Fluence, Coatings and Lifetime: Why 10 mJ Is Not 100 × 100 µJ
The catalogue quotes energy per shot. The coating sees energy per square centimetre, and that's what decides how long the part lasts.
Ten millijoules spread over a square centimetre is 10 mJ/cm². Focus it into a square millimetre and it's 1 J/cm², a hundred times hotter on the same optic. Nothing changed in the source; the optics after it did.
Why the bigger models use a wider beam
The millijoule units emit from roughly 0.8 mm, the compact ones from about 0.3 mm. Part of the extra energy gets spent by the larger area, which is one reason the numbers aren't as far apart in practice as they look on paper.
Life, in hours
| Model | Energy | Life | At rated rate |
|---|---|---|---|
| MINI-100 / ER100 | 100 µJ | 10 M shots | ≈ 280 h at 10 Hz |
| ER200–ER900 | 200–900 µJ | 1 M shots | ≈ 55 h at 5 Hz |
| ER2000 | 2 mJ | 10 M shots | ≈ 555 h at 5 Hz |
| ER4000–ER10000 | 4–10 mJ | 1 M shots | ≈ 55 h at 5 Hz |
The non-monotonic bit is worth noticing. The ER2000 carries the same ten-million figure as the microchip, while the larger units drop to one million. That reflects how hard each design is driven, not how much energy it makes.
What kills a coating
Over-driving first. Then dust, then a beam clipping an aperture, then thermal cycling. A fingerprint on a coating is worse than no coating at all.
Longer pulses for bigger energies
Pulse width runs 3.5 ns on the microchip, 5–7 ns in the compact range, 12–13 ns from 2 mJ up. Same energy over a longer pulse is lower peak power on the surface. That's part of how the bigger units survive their own output.
Burn-in
Run at rated duty for a set number of shots, measure energy at both ends, record the baseplate. A unit that drifts during burn-in won't settle down in the field.
Cap the optics when the unit is idle, clean them the way the coater specifies, and count shots in the host rather than on the calendar.
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