光束发射参数对蓝绿激光海洋传输特性的影响

蓝绿激光位于海水低损耗窗口区,由于水体吸收和散射,光束在水下传输将发生时空扩展和波形畸变。基于蒙特卡罗仿真分析了蓝绿激光海洋传输特性,特别是激光发射参数对接收光场分布的影响。提出通过调节发射端的光束发射参数,对发射光束进行预聚焦,可在一定程度上抵消水体传输引起的光束扩散影响。分析和仿真结果表明,IB水体中,当预聚焦角度与水体小角度散射特征值相当时,可在设计汇聚距离前形成一段光束扩散缓慢的平坦传输区域;当预聚焦角度大于小角度散射特征值的2倍时,可在设计聚焦距离附近形成汇聚效果;预聚焦角度越大,汇聚效果越明显;水体变差时,相应有效汇聚距离变短。研究成果为调控蓝绿激光信号在海水的传输特性提供了一种新的思路。

Influence of Beam Parameters on Propagation of Blue Green Laser Underwater

The blue-green spectrum in the range of 450$sim$550 nm is the only low loss optical window of seawater.Due to the absorption and scattering of water, the underwater propagation of the laser beam willhave time-space expansion and waveform distortion. Based on Monte Carlo simulation, the propagationcharacteristics of blue-green laser in seawater have been analyzed, especially the influence of laseremission parameters on the distribution of receiving light field. By adjusting the beam parametersof the transmitter and focusing the laser beam in advance, the influence of beam diffusion causedby underwater transmission can be eliminated to some extent. The analysis and simulation resultsshow that when the pre-focusing angle is equal to the small angle scattering eigenvalue of water,a flat transmission area with slow spread of laser beam can be formed in Jerlov type IB water beforethe designed focus distance. When the pre-focusing angle is greater than twicethe scattering angleof water, the convergence effect can be formed near the designed focus distance, and the focus effectis proportional to the pre-focusing angle. When the water quality becomes worse, the correspondingeffective focus distance becomes shorter. The research results provide a new way to improve thetransmission characteristics of blue-green laser signal in seawater.