通过相干合束提高光纤激光源的输出功率是目前研究的一个热门领域,其中多束激光的相位控制是提高合束效率的关键技术之一.本文基于主动相位锁定技术对传统外差探测法进行了改进,基于压电陶瓷及光纤电光相位调制器双通道伺服反馈,实现了对同一激光源输出的两路相位独立变化的1531 nm激光长时间的相位锁定.通过选择合适的PID控制参数,将反馈带宽拓展到了220 k Hz(受限于PID控制器自身带宽).最终的相位锁定控制在0.88?以内,即相位控制精度为λ/400,经过160 s平均后可得到相位锁定的最佳值为0.006?,整体实验装置结构简单、运行稳定.
Determination of the chemical composition of cement and ratio values of clinker plays an important role in cement plants as part of the optimal process control and product quality evaluation. In the present paper, a laboratory laser-induced breakdown spectroscopy （LIBS） apparatus mainly comprising a sealed optical module and an analysis chamber has been designed for possible application in cement plants for on-site quality analysis of cement. Emphasis is placed on the structure and operation of the LIBS apparatus, the sealed optical path, the temperature controlled spectrometer, the sample holder, the proper calibration model established for minimizing the matrix effects, and a correction method proposed for overcoming the ＇drift＇ obstacle. Good agreement has been found between the laboratory measurement results from the LIBS method and those from the traditional method. The absolute measurement errors presented here for oxides analysis are within 0.5%, while those of ratio values are in the range of 0.02 to 0.05. According to the obtained results, this laboratory LIBS apparatus is capable of performing reliable and accurate, composition and proximate analysis of cement and is suitable for application in cement plants.
