vs. CW Lasers

One significant consideration when using lasers is whether to use continuous or pulsed laser power. Both types use their available power differently.

CW Laser

A CW laser (continuous-wave laser) emits a continuous beam of light, providing a constant power output. For example, a 50 W CW laser consistently releases 50 joules of energy per second. They are ideal for applications requiring a steady energy delivery, such as laser cutting or welding thick materials.

Pulsed Laser

A pulsed laser, on the other hand, delivers energy in pulses with brief pauses. These breaks allow the laser a chance to gather more energy before shooting out the next burst. Because of this, a pulsed laser can hit higher energy levels compared to a CW laser.

Distinguishing

To help you understand beam laser power, it’s important to know the difference between average power, laser peak power, and power density. Let’s break down these concepts

Average Power

Average power is commonly interchanged with laser power. It’s the total energy a laser delivers in one second. A 100 W laser has an average power of 100 W, no matter whether it’s continuous or pulsed. Average power is essential for assessing the overall performance and energy consumption of a laser system.

Laser Peak Power

Laser peak power is the highest laser power output a laser can achieve in a given amount of time. To calculate peak power, you just divide the pulse energy (measured in joules) by the pulse duration (measured in seconds). For instance, if you have a 1-millijoule pulse lasting 100 nanoseconds, the peak power would be at least 10,000 watts.

Laser Power Density

Power density, also called irradiance, tells us how much energy is packed into a given area. It’s measured in watts per square centimeter, showing how quickly energy is transferred within a specific space.

To find the power density, you simply divide the laser power by the size of the beam. The power density of a beam plays a significant role in marking and processing quality and speed. As you can imagine, even a “lower power” laser can often mark, cut, or engrave faster than a “higher power” system if its beam spot is smaller, which improves laser power density.

Conclusion

When it comes to laser power, a simple principle applies: more isn’t always better. While it’s easy to assume that a higher average power is the ultimate goal, blindly pursuing it can be counterproductive. If a higher average power comes at the cost of a lower peak power, reduced power density, or a longer pulse duration, it may cause more harm than good for your specific application.

The key to choosing the right laser power lies in understanding the interplay between different parameters and making informed trade-offs based on your unique application needs.