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Q-switched fiber lasers initiative is expected to improve the accuracy of laser radar
- Sep 29, 2016 -

Q-switched fiber lasers initiative is expected to improve the accuracy of laser radar

Detection accuracy can be described as the lifeblood of a laser radar (LIDAR) system where high precision LIDAR technology has been unswerving pursuit. For Doppler Coherent Laser lidar, an effective way to improve the detection accuracy is to achieve its long pulse output transmission source.

In using the injection-locked laser radar technology emission source, the pulse width is controlled mainly by the laser (slave laser). Pulse fiber ring laser has a one-way operation, long pulse output characteristics, and therefore can be used as an ideal from a laser used in the injection-locked laser.

Currently, reports on the 2 μm band pulse fiber ring laser use more passive Q mode. Passively Q-switched laser has the advantages of simple structure, but its pulse repetition rate and pulse width are often uncontrollable, which causes it unsuitable for use in injection-locked technology.

To avoid passively Q technology these shortcomings, Professor Ju Youlun group School of Astronautics, Harbin Institute of Technology uses active Q mode, use the free space acousto-optic modulator to achieve a stable thulium-doped fiber ring laser at 2 μm band. Related research has been published in Chinese Optics Letters 9th, 2016 (W. Liu, et al., Actively Q-switched ring Tm-doped fiber laser with free space structure).

Compared with passive Q-technology, active in the Q-switched laser repetition rate, pulse width laser performance can get better stability control. The acousto-optic modulator is to achieve active Q usual choices, which are mainly fiber-coupled and free-space type two types. Taking into account the free space acousto-optic modulator 2 μm band has a higher damage threshold, more conducive to high-energy pulse output, the group using its built thulium-doped fiber ring laser.

At 100 Hz repetition rate, when the cavity length is 6.68 m, the laser system to obtain a single pulse energy 150 μJ, pulse width 207 ns pulsed laser output; in the laser cavity length by conduction fiber increased to 12 m after, in the same pulse energy, the output pulse width reached 382 ns.

Professor Ju Youlun said preliminary results of the study in the 2 μm band solves the injection-locked laser output from the laser pulse width narrower issues. The next phase of work will thulium-doped fiber ring laser further optimization of the parameters, it is expected to be applied to the final Coherent Doppler lidar system.