As the application of laser ranging technology in areas such as unmanned aircraft, border surveillance, and autonomous systems becomes increasingly widespread, system integrators are facing a serious challenge: how to achieve longer-distance measurement while ensuring eye safety. Among various long-distance solutions, erbium glass lasers with a working wavelength of 1535nm have become the preferred choice for more system integrators due to their unique advantages.
This article will explain in detail why erbium glass lasers can achieve safe long-distance measurement for the human eye.
About Erbium Glass Lasers
Erbium glass lasers are a type of solid-state laser that uses glass materials doped with erbium ions as the gain medium. In the communication wavelength range (such as 1.54 μm), erbium ions can efficiently achieve energy conversion and are widely used for laser amplification and signal enhancement. They mainly rely on the excitation of erbium ions by a pump source to convert low-energy photons into high-energy lasers, and achieve signal amplification through stimulated emission. Their output wavelength is highly matched to the mainstream transmission window of optical fiber communication, thus being able to play a significant role in signal enhancement for long-distance optical signal transmission. Additionally, the 1535 nm wavelength is within the safe range for the human eye, with strong atmospheric absorption. The cornea and lens have a significantly increased absorption rate for this wavelength band, greatly reducing the risk of laser damage to the retina. This enables erbium glass lasers to maintain high output power while still meeting Class 1M or Class I eye safety standards, suitable for long-term monitoring in urban environments or areas with people. Their narrow linewidth and high coherence characteristics also enhance their anti-interference ability, and combined with coherent detection technology, can further improve the signal-to-noise ratio and detection distance.
Advantages of Erbium Glass Lasers in Long-Distance Transmission
Wavelength advantage, low loss: The output wavelength of erbium glass lasers is concentrated in the 1530-1560 nm band. This frequency band is the "golden window" for long-distance transmission, with low fiber optic transmission loss and high penetration.
Efficient energy utilization: During long-distance laser transmission, the output power and stability tend to decrease as the distance increases. For this, erbium glass lasers usually contain ytterbium ions, and ytterbium ions can efficiently absorb the pump energy and transfer it to erbium ions, thereby significantly increasing the laser output power and achieving efficient utilization.
Directional emission, stable beam quality: In long-distance laser transmission, there are many factors that can cause loss, among which beam divergence is one. The laser beam expands in diameter with the transmission distance, resulting in energy dispersion. Erbium glass lasers can achieve base transverse mode (TEM₀₀) output through the mode selection of the resonant cavity, ensuring stable beam quality.
Integration advantages, higher cost-effective amplification ranging: Signal attenuation is the core bottleneck in long-distance transmission. Erbium glass, with its wavelength consistent with erbium-doped fiber amplifiers (EDFA), can directly amplify attenuated signals, enabling ultra-long-distance transmission and having higher cost-effectiveness.
Summary
The erbium glass laser, with its unique performance, has significant advantages in long-distance laser signal transmission. It can achieve long-distance ranging functions while ensuring eye safety, and is widely applicable to those scenarios that have strict requirements for performance, safety, and system integration.
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