Powering CO2 and Semiconductor Lasers

Both CO₂ and semiconductor lasers create concentrated beams of light, usually used for cutting away material, but they work in drastically different ways. They generate power through two different mechanisms, and each type of laser can come in diverse subtypes and configurations. Still, both processes start with reliable electrical power delivered from a sophisticated power supply.

Let's explore the mechanisms behind CO₂ and semiconductor lasers and what you'll need to power them.

What Is a CO₂ Laser?

A CO₂ laser uses carbon dioxide (CO₂) as its lasing medium. This gas creates a highly focused beam of light that can cut, mark, engrave, weld, and solder different materials. While CO₂ is the primary "ingredient," CO₂ lasers also contain nitrogen and helium to support the process.

These lasers can reach up to 6 kilowatts (kW) of power, depending on the application. Working with harder materials like metals generally requires a more powerful laser. CO₂ lasers can also vary in operating wavelength, either 10.6 micrometers or 9.6 micrometers.

You'll find these lasers used in many industries, including:

• Manufacturing: The precision and power of these lasers make them a good fit for cutting and shaping materials for manufactured products, such as auto parts, packaging and textiles.
• Fashion: CO₂ lasers are also used for distressing fabrics (particularly garments made with denim )
• Surgery: Surgeons sometimes use advanced CO₂ lasers for precise ablation with minimal risk to nearby tissue.

Like many other lasers, you can use a CO₂ laser in continuous or pulse mode. As the names imply, a continuous laser stays on, while a pulsed laser creates multiple pulses of light at high peak power. Continuous lasers often support smooth marks or cuts on relatively soft materials, while pulsed lasers can offer more concentrated power for improving edges and cutting through stronger materials.

How Are CO₂ Lasers Powered?

Creating heat and light from the CO₂ mixture starts with the process of excitation, which gives the gas mixture more energy. The gas mixture includes nitrogen because exciting nitrogen allows it to transfer its extra energy to nearby CO₂ molecules, offering more efficiency than if you excited the CO₂ alone. The gas is stored in a sealed tube with mirrors on either side. One of the mirrors offers full reflection, but the other allows some light to move through it.

Applying electromagnetic waves to the gas mixture excites the molecules so they reach a higher-energy state. As the molecules gain enough energy, they emit light. The reflective mirror helps reflect the light to encourage further excitation. When the light is bright enough, it moves through the partially reflective mirror. This mirror serves as the output to guide the light toward the item being cut or engraved.

This entire process starts with electricity, usually a direct current (DC) power supply. Depending on the laser, these sophisticated power supplies can draw power from the building's normal electrical supply.

What Is a Semiconductor Laser?

A semiconductor laser is also called a diode laser. Rather than using gas, it uses a semiconductor material, such as gallium arsenide (GaAs) or zinc sulfide (ZnS). Possible excitation methods include electric injection, electron beam excitation and optical pumping.

Diode lasers are more common than CO₂ lasers because they can be very small, so they're used in everything from barcode scanners to laser printing. You can also achieve more power — up to several kilowatts — with semiconductor lasers by stacking them and combining the beams. Other applications include:

• Metal welding
• Laser pointers
• Laser scanners
• Fiber optic communications
• Disc-reading and -recording systems
• Medical treatments and procedures

The selected semiconductor material will determine the beam's wavelength, ranging from infrared to ultraviolet (UV). Some diode lasers can run continuously, while others must use pulse mode.

How Are Semiconductor Lasers Powered?

Like a CO₂ laser, semiconductor lasers depend on the excitation of molecules, but the process is different. It uses a p-n junction diode that works like other diodes. It sandwiches a space between two pieces of treated material — a p-type and an n-type. The p-type is a material with slightly too few electrons, while the n-type has slightly too many. When an electric current flows between these two pieces, they create photons.

A semiconductor laser uses alloys like gallium arsenide and indium gallium arsenide phosphide in the diode. It generates photons with incoming electrons, which interact with each other to create even more photons. Similar to the mirror in a CO₂ laser, a diode laser amplifies energy by allowing the molecules to bounce around. It uses a Fabry-Perot cavity, a microscopic junction between the diodes where the photons bounce around and gain energy until they're ready to leave the junction.

Semiconductor lasers also start with basic electrical energy. They often connect to a building's electrical supply through the wall, but due to their small size, some can be powered through batteries for handheld devices.

Semiconductor Lasers vs. CO₂ Lasers

Both lasers perform well in different environments. Semiconductor lasers are a cost-effective, compact option for electronics manufacturing, printing and engraving operations. If you need something more powerful, such as for cutting metals or glass, you will need a CO₂ laser.

CO₂ lasers are understandably large and will take up considerable space. The components, such as precisely placed mirrors and a large glass tube, can also be fragile. They cost more than diode lasers and include expenses for operator training and installation. Many users find these drawbacks well worth it for benefits like:

• More power: A CO₂ laser can achieve much higher power than a diode laser. It offers higher wattages and quickly cuts through hard materials.
• More versatility: With this increased power, CO₂ lasers can work with more items and provide flexibility.
• High precision: The precise cutting power of a CO₂ laser allows you to meet stringent requirements, including medical applications and the production of parts with strict tolerances.

Diode lasers are best suited for low-energy applications, and many hobbyists use them. Commercial applications include engraving and cutting soft materials like leather and paper. You'll also find them in packaging and other high-volume printing operations. Although they aren't as powerful and have limited applications, a diode laser can offer these benefits:

• Small size: Their compact size makes semiconductor lasers much more approachable and easy to incorporate into your workflow.
• Cost: Diode lasers are more cost-effective upfront, and they're more durable, so they can be moved around easily.

The right one for your operation will primarily depend on what you're trying to do and how much power you need.

Using the Right Power Supply for CO₂ and Semiconductor Lasers

Whichever type of laser you get, you'll need a well-controlled flow of power. Fluctuations in the electric current can cause interruptions and potentially damage these sensitive tools. A precise, reliable power supply can ensure efficiency and prevent interruptions.

At Astrodyne TDI, we've been designing cutting-edge power solutions since the 1960s, so our laser power supplies benefit from decades of expertise. Our liquid-cooled power supply supports up to 16.5 kW of power in a compact, high-efficiency unit. It offers a wide-range, fully adjustable DC output you can configure from a digital interface. Learn more about the Kodiak power supply online, or request a quote today!

If you're not sure which power supply is suitable for your laser, reach out to our knowledgeable team for more information.