| The laser weapon in the mid-wave infrared band is one of the important means to counter the medium-wave infrared precision guided weapon.At present,the laser transmission device adopted by such weapons has the defects of large volume,complicated structure,poor flexibility,low transmission efficiency,and difficult maintenance,which affects the laser transmission effect and seriously restricts the performance of the laser weapon.The use of optical fibers for high-power laser transmission has the advantages of flexible transmission,high theoretical transmission efficiency,small size,light weight and good environmental adaptability.It can overcome the inherent shortcomings of traditional laser transmission device,which plays an important role in improving the performance of laser weapon.At the same time,the infrared energy transmission fiber has made continuous progress in materials and processes,and laid the foundation for its application in high-power laser transmission.However,most of the current research on high-power laser and fiber coupling are concentrated in the near-infrared band,and mainly for quartz fiber.In order to ensure the laser transmission efficiency,increase the transmission capacity,and reduce the negative impact of the transmission process on the beam quality,so as to meet the application requirements of laser weapon,the key technologies of coupling and transmission for medium-wave infrared energy transfer fiber are studied in this paper.The main research contents are as follows:1.Research on the influence of alignment error on coupling efficiency and beam quality.Starting from the basic concept of coupling efficiency,based on the effect of longitudinal error,lateral error and angular error on coupling efficiency,the expressions of the three kinds of alignment error and coupling efficiency are derived.Simulation and experimental verification show that the obtained expressions have high accuracy.From the perspective of geometric optics,combined with the means of simulation,the effects of longitudinal error,lateral error and angular error on beam quality are analyzed,and the conclusions obtained are verified by experiments.In addition,the conclusions of the effects of alignment errors on coupling efficiency and beam quality obtained in this chapter are generally applicable to large core fibers.2.Research on bending loss and efficiency of coupling and transmission.The mechanism of macro-bending loss and micro-bending loss of fiber is analyzed from the perspective of wave optics and geometric optics.On this basis,the formulas for macro-bending loss and micro-bending loss are derived.The factors affecting the transmission efficiency of optical fiber coupling are systematically analyzed,and from the two aspects of coupling efficiency and transmission efficiency,a very comprehensive formula for calculating the efficiency of coupling and transmission is obtained.3.Research on the damage mechanism of infrared fiber and the meas urement of damage threshold.Based on the analysis of the main causes of infrared optical fiber damage,the damage mechanism of different parts of the optical fiber is further refined,and the damage morphology of fiber damage caused by different mechanisms is determined.The methods of damage determination and damage threshold measurement for infrared optical fiber are summarized and discussed.According to the analysis of the damage mechanism of the optical fiber,the vulnerable parts of the optical fiber are determined,and a number of measures for preventing the damage of the infrared optical fiber are proposed.4.Research on the technology of cladding light stripping and end cap.The causes and effects of cladding light are analyzed,and the necessity of cladding light stripping is clarified.The fabrication methods and processes of various cladding light stripper are summarized and compared.The optical fiber end cap and its fabrication method are discussed.The scheme of optical fiber end cap participating in laser focusing is proposed,which improves the performance of coupled optical system significantly.5.A design of a connector suitable for the connection of medium-wave infrared high-power non-fiber lasers and energy transfer fiber has been completed.Through the analysis of coupling method and specific design requirements,the design of the focusing optical system is completed.The analysis shows that the optical system has excellent focusing performance.According to the optical design results,combined with the analysis method of simulation,the structural design of the connector is completed,and the positioning accuracy and working stability of the connector are improved.The active water-cooling circuit is designed to protect the connector effectively and prevent the damage in the process of high-power laser transmission. |
