532nm laser is used for underwater communication. Because the low loss window in seawater is 0.46nm~0.54nm, and the pulse peak energy should be greater than 200mJ, the pulse width is generally 10ns~20ns, the repetition frequency is about 50Hz, and the divergence angle is the smaller the better, generally less than 0.1mrad, the laser spot is as uniform as possible, and the 532nm Nd:YAG laser with electro-optic Q-switching can be applied to these aspects.
In order to get high peak power, it is necessary to concentrate the energy into one pulse by Q-switching technology. LiNbO3 has a large electro-optic coefficient, large acousto-optic coefficient and good nonlinear performance. It is widely used in photoregulators and waveguide material substrates as well as Q-switches for Nd lasers. Insoluble in water, not easy to deliquesce, does not require sealed storage, low transmission loss, stable chemical and mechanical properties.
The frequency doubling crystal is a LBO crystal. The LBO crystal is a negative biaxial crystal. The destruction threshold is 4 times that of KTP. The effective nonlinear coefficient is one-third of the KTP crystal, and has a wide allowable angle and a small deviation angle. With Class I phase matching, the two pass surfaces of LBO are plated with a two-color antireflection coating for 1064 nm and 532 nm.
Mirror——M1 – 1064nm total reflection film is plated on the side near electro-optic crystal. M2 – 1064nm output mirror. M3 – 45 ° reflector.
Using a frequency-doubled Q-switched mode-locked Nd:YAG laser, 35 532 nm pulses are generated per second. In general waters, the experimental results in three-dimensional directions are higher than 6 135 mm; in deep water pools, the distance resolution is experimentally obtained，it is 91144m, the lateral resolution is about 6135mm, and the distance resolution is limited by the 9ns pulse width of the Q-switched laser.
532nm Single Frequency Pulsed Laser for Underwater Communication
|Model||Energy (mJ)||Energy Stability||Pulse Width(ns)||Repeat Frequency(Hz)|
- Single-mode output, good beam quality
- Light pump output, high cost performance
- Reliable structure, permanent fixing technology
- Highly integrated system, easy to operate
- It is widely used in satellite laser ranging
- Doppler wind measurement
- underwater imaging
- laser fine drilling
- laser shock strengthening
- nonlinear frequency conversion and other fields