A system for launching flyers using a Q-switched Nd: YAG laser has been developed for shock initiation of secondary
explosives. Flyers have been launched at velocities approaching 6 km s-1. Optical fibers are used to transport the optical
energy from the laser to the detonator.
The launch of these flyers with sufficient velocity requires a fluence in the region of 35 J cm-2, significantly above the
damage threshold of most optical fibers. This damage is typically caused by laser absorption at the input face due to
imperfections in the surface polishing. A variety of optical fibers with high quality input faces have been tested at
fluences up to 50 J cm-2, and their damage thresholds and beam profiles have been measured.
The standard fiber used in this system is a low hydroxyl (-OH) content, 400μm diameter core silica fiber, with CO2 laser
polished faces. In addition to this, fibers tapering down to 300μm and 200μm core diameter were investigated, as a
means of increasing the efficiency of the system, along with mechanically polished fibers.
The fiber currently enters the detonator body from the rear. Depending on the application, it may be required for the
fiber to enter from the side. To facilitate this, fibers with a machined output face, designed to produce an output at
approximately 90 degrees to the fiber axis were tested.
Finally, a 2:1 fiber splitter was tested, as a first step to enable simultaneous firing of several detonators. Multiple
initiation points are desirable for applications such as programmable initiation, and it is intended to study fiber splitters
with a higher split ratio, such as 4:1 and 8:1.
The results of these experiments are presented, and assessments made of suitability for transmission of high-power Qswitched
Nd:YAG laser pulses.