Reading a Laser Datasheet: Which Values Are Guaranteed
*A specification table looks like a list of facts. In practice it mixes guaranteed minima, typical figures and
test conditions, and treating all three the same is how a design ends up not meeting its requirement. This
article explains how to read each kind of value in the ERDI datasheets — and, where a value varies across the
range, why.*
In short: a value preceded by ≥ or ≤ is a limit the part is accepted against. A value with no symbol is
either a nominal operating point or a property of the design. Environmental figures are demonstrated by test,
not by inspection of every unit. Ask which one you are reading before you design to it.
Why the distinction matters
A datasheet has to serve several readers at once: the engineer checking whether a part will work, the purchasing
team comparing options, and the quality function defining what will be accepted. The table is compressed to do
all three jobs.
That compression hides information. Three different kinds of statement appear in the same column:
A guaranteed limit — every unit is accepted against it. If the datasheet says pulse energy is ≥800 µJ, a
unit that delivers 750 µJ does not ship.
A nominal value — what a typical unit does, useful for design but not a commitment per unit.
A design property — a quantity that follows from the construction, such as the wavelength or the beam
quality. It is not measured on every unit because it cannot meaningfully vary.
Designing to a nominal as though it were a limit is the common error. The part will work on the bench and fail
at the acceptance test.
The symbols, and what they mean here
Every model in this range publishes its specification in the same form. The symbols are consistent and worth
knowing:
| Symbol | Meaning | How to treat it |
|---|---|---|
| ≥ | At least this value | A guaranteed minimum. Design to it, not above it |
| ≤ | At most this value | A guaranteed maximum. This is a limit to respect |
| No symbol | Nominal or design property | Confirm against the test report before relying on it |
| Ranges (1–10 Hz) | Adjustable range | The nominal operating point within it may differ |
Applied to the ER800 as an example:
Wavelength 1535 nm design property Pulse Energy ≥800 µJ guaranteed minimum Pulse Width 7 ns design property of the cavity Pulse repetition rate 1–10 Hz adjustable range Drive pulse width ≤ 3 ms guaranteed maximum — do not exceed Operating temperature −40 to +65 °C demonstrated by test
The generated 3D model on each product page can be used to check the mechanical envelope before ordering, and
the datasheet carries the same table in printable form.
The environmental figures
Environmental specifications are a different kind of claim from the optical ones, and it is worth being clear
about how they are established.
Operating temperature — the range over which the published optical performance is maintained. Most models in
this range are specified −40 °C to +65 °C. The high-repetition family (ER10–ER70) is specified −45 °C to +65 °C.
Storage temperature — the range over which the unit may be stored without damage. This is wider than the
operating range, because no optical performance is required while the unit is not running.
Storage range varies across the range, and the variation is real rather than an inconsistency:
| Group | Models | Storage temperature |
|---|---|---|
| High-repetition family | ER10, ER20, ER40, ER70 | −55 °C to +85 °C |
| MINI-100 | MINI-100 | −55 °C to +85 °C |
| Other models | ER100 through ER10000 | −55 °C to +75 °C |
If a requirement calls for storage at +80 °C, that is a question to raise at the specification stage for the
model concerned, rather than something to assume from another model in the range.
Shock — 1500 G for 0.5 ms.
Vibration — 20–2000 Hz at 20 G.
These are demonstrated by test rather than by inspecting each unit. The MINI-100 is additionally stated as
meeting MIL-STD-810G test standards; the other models publish the vibration and shock figures without that
reference, so a programme requiring formal MIL-STD qualification should raise it as a requirement rather than
infer it from a neighbouring model.
Values that are design properties
Some entries in the table cannot meaningfully vary between units, and knowing which ones those are saves
unnecessary concern.
Wavelength. Set by the erbium energy levels in the glass host. Every model in the range is 1535 nm. It is not
tuned per unit and does not drift with drive conditions in any way that matters for a receiver designed for the
band.
Beam quality. TEM00 for the whole range. It follows from the cavity design.
Pulse width. Set by the microchip cavity — the length of the gain medium, the saturable absorber and the
coatings. It is a property of the model, not of the driver. This is why
lengthening the drive pulse does not lengthen the optical pulse.
Polarisation and similar optical properties, where stated, fall into the same category.
These are the entries where comparing two models on the number is meaningful, but where the number is unlikely
to vary between units of the same model.
Values that are nominal, and how to confirm them
Two entries in particular are worth confirming rather than assuming.
Pulse stability — published as 5% or 10% depending on the model. This describes the unit-to-unit and
pulse-to-pulse variation of the energy, and it matters directly to a receiver with a fixed threshold. If the
detection logic is sensitive to amplitude, this is a figure to characterise on the actual unit rather than
design against the datasheet alone.
Beam divergence and raw beam diameter — published so the host optics can be designed. They are nominal
figures, and the divergence is stated as a full angle unless noted otherwise. The
terminology list on the site defines each of these terms as the datasheets use
them.
For anything where the margin is thin, the answer is the same: confirm against the factory test report supplied
with the unit.
Where the numbers affect the design
A short guide to which value to look at for which decision.
| The decision | The value that decides it |
|---|---|
| Long range against a diffuse target | Pulse energy (guaranteed minimum) |
| Separating two close returns | Pulse width |
| Update rate, or scan point density | Repetition rate |
| Fitting the envelope | Dimensions and weight |
| What the driver must supply | Drive pulse width (maximum), voltage, current |
| Whether the package survives the environment | Operating temperature, shock, vibration |
| Receiver design | Raw beam diameter, beam divergence |
| Detection threshold margin | Pulse stability |
If the decision is the last one, note that stability is the figure most likely to need measuring on the actual
unit.
Questions worth asking of any datasheet
Not only these — of any supplier's.
Is this value a minimum, a maximum, or a typical? If the symbol is missing, ask.
At what drive and temperature condition? A pulse energy figure without a stated condition is not comparable
to another.
How was it established — design, test, or calculation? Environmental claims in particular.
What is the test report, and is one supplied with the unit? A factory test report per unit is worth more
than any datasheet, because it describes the part in your hand.
Which values are family-wide rather than per-model? Where models share a mechanical and environmental table,
that is stated on the datasheet itself. The optical parameters are always per model.
How this range is documented
Every model publishes:
- a specification datasheet with the optical, mechanical and environmental tables
- a 3D model in glTF binary, for mechanical integration in CAD
- an outline drawing showing the envelope and mounting features
All of them are linked directly from the Engineering Center, which carries the
full document index. Dimensioned drawings and the controlled STEP source are released on request so that the
correct revision is issued against a specific project.
Related reading
- Pulse width and range resolution — why pulse width is fixed
- Integrating a microchip laser source — the drive limits in
practice
— using the minimum-energy figure in a link budget
Next steps
If a requirement depends on a figure whose status is unclear, Contact / RFQ is the
right route — include the model, the requirement and the value in question, and we will confirm whether it is
guaranteed, typical, or demonstrated by test. The full specification tables are on the
Laser Sources page.