Podczas porównywania CO₂ fractional laser machines, buyers often see specifications such as 200 μs pulse width, 20 mJ energy, 0.2 mm spot size, and 40W laser power. But what do these numbers actually mean—and which ones really matter when evaluating a machine?
Pulse width, spot size, laser source, and scanner performance are all important parts of evaluating overall machine quality. If you are comparing complete systems, start with our How to Evaluate a CO₂ Fractional Laser Machine: 4 Key Things to Check guide, which explains the RF laser source, pulse control, spot quality, and galvanometer scanner.
For clinic owners, distributors, and aesthetic professionals, understanding the individual parameters can help you look beyond the specification sheet. Pulse width affects how quickly laser energy is delivered, mJ describes the energy delivered per pulse or defined output event, and spot size determines how concentrated that energy is over a small area.
The important point is that these specifications should not be evaluated separately. A higher mJ value, shorter pulse width, or smaller spot size does not automatically mean a better CO₂ laser.
In this guide, we explain μs, mJ, and 0.2 mm spot size in simple terms, how they work together, and what you should actually check when comparing CO₂ fractional laser machines. After understanding these parameters, you can use our 5 Tests to Check a CO₂ Fractional Laser Machine Before Buying guide to see how spot quality, scanning accuracy, and output consistency can be checked on an actual machine.
Quick explanation:
μs = pulse duration
mJ = pulse energy
mm = focused spot size
Understanding these three numbers is the first step toward evaluating the actual output quality of a CO₂ fractional laser—not just its advertised specifications.
1. What Is Pulse Width?
Szerokość pulsu is the amount of time a single laser pulse lasts.
CO₂ laser pulse duration may be expressed in:
μs (microseconds) Lub ms (milliseconds).
The conversion is simple:
1,000 μs = 1 ms
Na przykład:
| Szerokość impulsu | Equivalent |
|---|---|
| 100 μs | 0.1 ms |
| 200 µs | 0.2 ms |
| 500 μs | 0.5 ms |
| 1,000 μs | 1 ms |
If a CO₂ laser specification says:
Pulse Width: 200 μs
it means that particular pulse lasts approximately:
0.0002 seconds.
That is an extremely short period of time.
2. Why Does Pulse Width Matter in a CO₂ Laser?
Pulse width is more than just a time specification.
It affects how quickly laser energy is delivered and how much time heat has to spread into surrounding tissue.
Consider two laser pulses with the same total energy:
Pulse A: 10 mJ / 200 μs
Pulse B: 10 mJ / 1,000 μs
Both deliver 10 mJ of energy, but they do not deliver it over the same period.
Pulse A delivers the energy over a shorter time.
Pulse B distributes the same amount of energy over a longer time.
Under otherwise comparable conditions, a shorter pulse can concentrate energy delivery into a shorter interval and reduce the time available for lateral thermal diffusion.
This is why two concepts are frequently discussed in CO₂ laser treatments:
Ablation — removal or vaporization of tissue
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Thermal Effect / Coagulation — heating of tissue surrounding the ablated area.
A well-designed CO₂ laser system needs appropriate control of both effects rather than simply producing as much heat as possible.
3. Does a Shorter Pulse Width Always Mean a Better Machine?
No.
This is an important distinction when comparing CO₂ fractional laser machines.
A short pulse duration can be useful for delivering energy rapidly and controlling thermal diffusion, but the final laser-tissue interaction also depends on other parameters, including:
Pulse energy, spot size, density, spacing, scan pattern, repetition, and number of passes.
Therefore, it would be too simplistic to say:
200 μs is always better than 500 μs, and 500 μs is always better than 1,000 μs.
For equipment buyers, a better question is:
Can the machine reliably control pulse duration and energy for different operating requirements?
The quality and repeatability of the output matter more than simply having the smallest number on the specification sheet.
4. What Do UltraPulse and SuperPulse Mean?
You may also see terms such as:
UltraPulse, SuperPulse, Short Pulse, or Fractional Pulse
on CO₂ laser product pages.
These terms generally describe particular pulse-output modes or manufacturer-defined operating modes.
However, buyers should not evaluate a machine based only on the name of a mode.
Ask for the actual specifications:
What is the pulse-width range?
What pulse energy is available?
Can pulse duration and energy be adjusted?
How repeatable is the output at the same setting?
Innymi słowy:
The mode name is useful, but the actual parameters and measured output are more important.
5. What Does mJ Mean?
The next important specification is:
mJ — millijoule
A millijoule is a unit of energy.
1,000 mJ = 1 joule (J)
Depending on the system, a CO₂ laser interface or specification sheet may show values such as:
10 mJ, 20 mJ, 30 mJ, or 50 mJ.
For a non-engineer, the simplest explanation is:
mJ tells you how much energy is delivered in a particular laser pulse or defined output event.
However, there is an important detail.
Before comparing the mJ specifications of two machines, confirm exactly what the manufacturer means by that value.
Depending on the machine, the displayed value may refer to pulse energy, microbeam energy, or another manufacturer-defined output parameter.
Therefore, you should not automatically conclude:
Machine A: 50 mJ = better
Machine B: 30 mJ = worse
without understanding how those numbers are defined and measured.
6. Does Higher mJ Mean the Laser Always Goes Deeper?
You will often hear:
“Higher energy means deeper penetration.”
There is some intuitive logic behind this, but it is too simple to use as a general rule for evaluating a CO₂ laser machine.
Under otherwise comparable conditions, increasing energy can increase the local tissue effect.
However, the actual ablation depth and surrounding thermal effect depend on several factors working together:
Pulse Width + Pulse Energy + Spot Size + Repetition + Tissue Properties
Dlatego:
mJ tells you how much energy is being delivered, but mJ alone does not tell you the exact treatment depth.
You should be especially cautious about claims such as:
10 mJ = X mm treatment depth
or:
30 mJ = Y mm treatment depth
without validated test conditions or supporting data.
Human tissue is not a fixed-thickness test material, and treatment response varies with multiple parameters.
7. What Is Spot Size?
The third major specification is:
Rozmiar plamki
Na przykład:
Focused Spot Size: 0.2 mm
This refers to the approximate diameter of the focused laser spot under defined optical conditions.
0.2 mm = 200 μm
That is a very small spot.
In fractional mode, the machine does not simply fire one spot.
A galvanometer scanner rapidly positions the laser beam to create many microspots across a treatment area.
Na przykład:
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
● ● ● ● ●
Together, these microspots create a:
Fractional Pattern
This is the basic concept behind a fractional CO₂ laser treatment pattern.
8. Why Does a Fractional CO₂ Laser Use Small Spots?
A simple way to understand spot size is to think about the tip of a pen.
A thick pen creates a wider mark.
A fine pen allows more precise marking.
The same basic idea applies to a focused laser beam.
A smaller focused spot concentrates the laser energy into a smaller area and allows the scanner to create fine microbeam treatment zones.
Fractional treatment also means the entire treatment area is not continuously ablated at once.
Instead, individual laser microzones are separated by untreated or less directly affected areas.
This is why you should consider:
Spot Size + Spot Spacing + Density
together.
The spot diameter alone does not describe the entire fractional treatment pattern.
9. Is a 0.2 mm CO₂ Laser Spot Good?
A specification such as:
Focused Spot Size: 0.2 mm
is useful information, but it does not automatically prove that the machine is high quality.
There is a major difference between:
a manufacturer claiming a 0.2 mm spot
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the machine consistently producing well-formed spots across the entire scan field.
For example, the spots in the center may look like this:
● ● ● ● ●
while the spots near the corners may become:
● ◉ ◍ ● ◉
If spot shape or size changes significantly across the scan field, the scanner, optics, alignment, or calibration may require further evaluation.
Therefore, don’t only ask:
“Is the spot size 0.2 mm?”
Also ask:
“Can you show me an actual full-area spot-pattern test?”
10. Is a Smaller Spot Always Better?
No.
This is another common marketing misconception.
For example, a machine advertised with a:
0.1 mm spot
may sound automatically superior to one with a:
0.2 mm spot.
But spot diameter is only one part of the optical performance.
You also need to consider:
Spot shape
Energy distribution
Optical alignment
Scanner accuracy
Output repeatability
A very small nominal spot with poor consistency is not necessarily better than a slightly larger spot that is clean, stable, and repeatable.
A useful rule for buyers is:
A good laser spot should not only be small. It should also be clean, consistent, and repeatable.
11. Why Must mJ and Spot Size Be Considered Together?
This is one of the most important concepts when understanding CO₂ laser specifications.
Imagine two circular laser spots:
0.2 mm diameter
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1.0 mm diameter
Now imagine both receive:
10 mJ
Are they equivalent?
No.
The same amount of energy is being distributed over very different areas.
This introduces another important term:
Fluence / Energy Density
Fluence is commonly expressed as:
J/cm²
The basic relationship is:
Fluence = Energy ÷ Area
In simple terms:
It is not enough to know how much energy is delivered. You also need to know how large an area that energy is distributed over.
This is why comparing mJ values alone can be misleading.
12. How Concentrated Is the Energy in a 0.2 mm Spot?
We can use a simple theoretical calculation.
Suppose the spot diameter is:
0.2 mm
The radius is:
0.1 mm = 0.01 cm
The area of a circular spot is approximately:
π × 0.01² = 0.000314 cm²
If pulse energy is:
5 mJ = 0.005 J
the theoretical average fluence is approximately:
0.005 ÷ 0.000314 ≈ 15.9 J/cm²
At:
10 mJ
it would be approximately:
31.8 J/cm²
At:
15 mJ
it would be approximately:
47.7 J/cm²
These are simplified theoretical calculations, not clinical treatment recommendations.
Real laser beams do not necessarily distribute energy uniformly across the nominal spot. Beam profile, effective spot-size definition, optical performance, and calibration can all affect the actual energy distribution.
The calculation is useful for understanding one important principle:
When energy is concentrated into a very small spot, even a relatively small mJ value can represent substantial energy density.
13. What About 30W or 40W?
Another common source of confusion is:
W — Watts
Na przykład:
30W CO₂ Laser
or:
40W CO₂ Laser
Watts measure:
Moc
while mJ measures:
Energia
They are related concepts, but they are not interchangeable.
A simple way to remember the major specifications is:
| Specyfikacja | Simple Meaning |
|---|---|
| W | Laser power |
| mJ | Energy delivered per defined pulse/output event |
| μs | How long the pulse lasts |
| mm | Size of the focused spot |
| J/cm² | Energy per unit area |
Therefore, when you see:
40W + 30 mJ + 200 μs + 0.2 mm
these are not four different ways of describing “laser strength.”
They describe different aspects of laser output.
14. How Should Pulse Width, mJ and Spot Size Be Read Together?
Now the three key specifications become much easier to understand.
Pulse Width — μs
Answers:
How long does the laser pulse last?
Pulse Energy — mJ
Answers:
How much energy is delivered in the pulse?
Spot Size — mm
Answers:
How large is the area into which that energy is focused?
So a specification such as:
200 μs + 20 mJ + 0.2 mm
should not be interpreted as three unrelated numbers.
Together, they describe important characteristics of the laser pulse.
The actual tissue effect also depends on factors such as:
Density, spacing, scan pattern, repetition, passes, and tissue characteristics.
15. Why Is Fractional Density Important?
Even if two machines have the same:
Szerokość pulsu
Pulse energy
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Rozmiar plamki
their treatment patterns can still be very different.
One reason is:
Density
In simple terms, density describes how many laser microspots are placed within a treatment area.
A lower-density pattern might look like:
● ● ●
A higher-density pattern might look like:
● ● ● ● ●
The second pattern places treatment points closer together.
Therefore, when evaluating a fractional CO₂ laser, don’t only examine an individual spot.
Also examine:
Spot Size + Spacing + Density + Scan Area
These parameters determine how the fractional pattern is distributed across the treatment area.
16. Why Does the Scanner Affect Spot Quality?
The laser source generates the CO₂ laser beam.
But in fractional mode, the system also requires a:
Galvanometer Scanner
to position the laser beam rapidly across the treatment area.
This means that even a good laser source cannot guarantee a good fractional pattern if the scanner or optical system is poorly adjusted.
Possible problems include:
Different spot sizes between the center and corners
Elongated or trailing spots
Uneven spacing
Missing spots
Distorted square patterns
Poor consistency near the edges of the scan field
This leads to another important buying principle:
A 0.2 mm spot-size specification is useful, but consistent spot quality across the full scan area is more meaningful.
17. How Can a Buyer Check Spot Quality?
You don’t necessarily need a laser laboratory to perform a basic visual comparison.
Ask the supplier to demonstrate a:
Spot Pattern Test
Use a relatively large square fractional pattern and inspect:
Center → Top → Bottom → Left → Right → Four Corners
Look for several things.
Are the spots approximately consistent in size?
Large differences deserve further investigation.
Are the spots regularly shaped?
Look for obvious elongation, tails, or merged points.
Is the spacing consistent?
Some areas should not appear significantly denser than others when the settings are unchanged.
Does the machine produce the same pattern repeatedly?
One good-looking test is not enough.
Repeatability matters.
18. Can a Paper Burn Test Measure CO₂ Laser Energy?
A paper burn test can be useful as a simple qualitative comparison.
When you keep the following conditions the same:
Energy + Pulse Width + Focus Distance + Spot Size + Test Material
you can visually compare:
Spot consistency
Pattern completeness
Missing points
Differences across the scan field
Repeatability between multiple shots
However:
A paper burn test cannot replace a calibrated laser power or energy meter.
For example, if the display says:
30 mJ
burning through several sheets of paper does not prove that the actual output is precisely 30 mJ.
Similarly:
Five sheets of paper cannot be converted directly into a specific treatment depth in human skin.
Paper thickness, composition, color, moisture, focus position, pulse duration, spot size, and other factors can all change the result.
Use paper testing for visual comparison and consistency checks, not as a calibrated measurement of clinical treatment depth.
19. What Should You Check on a CO₂ Laser Specification Sheet?
When comparing suppliers, start with these specifications:
| Parametr | What to Check |
|---|---|
| Laser Source | Type of CO₂ laser source |
| Power oceniany | For example, 30W or 40W |
| Szerokość impulsu | Available range and operating modes |
| Energia Pulsu | mJ range and how the value is defined |
| Focused Spot Size | For example, 0.2 mm |
| Density / Spacing | Whether fractional density and spacing can be adjusted |
| Obszar skanowania | Maximum treatment/scan area |
| Scan Patterns | Available fractional shapes |
| Skaner | Scanning performance and repeatability |
| Random Scan | Whether distributed/random scanning is available |
| Output Stability | Consistency during repeated operation |
But specifications are only the first step.
The next step should be:
Ask to see the actual machine operating.
20. Seven Questions to Ask a CO₂ Laser Supplier
You don’t need to be a laser engineer to evaluate a machine more carefully.
Ask these seven questions:
1. What CO₂ laser source does the machine use?
2. What is the pulse-width range?
3. What is the pulse-energy range, and what exactly does the displayed mJ value represent?
4. What is the focused spot size?
5. Can pulse energy and pulse width be adjusted?
6. Can you show me an actual full-area spot-pattern test?
7. Can you repeat the same test several times using exactly the same settings?
The last question is particularly useful.
Dlaczego?
Because:
The specification sheet tells you what the machine is designed to do. Repeated testing helps you see how consistently it actually does it.
21. μs, mJ and mm: The Simple Summary
If you remember nothing else from this article, remember this table:
| Parametr | Unit | Simple Explanation | What It Describes |
|---|---|---|---|
| Szerokość impulsu | μs / ms | How long the pulse lasts | Energy-delivery time |
| Energia Pulsu | mJ | How much energy is delivered | Energy per defined pulse/output |
| Rozmiar plamki | mm | How large the laser spot is | Area receiving the energy |
| Fluence | J/cm² | How concentrated the energy is | Energy per unit area |
| Moc | W | Laser power | System power level |
| Density | % / level / spacing | How closely spots are arranged | Fractional coverage pattern |
The key point is simple:
Never evaluate a CO₂ fractional laser using only one specification.
Conclusion: A Better CO₂ Laser Is Not Simply the One With Bigger Numbers
A CO₂ fractional laser advertised as:
40W
is not automatically better than a 30W machine.
A machine offering:
50 mJ
is not automatically better than one offering 30 mJ.
And a machine claiming:
0.1 mm spot size
is not automatically more precise than one specifying 0.2 mm.
What matters is how the complete system works together:
Pulse Width + Pulse Energy + Spot Size + Scanner + Optics + Output Stability
For buyers, the easiest way to remember this is:
μs tells you about time.
mJ tells you about energy.
mm tells you about spot size.
A spot-pattern test shows you the actual output pattern.
Repeated testing helps you evaluate consistency.
So the next time you compare two CO₂ fractional laser machines, don’t only ask:
“Which machine has higher power?”
A more useful question is:
“Can you show me the actual spot pattern several times using exactly the same settings?”
Because a well-designed CO₂ fractional laser is not simply capable of producing high output. It should also deliver the selected output consistently, precisely, and repeatably.
Related CO₂ Laser Guides
For a broader machine-quality comparison, continue with:
How to Evaluate a CO₂ Fractional Laser Machine: 4 Key Things to Check — RF Tube, Pulse Width, Spot Size & Skaner
Once you understand the specifications, move to the practical inspection guide:
5 Tests to Check a CO₂ Fractional Laser Machine Before Buying
