Fibre Energy Transfer Characteristics Of High Peak Power Laser Research

Delivery of high power laser through large-core optical fibers is an important technology used for applications ranging from laser weapons to laser processing and laser surgery. A typical military application that is motivating interest in high-peak power laser transmission through optical fibers is laser ignition. Currently the study on high-peak power pulsed laser delivery through large-core optical fibers is rare, which is the designing foundation of laser ignition system.The thesis focused on the characters of high-peak power pulsed laser injection, coupling and delivery.In order to research the characters of laser power transmission through optical fibers, firstly, laser ignition mechanism is summarized and anlysized, including ignition ways, system components, the relations between laser ignition performances and laser intensity, fiber core diameter. Then, the scheme of laser ignition system is designed. The optical path optimizing is an efficient way to miniaturize the system.The characters of laser coupled into planar-end and lensed-end fibers are investigated. A novel laser injection device is introduced and investigated. The cone of light can minimizes the injection laser power 4 times, which is validated by experiments.The characters of fiber-fiber coupling are studied by simulations and experiments. The relations between injection condition, fiber bending and coupling efficiency, laser power distribution are investigated. Nonlinear effects in fibers limit seriously to output laser power that is experimentally investigated.Reference on "GJB1487-92 test method for laser optical elements" and "ISO11245 test method for laser radiation induced damage threshold of optical surfaces", the experimental setup of laser induced damage to fibers, fiber damage judgment criterions and data processing methods are introduced and validated. The tested damage threshold at 0% damage frequency is 54.2J/cm~2 . The cause of fiber "entry" segment damage is investigated. Fiber end face damage shape and mechanism are studied particularly; the plasma generation is the direct reason of laser induced damage to fiber end faces.In order to satisfy laser ignition application and security, avoid high-peak power pulsed lased induced damage to fiber delivery system, a new ignition way, laser focusing ignition, is investigated, it can improve laser intensity more than 26.75 times.