Ultrafast Laser Safety Calculator
Eye safety of femtosecond and picosecond lasers on the ICNIRP 2013 limits: sub-ns single-pulse limits, the average-power rule that governs MHz trains, eyewear OD and NOHD.
Educational only — not compliance-grade
These pages implement the published exposure limits for the cases each one states, but they are educational tools: no laser safety officer has signed them off.
- Do not use these results alone for PPE selection, NHZ / NOHD approval, controlled-area sign-off, enclosure/interlock approval, or formal classification.
- Always verify against ANSI Z136.1, IEC 60825-1, your local procedures, and the responsible laser safety officer / CLSO.
Average power
1.00 W
Peak power E/τ: 1.25e+5 W
Max energy per pulse
7.72 pJ
Retina, thermal, average power
Eyewear OD needed
3.21
At the output, 10.0 s. The single-pulse rule alone would call it safe
NOHD
396 m
Direct beam, diameter a + rφ
| Limit | 1. Single pulse | 2. Pulse groups (average) | 3. C_P × single pulse | Max per pulse | Your pulse / max |
|---|---|---|---|---|---|
| Retina, thermal | 38.5 nJ | 7.72 pJfull train: 8.00e+8 pulses | 38.6 pJC_P = 0.133, n = 2.00e+6 groups of 400 pulses in T_i | 7.72 pJ | 1620× (exceeds) |
| Anterior eye (skin limit, 2 × in the IR) | 611 nJ | 747 pJfull train: 8.00e+8 pulses | — | 747 pJ | 16.7× (exceeds) |
Energies per pulse in the beam (1/e² Gaussian, averaged over each limit's aperture). Rule 3 applies to the retinal thermal limit only; "—" means the rule doesn't apply (rule 2 needs two pulses).
A mode-locked oscillator puts tens of millions of pulses into the eye each second, so the average power, not the single pulse, sets the limit: ICNIRP 2013's rule 2 holds every group of pulses to the limit for the time it spans, up to the whole exposure. Pulses closer together than T_i (5 µs below 1050 nm, 13 µs above) also count as one pulse for the C_P rule. The single-pulse limits below 1 ns are ICNIRP 2013 Table 5's: 1 mJ/m² over the 7 mm pupil from 100 fs to 10 ps (× C_C above 1050 nm; no C_A), 2 C_A mJ/m² from 10 ps (20 C_C mJ/m² at 1050–1400 nm); shorter than 100 fs, and on the cornea below 1 ns, the irradiance is held at the shortest tabulated value. For the cornea (below 400 nm and above 1400 nm) ICNIRP 2013 (p. 287) also advises, as a conservative interim guideline, keeping sub-ns exposures below 10 % of the 1 ns limit; the page applies it. A beam under 1 mm (1/e diameter, d/√2 for the 1/e² d) is held to its peak on the cornea below 0.35 s (ICNIRP 2013 Table 5 note c).
Below 10 ps the retina is damaged by non-linear effects (laser-induced breakdown) rather than heat, which is why ICNIRP drops C_A there; it states that its limits also preclude non-linear injury. Eyewear for ultrafast lasers must keep its OD at the peak power: absorbing filters can saturate or bleach, so EN 207 tests mode-locked lasers separately ("M"). Use 0.25 s for an accidental glance at a visible beam and 10 s for the near infrared. Not modelled: pulse bursts, supercontinuum and harmonic lines (see the multiple-wavelength page), atmospheric attenuation, focusing optics.
Largest energy per pulse against the repetition rate at the output, for this pulse duration and exposure. Which rule binds depends on the train: for exposures longer than 0.25 s the C_P rule usually binds first as the rate rises, then the group (rule 2) rule at high rates.
Model and references
Textbook approximation. A standard approximation from the literature (for example paraxial, plane-wave or Gaussian-beam), valid within the range the page states. About the tiers
ICNIRP 2013 repetitive-pulse rules with the sub-ns rows (1 mJ/m² from 100 fs to 10 ps; the cornea below 10 % of its 1 ns limit, p. 287); round Gaussian beam over each aperture, NOHD with a + rφ. Not modelled: bursts, harmonics, eyewear saturation.
- ICNIRP (2013). Guidelines on limits of exposure to laser radiation of wavelengths between 180 nm and 1,000 µm. Health Phys. 105(3), 271–295. Repetitive pulse exposures (p. 287), Tables 4, 5 and 8. doi:10.1097/HP.0b013e3182983fd4