Every LiDAR architect reaches the same fork: 905 nm or 1550 nm. The pitch on 1550 nm — "eye-safe" — is real, but it is also misread. Neither wavelength is faster or more accurate. The difference is how much power the eye-safety rules let you run, and what that power costs to generate and detect. That is the whole decision.
The one fact that drives the choice
At 905 nm, the eye's lens focuses the beam onto the retina, so the maximum permissible exposure (MPE, per IEC 60825-1) is tight. At 1550 nm, the cornea and aqueous humour absorb the light in front of the retina, so the permitted exposure is roughly a thousand times higher. A 1550 nm system can therefore run far more average power for the same safety class. The cost of that headroom is an InGaAs receiver and a more expensive laser — and that is the trade.
1. Eye safety: the headline, stated honestly
"Eye-safe" is a classification result, not a wavelength property. 1550 nm is easier to keep in a high safety class because the MPE is so much higher. 905 nm is perfectly safe when the design respects its tighter MPE — which is why every consumer robot vacuum and handheld rangefinder on the planet ships 905 nm. The question is not "which is safe" but "which gets me the power I need within the class my product must meet".
2. Cost: 905 nm is a silicon problem, 1550 nm is not
A 905 nm receiver is a silicon avalanche or PIN photodiode — the most mature, highest-volume optoelectronic part there is. Cheap, sensitive, available from many suppliers. A 1550 nm receiver is InGaAs: lower quantum efficiency, higher noise, several times the price, and a smaller supplier base. The laser is the same story in reverse — 905 nm edge emitters are commodity parts; 1550 nm sources (erbium-glass, fibre, OPO) cost more per watt. For consumer, robotics and industrial volumes where the BOM decides the design, this gap is decisive.
3. Range: set by the safety budget, not the wavelength
Range follows from permitted average power and receiver aperture. Because 1550 nm is allowed more power for the same class, it can reach longer range at equal safety — which is why long-range automotive programs favour it. But high-peak-power 905 nm with a sensitive silicon APD also reaches long range; automotive 905 nm LiDAR ships today. The honest statement: 1550 nm gives more eye-safe power headroom, 905 nm gives the same range at lower cost if your class allows it.
4. The details that actually matter in the spec
- Wavelength stability — 905 nm drifts around 0.25 nm/°C on a bare part; 1550 nm (erbium-glass) drifts less, which matters for narrow receiver filters in long-range scanning.
- Atmospheric scatter — 905 nm scatters a little more in fog and dust; 1550 nm penetrates slightly better. Real, but a second-order effect next to the safety and cost gap.
- Detector noise — silicon APDs at 905 nm are lower-noise and higher-QE than InGaAs at 1550 nm, which partly offsets the power advantage.
Which one, by application
| Application | Dominant choice | Why |
|---|---|---|
| Robot vacuum / handheld rangefinder | 905 nm | BOM-critical, short range, silicon receiver |
| Industrial automation / AGV | 905 nm | Cost, supply maturity, adequate range |
| Automotive LiDAR (long range) | 1550 nm (or high-power 905) | Eye-safe power headroom for long range |
| Airborne / surveying mapping | 905 nm low-drift, or 1550 | Range and wavelength-stability needs |
LumeLiDAR makes both: the 905 nm pulsed family and the 1550 nm eye-safe and 1535 nm erbium-glass sources. The choice is yours; the parts are ours either way.
The 905 nm emitter family you would use
If the decision lands on 905 nm, the emitter selection is its own problem — peak power, package, beam and temperature drift. Our 905 nm selection guide walks that through, and the dedicated second-source pages cover the parts designers most often replace: the discontinued ams OSRAM SPL PL90_3 and the single-sourced ROHM RLD90QZW3.
Frequently asked
Is 1550 nm actually safer than 905 nm?
For the same safety class, yes — but the reason is physical, not marketing. The cornea and aqueous humour absorb wavelengths from about 1400 nm upward, so a 1550 nm beam is stopped in front of the retina and the maximum permissible exposure is roughly a thousand times higher than at 905 nm, where the lens focuses the light onto the retina. That lets a 1550 nm system run far more average power for the same eye-safety classification. The trade is cost: 1550 nm needs InGaAs detectors and erbium-glass or fibre lasers, both more expensive per watt than the silicon ecosystem at 905 nm.
Which reaches longer range?
Range is set by your safety budget, not by the wavelength directly. Because 1550 nm is allowed more average power for the same class, a 1550 nm system can push longer range at equal safety. But high-peak-power 905 nm with a sensitive silicon APD also reaches long range, and automotive 905 nm LiDAR exists. The honest statement is: 1550 nm gives you more eye-safe power headroom; 905 nm gives you the same range at lower cost if your safety class allows it.
Why is 905 nm cheaper?
Because the whole receive and transmit chain is silicon. A 905 nm system uses a silicon avalanche or PIN photodiode — mature, high-volume, cheap. A 1550 nm system needs InGaAs detectors, which are lower quantum efficiency, noisier and several times the price, plus a more expensive laser source. For consumer, robotics and industrial volumes where BOM dominates, that gap decides the design.
Related reading
How to choose a 905 nm pulsed laser diode
Five decisions — power, package, beam, drive and temperature drift — that pick the right emitter for LiDAR, rangefinders and sensors.
How to design a pulsed laser diode driver
Current source, not voltage source: low-inductance loops, reverse-voltage clamping, thermal derating and the GaN-vs-Si MOSFET choice.
VCSEL vs EEL for ToF: which emitter to choose
Where each emitter wins on beam shape, wafer-level test and peak power for time-of-flight systems.
Tell us the range and safety class.
Whether you land on 905 nm or 1550 nm, we can quote the emitter and the matching receiver and driver as one optical front-end.