Flexible and wavelength-independent optical transmission for laser pointing stabilization and assembly error...

A flexible light guide was developed for an ITER (International Thermonuclear Experimental Reactor) poloidal polarimeter which is a passive laser beam alignment and stabilization system for free-space propagation of a wide range of wavelengths. The advantages of using a flexible light guide are (1) to compensate the relative movement between the floor of a building and an optical table, (2) to negate assembly error of the optical transmission line, (3) to minimize the time required for assembly of the line and laser position alignment in a radiological environment, and (4) to transmit a wide wavelength range from visible to far-infrared. The authors fabricated a flexible light guide with an inner diameter of 120 mm and with a motion range of 10 cm. Pointing stability of the laser beam passing through the flexible light guide was less than 70 μrad when the support moved ±50 mm. A flexible light guide error of 70 μrad leads to a beam position displacement of 0.98 mm at a beam position steering mirror ITER poloidal polarimeter that is located 14 m from the flexible light guide. The achieved error is stable enough to guide the laser beam to its target in ITER.