Erbium glass laser, with a safe working wavelength of 1.53 μm for human eyes, compact shape, high single pulse energy, and stable beam quality, has become the core light source of current laser ranging systems. This wavelength is located in the atmospheric transmission window, with a low water absorption peak and attenuation better than 1 μm band in cloudy and foggy environments. At the same time, it meets international human eye safety standards and can work for long periods of time in open spaces without additional protection.

A typical device uses erbium ytterbium co doped phosphate glass as the gain medium, and side or end pumped 940 nm semiconductor laser. Erbium ions absorb 940 nm and undergo Yb → Er energy transfer, achieving a 1.53 μm four level transition. As shown in Figure 1.

(Figure 1)

Due to the long lifetime of the upper energy level of up to 8 ms, the system can adopt a low repetition rate Q-switching method to obtain single pulse energy at the micro focus or millifocus level in nanoseconds, with peak power in megawatts, effectively improving the ranging signal-to-noise ratio.

The ranging chain consists of a laser, transmitting optics, receiving telescope, avalanche photodiode, and time measurement unit. As shown in Figure 2.

(Figure 2)

After the system emits a single pulse, record the echo flight time Δ t and the distance R=c ·Δ t/2. The 1.53 μ m wavelength corresponds to extremely low response of silicon detectors, so InGaAs avalanche tubes are used in conjunction with narrowband filters to suppress background light. Due to the high pulse energy, ranging from several kilometers to tens of kilometers can be completed at a repetition rate of 0.1-1 Hz, without the need for high-frequency accumulation, achieving single pulse detection and simplifying signal processing.

In terms of beam shaping, the laser rod has a beam diameter of 2-4 mm, which is expanded 5-10 times by the Galileo telescope. The far-field divergence angle is compressed to 0.2~0.5 mrad, ensuring the energy density of the light spot and reducing the influence of atmospheric scintillation. The receiving end uses an 80-150mm aperture Cassegrain telescope to collect echoes and focus them onto the InGaAs APD system.

The erbium glass laser independently developed, produced, and sold by RealLight is known for its high reliability and cost-effectiveness. Please feel free to inquire.

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