Laser Material Compatibility Guide

Critical Safety Information

Quick Decision Guide

Complete Compatibility Matrix

Click any category name or material cell to see detailed shop reality and physics explanations. Categories are collapsible - expand the ones you care about.

Understanding CO2 Laser Tubes: Glass vs RF

You'll see CO2 lasers advertised with either glass tubes or RF tubes, usually about $1,000 price difference. They both produce the same 10.6μm wavelength, so material compatibility is identical. But the performance gap is real.

Glass Tubes (DC Excited)

Glass tubes use electrodes at each end to excite the CO2 gas. Cheap to manufacture, cheap to replace. The OneLaser XT is a solid example. 55W glass tube machine that'll handle most hobby projects fine.

Why they wear out faster: Those electrodes are in direct contact with the gas. Over time, they degrade and contaminate the gas mix. You'll notice it when your cuts that used to work at 80% power now need 90%, then 95%, then don't cut all the way through anymore.

Why beam quality suffers: As the gas gets contaminated, the beam gets less consistent. You'll see variations in cut depth across the bed. A fresh tube cuts clean, but six months later you're fighting it.

Practical reality: Glass tubes need 3-5 minutes to warm up before they're stable. Power output drifts during long jobs. But for $200-300 replacement cost every 2,000-8,000 hours, it's manageable.

RF Tubes (Radio Frequency Excited)

RF tubes excite the gas with radio frequency energy through metal plates. No electrodes touching the gas. The OneLaser XRF uses a 38W RF tube and costs about $1,000 more than the XT.

Why they last longer: No electrode degradation means the gas stays pure. Power output on hour 30,000 looks the same as hour 1. Settings you dialed in three years ago still work.

Why beam quality is better: RF tubes maintain tighter beam focus because the gas stays clean. You get more consistent power density across the beam profile, which means cleaner edges on fine detail work.

Why they're better at detail: Two reasons. First, RF tubes are more compact (same power in 1/3 the length), so the beam path is shorter and more stable. Second, instant-on operation means no thermal drift during warmup. You can start cutting intricate detail immediately.

Practical reality: Instant on. No warmup. Power stays consistent during 8-hour production runs. But at least $1,000+ to replace if you ever need to (most people don't).

Which Should You Get?

Hobby use: Glass tube saves you money upfront and $200-300 replacement tubes are no big deal. The XT-style machines work great for weekend projects.

Side business: RF if you can swing it. Consistent power matters when you're making the same product repeatedly. Nothing worse than redoing settings every few months as the tube ages.

Full-time business: RF tube, no question. The extra $1,000 pays for itself the first time you don't have to stop mid-job because the tube died. And the detail quality difference is real if you're doing fine work.

Understanding Fiber Laser Types: MOPA vs Standard

You'll see fiber lasers advertised as either standard or MOPA, usually $3,000-5,000 price difference. Both produce the same 1.064μm wavelength, so material compatibility is identical. But MOPA gives you control over pulse characteristics that standard fiber locks in at the factory.

The question is whether you actually need that control.

Standard Fiber Lasers

A standard fiber laser uses a seed laser diode that shoots light into a fiber optic cable doped with rare earth elements (usually ytterbium). The fiber is coiled up, and as light bounces through it, the ytterbium atoms get excited and amplify the light. By the time it exits, you've got a powerful, focused beam at 1.064μm.

The beam gets pulsed using Q-switching (basically turning it on and off very rapidly to create high peak power). But the pulse characteristics are fixed. Whatever pulse width and frequency the manufacturer designed in, that's what you get. Most desktop units are around 100-200 nanosecond pulses at 20-80 kHz.

What this means in practice: You mark metal fast. Stainless, aluminum, brass, titanium all clean, permanent marks. You control power and speed, and that's it. Simple. Reliable. Marks are black or dark grey depending on the metal.

Limitations: Can't do color marks. If you want to vary depth in a single pass, you need multiple passes at different power levels. Less control over heat input means larger heat-affected zones on delicate work.

Cost: $2,000-6,000 for 30-50W desktop units. The standard for metal marking.

MOPA Fiber Lasers (Master Oscillator Power Amplifier)

MOPA splits the laser into two stages. The master oscillator creates the initial pulse, and you control its characteristics (pulse width from 2 nanoseconds to 500 nanoseconds, frequency from 1 kHz to 4000 kHz, even kill the first pulse entirely if you want). Then the power amplifier boosts it.

Why pulse control matters for color marking: When you hit stainless steel or anodized aluminum with controlled pulse widths, you create oxide layers of different thicknesses. Thin oxide = grey. Thicker = yellow, red, blue, purple. It's like anodizing titanium, but done with the laser. Standard fiber's fixed pulse can only do black.

Why it helps with fine detail: Shorter pulses (2-20ns) dump less total energy into the material. Less heat spread means cleaner edges on tiny features. If you're marking serial numbers on watch movements or intricate patterns on jewelry, you'll notice the difference.

Variable depth capability: You can adjust pulse width mid-job. Start with 200ns for deep engraving on part of a design, drop to 20ns for fine surface detail on another part, all in one pass. Standard fiber needs you to run the job multiple times at different power settings.

Cost: $5,000-12,000 for 30-60W desktop units. About 2-3x the cost of standard fiber.

Which Should You Get?

Metal marking and engraving: Standard fiber handles 90% of jobs. Serial numbers, logos, deep engraving, cutting thin sheet all covered. Save the money.

Color marking is required: MOPA. If clients are specifically asking for colored marks on stainless or anodized aluminum, you need it. Standard fiber physically can't do colors.

Fine jewelry or electronics work: MOPA's shorter pulses give cleaner results on tiny, delicate features. Worth considering if that's your market.

Honest take: I bought MOPA thinking I needed color marking. Used it twice in two years. For most shops doing part marking, product branding, or general metal engraving? Standard fiber is plenty. Buy that, save $3-5K, upgrade later if color work actually materializes.

Understanding Diode vs CO2 for Wood Engraving

Here's something nobody tells you: diode lasers make DARKER engravings on wood than CO2 lasers. Not faster, not cleaner—just darker. Way darker.

I ran the same photo engraving test on birch plywood with a 20W diode and a 60W CO2. Same image, optimized settings for each laser. The diode engraving looked like it was printed with black ink. The CO2 version had depth and detail, but the blacks were more brown-char than pure-black.

The Physics Behind It

Diode (445nm) at ~500°C:

• Wood surface heats to pyrolysis temperature (thermal decomposition)
• Cellulose and lignin break down into simpler molecules
• Carbon stays on the surface while volatiles (water, CO, CO₂) evaporate
• Surface carbon content climbs from wood's normal 27% to 93%
• You're left with a 0.01-0.05mm thick layer of nearly pure carbon
• That carbon layer is visible as deep black—like graphite

CO2 (10,600nm) at 4,000-10,000°C:

• Material hits ablation temperature in microseconds
• Everything vaporizes—carbon included
• Gets blown away by air assist before it can accumulate
• You get a clean void with measurable depth (0.5-2mm possible)
• The brown you see is char from edges where temp wasn't quite hot enough to vaporize

What This Means in Practice

Dark wood like walnut: Diode creates blacks that look like ink. CO2 creates depth. Both work from the first pass because dark wood has lignin and tannins that absorb light efficiently (60-70% absorption).

Light wood like birch: Diodes are painfully slow at first. The first pass barely leaves a mark because light wood reflects most of the 445nm wavelength (only 10-15% absorption). You're charring your way in over 15-20 passes until you build up enough black carbon to really absorb light. Once that char layer forms (now 50-80% absorption), subsequent passes work faster. CO2 does the job in 2-3 passes because it's just removing material.

Photo engraving: If you need maximum black for high-contrast photos, diode wins. The blacks are pure carbon—darker than anything CO2 can produce. But it takes 10-15x longer to engrave the same image.

Which Should You Use?

For speed and cutting: CO2, no question. Cuts through carbonization and vaporizes material efficiently. Can handle thick materials and production work.

For darkest blacks in photos: Diode. The carbonization layer creates pure black that looks like printer ink. Perfect for portrait engravings and high-contrast artwork.

Honest take: I keep both. I've had customers send back CO2-engraved plaques asking why the photos look "washed out" compared to samples they saw online (which were probably diode-engraved). Now I set expectations: CO2 gives you depth and speed, diode gives you pure black but takes forever.

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