How do you dial in frequency and pulse width on a MOPA laser?
On a diode, speed and power are the whole game. A MOPA fiber laser hands you two more dials. Guess at MOPA laser frequency and pulse width (LightBurn calls pulse width Q pulse) and a good speed and power setting still comes out scorched.
Applies to
- Process
- MOPA fiber lasers (galvo)
- Not for
- Diode lasers; Q-switched fibers have frequency only
- Software
- LightBurn galvo Material Test
Why it matters
Frequency is how many pulses the laser fires per second. Pulse width is how long each one lasts. Change either and you change how the energy lands on the material, even at the same speed and power.
That’s why you test them separately. Sweep all four at once and you can’t tell what caused what.
When Steve Makes Everything ran his second grid on matte acrylic, a good chunk of it was way too much. The clean cells sat around 20 for frequency and 130 for Q pulse.
What good looks like
- Speed and power were locked from an earlier test before frequency and pulse were touched
- The test sweeps exactly two things: frequency and Q pulse
- The winner holds up on a detailed image engrave
- All four values are saved together for that material
How to apply it
- Run a speed/power material test and narrow it until one setting wins.
- Save that speed and power into the material test’s settings, so every cell uses them.
- Change the test’s two parameters to frequency and Q pulse.
- Run it, skip the overcooked cells, and pick the cleanest.
- Confirm on a real image engrave, then save speed, power, frequency and pulse width to your library.
Exceptions & tradeoffs
Diode users can skip this page. Steve says it straight: speed and power are the settings a diode has.
A standard Q-switched fiber has a fixed pulse width, so you only test frequency. The pulse width dial is a MOPA thing.
Steve’s numbers are for his 60 W ComMarker on matte acrylic. Treat them as a sense of scale, not your settings.
Common mistakes
- Testing frequency and pulse before speed and power are setLock speed and power first
- Sweeping speed, power, frequency and pulse in one gridTwo parameters per test
- Copying someone’s MOPA settings onto a different wattageRun the frequency/pulse test on your machine
Frequently asked questions
- What frequency and pulse width should I use on a MOPA laser?It depends on the material and machine. Find speed and power first, then test frequency against pulse width. On 3 mm matte acrylic, Steve Makes Everything landed near 20 and 130 on a 60 W MOPA.
- What is Q pulse in LightBurn?It’s the pulse width setting for MOPA fiber lasers: how long each laser pulse lasts, in nanoseconds.
- Do diode lasers have frequency or pulse settings?Not in this sense. On a diode, speed and power are the settings that matter, with line interval as a per-job tweak.
- Can LightBurn’s material test vary frequency and pulse width?Yes. Change the test parameters to frequency and Q pulse, and keep speed and power fixed.
Frequency and Q pulse as fiber-only settings a diode user can skip — Your Laser Settings Are a Hot Mess! Here's the Quick Fix! ↗ at 02:22.
Locking speed and power, then switching the material test to frequency vs Q pulse — Your Laser Settings Are a Hot Mess! Here's the Quick Fix! ↗ at 05:24.
The result on matte acrylic: frequency around 20, Q pulse around 130 — Your Laser Settings Are a Hot Mess! Here's the Quick Fix! ↗ at 06:05.
The two-stage approach and the 20 / 130 result are Steve Makes Everything’s, on a 60 W ComMarker MOPA. The Q-switched note and the kHz / ns units are standard fiber-laser background I added so the numbers mean something.