1535nm Laser Technology
What is a 1535 nm Laser?
A 1535 nm laser is a pulsed solid-state laser that emits in the 1.5 µm eye-safe band. The wavelength sits at the boundary of the retinal hazard region: 1535 nm light is strongly absorbed by the cornea and the lens before it can reach the retina, so the permissible exposure limit is orders of magnitude higher than at 905 nm. That is why 1535 nm sources can be operated at higher pulse energy in open environments — the property that makes long-range, eye-safe ranging and LiDAR practical.
ERDI builds 1535 nm sources on Er:Yb glass (erbium–ytterbium co-doped phosphate glass), pumped by a 940–980 nm laser diode, in a microchip resonator that is Q-switched to produce 3.5–13 ns pulses from 10 µJ to 10 mJ.
- 1535 nm laser — the emission wavelength of the Er:Yb glass gain medium
- Eye-safe laser — the 1.5 µm band, where corneal absorption protects the retina
- 1.5 µm laser — the same band, referenced by wavelength rather than by nanometres
Why choose 1535 nm over 905 nm?
Most short-range LiDAR and rangefinder designs start at 905 nm because silicon detectors are cheap and sensitive there. The trade appears as soon as the system has to reach further, or operate where people are present.
| Parameter | 1535 nm | 905 nm |
|---|---|---|
| Eye safety | Excellent — energy is absorbed by the cornea before reaching the retina; much higher permissible exposure at the same pulse energy | Limited — energy focuses onto the retina; permissible exposure is far lower |
| Atmospheric loss | Low — outside the strong water-vapour absorption lines, good transmission in haze and light fog | Higher — more scattering in haze, fog and precipitation |
| Range capability | Longer — higher usable pulse energy at the same eye-safety class | Medium — energy is capped by eye-safety limits |
| System size | Compact — microchip source from 14.5 × 6.3 × 4.37 mm / 2.5 g | Compact — comparable emitter size |
| Detector | InGaAs (or upconversion / SiGe APD) | Silicon APD |
| Typical use | Long-range ranging, UAV LiDAR, mobile mapping, remote sensing | Short-range LiDAR, proximity sensing, consumer ToF |
Neither wavelength is universally better. 905 nm wins on detector cost and availability; 1535 nm wins wherever range, atmospheric margin or eye safety in populated areas decide the specification.
ERDI technology: 1535 nm Er:Yb glass microchip lasers
Our sources are built as a single passive assembly rather than a free-space bench, which is what makes the 2.5 g packages possible.
| Element | What it does |
|---|---|
| Er:Yb glass | Erbium–ytterbium co-doped phosphate glass. Ytterbium absorbs the 940–980 nm pump band efficiently and transfers the energy to erbium, which lases at 1535 nm. The glass host allows very high doping in a few millimetres of material. |
| Microchip structure | Gain medium, saturable absorber and cavity mirrors are bonded into one monolithic chip. No alignment, no adjustable optics, and the cavity length is set by the chip thickness — which fixes the pulse width in the few-nanosecond range. |
| LD pumping | A 940–980 nm laser diode pumps the chip through its face. Drive conditions stay simple and low-voltage: 2 V for the compact range, ≤ 14 V for the multi-mJ models, with drive pulse widths from ≤ 1.1 ms. |
| Q-switched operation | Passive Q-switching by the bonded saturable absorber produces short, high-peak-power pulses without an external driver or high-voltage switching stage — energy from 10 µJ to 10 mJ in 3.5–13 ns. |
The result is a source with no warm-up, no alignment drift, TEM00 output, 0.3–0.8 mm raw beam diameter and stable operation from −40 °C to +65 °C — specified for integration rather than for a laboratory bench.
Where 1535 nm sources are used
- Laser ranging — handheld, vehicle and gimbal rangefinders from 100 µJ to 10 mJ
- UAV LiDAR — SWaP-critical transmitters from 2.5 g
- Mobile mapping — 800 µJ to 2 mJ at 1–10 Hz for corridor-scale coverage
- Remote sensing and research — up to 10 mJ for extended link budget and experimental transmitters
See Applications for the parameter sets these systems need, and OEM Solutions for integration and customisation.
Frequently asked
Is 1535 nm really eye-safe?
It is eye-safe in the sense that the eye-safety limit is far higher than at visible or 905 nm wavelengths: the cornea absorbs 1.5 µm radiation before it reaches the retina. It is not "safe at any power" — the source still has to be classified and the system still has to be evaluated against the applicable laser safety standard.
What pulse energy do I need?
Enough to close your link budget, with margin. A practical starting point: 10–100 µJ for short-range handheld and dense industrial sensing, 200–500 µJ for multi-kilometre ranging and long-range LiDAR, 0.8–2 mJ for mobile mapping and extended observation, 4–10 mJ for remote sensing and ultra-long-range channels.
Why is the pulse width fixed?
Because it is set by the microchip cavity, not by an external driver. The short pulse concentrates the energy in time, which raises peak power and improves the signal the receiver sees for a given pulse energy.