小型高灵敏度水下拉曼光谱系统

为了使水下拉曼光谱系统更加易于搭载和布放,并进一步提高其探测能力,研制了一套探头式的小型高灵敏度水下拉曼光谱系统并对其探测能力进行了评估。通过优化结构设计和严格的器件选型,系统的体积和重量得到了有效的控制,其主体舱尺寸为Φ260mm×L795mm,重量为548N,仅为国际上报道的首台深海拉曼光谱系统(DORISS)质量的三分之一。将激光器从主体舱移至探头舱,有效避免了传统光学探头中激发光耦合进入光纤时产生的耦合损失以及激光在传输过程中引起的杂散光干扰。系统采用了300mW能量可调激光器配合高衍射效率的体相位全息光栅和半导体制冷CCD,有效提高了探测灵敏度。实验结果表明,系统对于硫酸根的检测限在0.4mmol·L-1以下,是DORISS探测能力的4倍,同时能够实现对水下矿石种类的原位鉴定。该深海拉曼光谱系统在海洋原位探测方面展现出了良好的应用前景。

A compact underwater Raman spectroscopy system with high sensitivity

In order to reduce the volume and weight of the underwater Raman system, and to improve its portability and detection sensitivity, a compact underwater Raman spectroscopy system with high sensitivity was developed and assessed. Through elaborate selection of components, a compact structural design was realized with both the weight and the volume well controlled. The size of the main body was kept at 795 mm in length and 260 mm in diameter, with a weight of 548 N, one third of the weight of reported DORISS (the first deep ocean Raman in-situ spectroscopy system). The laser was housed in the optical probe rather than in the main body, hence higher excitation efficiency was achieved with high power density. There are two advantages to put the laser head in the probe. A desirable excitation power density could be obtained without the consumption of laser beam during transmission in fiber, and better signal to noise ratio could be achieved without the stray light raised by the interaction of laser and optical fiber. In addition, 300 mW powered laser, efficient volume phase holographic grating and TEC cooled CCD detector were used to improve the system performance. The experimental results show that the LOD (limit of detection) of SO₄^2- was less than 0.4 mmol·L^-1. It's about four times than the value achieved by DORISS. Meanwhile the system can be used to identify minerals. All above prove the system to be highly potential in ocean exploration.