Influence of Laser Beam Profiles on the Performance of Laser‐Driven Flyers

Abstract

In order to reveal the influence of laser beam profiles on the performance of laser-driven flyers, three different laser beam profiles including original laser beam, reshaped laser beam and optical fiber output laser beam were used to launch the flyer plates. The original laser beam showed plenty of "hot spots". A lenslet array was used to reshape the original laser beam and a much smoother intensity distribution was obtained. Both original and reshaped laser beams were coupled to optical fibers. Results showed that the laser energy that a fiber can reliably transmit increased 29 % and reached up to 59 mJ by reshaping the original laser beam. Furthermore, PDV measurements indicated that there was a 68 % increase in flyer velocity when the flyer was driven by a fiber coupled laser instead of the original laser, and the flyer velocity could reach up to 1.5 km/s when irradiated by a 50 mJ laser. Aside from the velocity increase, the fiber coupled laser was proven to be capable of producing controllable planar and intact flyer. A fiber coupled laser initiation system incorporating a laser slapper detonator was developed. The fine grain CL-20 was successfully initiated using the fiber coupled laser initiation system under 40 mJ laser energy, implicating the fiber coupled system is applicable in high energy explosive initiations.